Ported vs. Manifold Vaccum Advance! | Were To Hook It Up And Why | How Are They Different?
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- Опубліковано 23 сер 2024
- vacuum advance! do you hook it to ported / timed vacuum or manifold vaccum?
this is a long standing argument and conversation topic across the entire classic car community!
@thejunkyardnecromancer has called out me, @UncleTonysGarage, and @ThunderHead289 for being WRONG about using ported vacuum?
well if you want an ultimate performing experience I suggest using ported vacuum in combination with a curved distributor that has had its machanical timing limited so you can run higher initial timing!
with manifold vaccum when you hit the gas or go Wide Open Throttle the vacuum drops down close to zero and consequently your vacuum advance does as well.
wirh ported vacuum you dont have vacuum advance at idle, so if you run the initial timing higher with machanical when you hit the gas you will not lose all that timing to get you off the line!
also if you want a detailed video on how to dial in your vacuum advance check out @UnityMotorSportsGarage and @DavidVizard as they have videos showing you how to do the things I explain in this video!
#classiccars #ford #mustang #timing
Unplug your vac advance pod. Set your initial mechanical advance with your timing light. Then rev the engine to 3k and verify your max mechanical advance using the timing light. This is your base and max timing settings for WOT. Reconnect your vacuum advance to manifold vacuum or ported. Adjust idle and fuel mixture screws to fine tune your location. Both vacuum methods provide the same part throttle/ full throttle performance and MPG. The only difference with manifold vacuum is the extra timing at idle. Ported waits until just past idle to provide the same vac signal. Some engines like the higher vacuum signal from extra timing at idle.
Hi there what is the safe timing in degree at idle with vacuum advance connected to full vacuum.
@@ahmadaldahoud1719Good question
Changes with every engine combination
@@newguysgarage6802 for stock engine Chevy 350
@@ahmadaldahoud1719 If you have the timing right the vacuum will be high, if you go too far the engine will begin to run rough and the vacuum gauge will lower. If you go too low with the timing the engine speed reduces and the vacuum also reduces. Rule of thumb is 5-15 initial, 32-26 total and vacuum advance to taste based on drivability. That's why so many argue about it, they taste different. lol
Been doing it 40+yrs. You give an engine what it wants, generally speaking. Vacuum advance/retard was an original emissions reduction attempt. Manufacturers were trying to reduce HC during choke on warm-up so many set-ups routed manifold vacuum through a thermal vacuum switch, which blocked the vacuum signal until operating temp was achieved. Both ported and manifold vacuum were used on many set-ups. Ford actually had vacuum advance/retard diaphragms with 2 ports on the distributor back in the smog motor 70's. In the end it was all about reducing emissions and was a compromise. We usually used strictly mechanical advance on street/strip hotrod set-ups. Good rule of thumb is give as much advance as possible without detination, also a 5 gas exhaust analyzer is very helpful. In the end it's all a compromise, and is why we now have really fast computer controls for timing and fuel delivery. In
Agreed, you give it what it wants but Chrysler has been using ported vacuum since around 1939. Ford was also doing this within a couple years after ChryCo, and it wasn't about emissions. It was to improve drivability. It was devised to address the lean condition that would result during part throttle conditions that are common in street driving.
"Give it what it wants" That's a good "rule of thumb", I completely agree, but I'll add that you should either (if it's a factory stock, unmodified engine) give it what the engineers designed it to have, or (if it's been modified) give it what it wants.
"Vacuum advance/retard was an original emissions reduction attempt" No, I have to disagree with that one. Vacuum "advance" was originally developed (I believe in the 1920s) to reduce or eliminate knock by retarding the timing under moderate to heavy throttle back when gasoline was still basically a by-product of refining. For that purpose, manifold vacuum worked well enough, so that's just what most car makers used. After gasoline production was improved, cars continued to use vacuum advance because they still tended to knock when they reached high mileage (remember, 50,000 miles was considered high back then), and/or if the owner used cheap fuel. Also, as the commenter above pointed out, manufacturers began experimenting with ported vacuum long before anyone cared about tailpipe emissions, and they found that they could get better performance with it during the idle to part-throttle transition, just as it was explained in the video. It wasn't until the late '60s that they started experimenting with it in attempts to reduce emissions.
You summed it up perfectly when you said the engine doesn't care what you think, it wants what it wants. Very true.
After 2500-3000 rpm under load the argument ends and total timing is all that matters..
Good teaching! I figured all this out way back when i took off the goofy restrictor pod inline with the vac advance on the old 2.3 Pinto. When ya dealing with 88 hp, you can easily feel when that advance power kicks in. lol
Its night and day when you have some initial right off the starting line! 😁
I don't know what all you guys are talking about. I've been cleaning houses for 50 years, and there's been practically no advancement in vacuums. They all still suck.
Excellent excellent video! Just watched junkyards video before watching yours and he was almost there but not quite there. There are so many variables that you cant tell someone who doesnt know better that ported or manifold vac is better. Give your engine the timing it wants at any given rpm/load/ cylinder fill. Old school engine tuning is becoming a lost art. Good job my friend. Cheers
Thanks for watching both our videos 😃
It was a fun debate! 😁👌
On an 1971 LS6 454 corvette the vacuum is factory connected to manifold and the Holley carb does not even have the provision for ported on the metering block, hmmmmm, GM knows something we do not?
Alway connect to manifold if you have a long duration cam.
I think you nailed this..I have always leaned to ported..With manifold, you set your initial timing to 8 or so..Add manifold and now you have 20 degrees..Adjust idle screws and you have a purring engine...But what good is a purring idling engine...You put it in gear(Automatic) and the engine slows down..lose timing..and then take off the line..Lose all timing except initial..
Now instead of the above, set timing at 20..you never lose that ever..mechanical adds 12-14 more and off you go..ported comes in and you are cruising down the road..
When I set the timing at 20..set the idle screws and I will have that same purring engine but with more growl off the line!!
@@MichaelJohnson-cm4wp yes! Exactly 😃
I tried both on my Toyota 89 Hilux with 3y engine....with manifold vacuum after several thousand kms springs broke inside my electronic distributor while decelerating and with heavy load, dizzy destroyed. So never again. It's obvious that as you accelerate you need advancement of spark....pedal accelerate vacuum accelerate/advance....PORTED! But I agree that some stock carbureted engines are originally on manifold vacuum...Keep it as engineers designed it! Well explained sir
I'd use manifold vacuum advance if it works on your particular engine but sometimes doing that alone can cause a stumble when you go to accelerate, switching to ported vacuum advance will fix that.
Right on buddy! Like I always say , The engineers for Holley and Rochester got it right with PORTED Vacuum. Ported works for me and that's all I am worried about. Everyone else can tune as they please. The thing I notice most about the manifold vacuum enthusiast is they do not fully grasp all the scenario's of operation that you explained in this vid. Great Job .
Thank you sir! 😃
The point of vac advance is MPG and drivability. In the video that was recommended with David Visard he recommends manifold vacuum. Ported vac was for emissions, to retard timing at idle, its not so you get a big timing advance when you step on the gas. Tune you carb, accelerator pumps, power valves, jets, etc for the throttle response along with timing. Still a lot of good info here and gets people out trying things. I'll concede that in some cases the ported vac may accomplish just what you want, so its not wrong that's why everyone still cant agree:)
Best explanation thus far, I've always sworn that manifold was the way to go because the idle is so much smoother but i do have a little hesitation off idle. your video made a whole lot of sense. I have to re-evaluate my thinking and do some more experimentation, Thank!!!!
Thank you for listening! 😃
If you have stumble off-idle, depending upon what carb you are using, you need to 1st determine whether or not your accelerator pump is properly set. If yes, then an increase in jet size (or decrease in rod) size is your next step to enrich the transition from idle to off-idle. As to which vacuum port to use, if you have a pre-emissions engine, use manifold IF you have the original factory distributor and it was set up from the factory that way. As to fuel, you need to acknowledge that the fuel you use today DID NOT EXIST when your engine was designed.
AMC used something that perhaps was a little different. The AMC system switched from manifold to ported once the engine
warmed up to operating temperature for only one reason, to reduce emissions. That is why emissions engines run hotter; sometimes MUCH hotter, due to ported vacuum. This is especially essential for engines that have catalytic converters.
Some may disagree. Up to you to decide what to use. Do so at your own peril.
One final note; you might want to check out the CARB CHEATER from ThunderHead289. I'll be doing the same shortly, once I return home, as I am currently OCONUS.
I'm using constant velocity carburetors, there are no accelerator pumps.@@backthatthingupyoyoy
An old hotrod trick is to use a three way12 volt solenoid valve with a switch so you can switch from ported to manifold vacuum when stuck in traffic to help keep from overheating. Then switch back when finally moving. I use a Clippard three way toggle switch and connect the vacuum rubber tubes directly to the switch. Works great. 😊
I've recently got interested in manifold vacuum advance and thought I would experiment a bit. The engine I'm tinkering with is a stock 1974 Chevy 350 small block. When I set the initial timing by vacuum it idled best at 23 deg's, at around 700 RPM. Purrs like a kitten and is very responsive. At this setting the mechanical advance carries it to 36-37 deg's for reference. For clarity, no vacuum canister input with these numbers.
The thing I noticed the most was it's immediate response to throttle input. Not the slight ramp up you get when a ported advance has to build vac / advance. My current thought is with full manifold advance the advance is in the system and on throttle lowers to match what a ported setup has to create. So its response would be faster as it didn't have to create advance from scratch. It's not that you initially lose vac advance on manifold but reduce it to equal what ported vac has to generate.
Ok, so how could I utilize that stored manifold advance for faster low end response? My thought is to back the initial off to help with starting, and using an adjustable vac canister, add the small amount needed to reach the sweet Idle spot of 23 deg's (on my engine). That would be near initial on crank and immediately 23 deg's on run / idle.
Manifold and ported setups should equal / balance at at partial throttle positions, though manifold advance would be capped at the idle tuning. Ultimately, a WOT requires the retarded timing delivered by the mechanical and there is little to no vacuum advance input.
Again, this is just a hook up theory I plan on testing. My guess is I will fined a faster low end response and smoother Idle, but less fuel economy than ported due to a richer trim and less potential advance in the mid range.
I'm not seeing anyone really demonstrating the technique of hooking up a manifold vac system online. Most people just point out the source and relationship of manifold and ported. Nothing ventured nothing gained, I'll give it a go and see what happens.
An old hotrod trick is to use a three way12 volt solenoid valve with a switch so you can switch the vacuum advance from ported to manifold vacuum when stuck in traffic to help keep from overheating. Then switch back to ported when finally moving. I use a Clippard MTV-3 three way toggle switch, 10-32 to 1/8 inch barb connectors and connect the vacuum rubber tubes directly to the toggle switch. This way there is no wiring involved. Works great. 😊
Timing and Vacuum Advance 101 by John Hinckley is a great read on this subject. Explains everything perfectly in a 5 page article.
I'm using ported. My buddy has a similar build but he uses manifold.
Some vacuum advance unuts actually are adjustable they have an allen screw inside the vacuum port
Some adjust total vacuum advance and some adjust the rate it comes in so got to make sure you know what one your getting lol
Outstanding explanation.Good job!
Thanks 😁
I've used both depending on what it likes. Whatever works best for you. Most of mine run ported.
I already have what you said about 8 initial timing at idle but that is only with my vacuum unhooked, with vacuum hooked up I have 22 at idle and 22 when cracking the throttle blades open I have a special setup, I am hooked to both ported and manifold, each hookup has a hose and check valve going to a tee, the tee is hooked to the distributer the vacuum is locked between the check valves and distributer with an aquarium air regulator valve on that line as to have just enough vacuum leak so that the vacuum can drop back down when the engine is turned off, it works great.
I think I will install a vacuum gauge in the near future. Then I can really know what's going on under the hood. My engine pulls really hard all through the RPMs and I limit it to 5400. But more Free power is always welcome. 👍
Invaluable tool to have! 😁
Take a close look at your vacuum canister, some were calibrated for manifold (typically pre-60's) and others were calibrated for ported vacuum.
Connect the canister accordingly, for best results.
Best video on the internet bar none on this issue and great explanation 👍
I tried 😂
i would have thought you would use ported for more timing when you take off? i have tried both on mine it is more sluggish hooked up to full vacuum when first take off so i have mine on ported dizzy set at 18 initial 34 total
Yep!
Thats the way I would do it 😁
Watch David vizard and Andy from unity motorsports garage explain manifold timing. Manifold vacuum is the way these systems are designed to run.
As a side note, I appreciate your pictures showing the piston skirts in the right place. 😉
I’d like to see you start that thing hot @22 initial timing. I guarantee you my engine won’t but it starts great at 10. Also your vacuum advance doesn’t need full vacuum to start pulling in timing so even when you punch it your mechanical advance will start before you loose all of your vacuum advance. Anyway not trying to bust your balls I just think this is a little more complicated than always use ported vacuum.
Agreed 100%.
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Here is me hot starting it at 18° which is not very far away from 22° lol
I love this stuff way above my pay grade though. Just keep it civil no biting. To your corners and come out swinging.
Lol 🤣
And no ear biting.
@@robertwest3093 ya you animals that will cost you 1 second off your time.
Take the fun right out of the game why dont you 🤣
@newguysgarage6802 Hey, I did not say anything about hair pulling or a finger in the nose tug, lol
I have seen cars fall flat when they step on it, it loses the vacuum and timing. ,when you use ported it won't fall off and will run correct
timed my 440 the same way had one setting for cruse and one for track never had spark knock, well there was the time someone filled the tank with 87 octane instead of 93!
Good job explaining. The part about the Ported adding timing, right when it seems to need it most, has been my experience. Swapping to Manifold ... I feel like i lost some low end grunt, and the motor felt more doggy. WOT, was no different.
Thanks! 😃
Thank you Dan for all your performance tips you give we could only hope that our cars run as good or are as fast as your red mustang is 😂😂😂
Eventually man if you keep at it!
I use a vacuum gauge to check for plugged catalytic converters too the normal response when you open the throttle is to increase vacuum but with a plugged converter the vacuum will actually become a pressure as you try to rev the engine from the exhaust backing up into the intake manifold the car will usually idle fine but fall on its face and stumble when you try to rev it
Vacuum guages are magic 😃
Well said!
Make up your own mind.. 👍
Camshaft profile determines how much air /fuel mixture, then bore n stroke then determine just how much can be sucked into the cylinder.
Size of valves etc
Yep! Every engine is different lol
Even down to how well the rings are sealing 😁
@@newguysgarage6802 so much goes into what makes an engine run at peak performance truly amazing,
@@dennisrichardson2577 and everyone has an opinion on every aspect of it 🤣
I think the MSD pro billet distributor should be added to theory. Which doesnt use vacuum.
But softer or harder springs and a start and stop point (curve) and once that science is agreed upon Switch to propane fuel which requires a quicker burn rate.
I like the vacuum gauge demonstration it makes it easy to understand what's going on I tried both and ported had more of a performance feel to it although I noticed other things ported as well .
The engine is 50% louder at idle at startup.i noticed water vapor and drips from my exhaust of course slightly hotter at stop lights in the summer . Full manifold it was harder to start after it was operational temp , quieter , but I could not get it past 12:70 ish on the AFR at idle it wanted a rich idle like 12:50 in drive 600 RPM . Ported I can go 13:80 AFR at idle no stumbles or hesitation and with the same jets the cruise AFR is leaner .
Thank you for watching!
Cool that you came to the same conclusion with your own testing as well 😃
Faster or slower burning?? I always thought that was relative to Octane. Lean burns hotter and rich burns cooler.
The Ford dizzy you have with the bolt on vac canister fitting if you pull the hose off you can put an Allen key into it and adjust the vacuum advance limit also. Just saying.
Not on my distributor there is not lol 😆
But yes you can get them to were it will either limit total vacuum advance or adjust the rate it gives it lol
I own about 5 cars all carb. And run. Both timed and manifold vac. Amongst all
Yep, very confusing on this ported vs manifold. Glad I have mechanical advance. And who is junkyard? thanks
He is another youtuber, one of my friends lol 😆
We had a disagreement on which to use so we made videos about them both 😁
@@newguysgarage6802 Oh Ok, I got it! TY Lots of arguing over this which one to use. lol
The answer for the correct vacuum source is, it depends on the distributor vacuum can pull-in calibration. Connect the can accordingly.
The HEI on my daily driver uses electronic advance controlled by the "rudimentary" PCM, there is no vacuum advance canister.
The canister on my 60's Chevelle pulls in completely with just a few inches of vacuum, thus it's calibrated for manifold vacuum
My advice is, you don't want to connect your canister willy-nilly.
LOL, this and kickdown adjustment is why we used to kick your butt with our "turd" from the stoplight.
These types of things are exactly why ive always beem terrified to touch a carb. So scared to completely fuck everything up. I really want to learn to tinker with them, ive always loved old cars-seriously all my life. Sadly, I can work on a newer car more easily than an older one. Its hard to find people who will teach you about these older systems and for it to make sense. Can anybody recommend a good book to read up on and a place to start to learn?
I think the question is also - when do you actually leave the starting line from idle?
Stop lights, stop signs, and traffic lol 😆
Maybe I'm missing something. If more cylinder pressure requires less timing, wouldn't flooring it from a dead stop be the highest cylinder pressure? And if so wouldn't (in theory) you need less timing right off the jump?
No because flooring it from a dead stop kills the vacuum and the velocity going through the engine, the engine needs to get higher in the rpm range before it can efficiently get fuel and air into the cylinder increasing cylinder pressure (volumetric efficiency)
Especially if you have a cam, headers, high flowing heads, intake, all of that stuff makes power at higher rpm usually trading bottom end performance.
@newguysgarage6802 Thank you for the reply. Just trying to get a grasp on this
Winner winner elk-steak dinner! This was a fantastic rebuttal. KUDOS!
Thank you! 😁👌
My question with manifold vacuum would be why would you want more advance on idle and start up. I’d rather have less for easier hot starts and smoother idle myself. Then better driving timing as soon as you tip in.
The bigger the cam the more initial timing your going to want because the lower volumetric efficiency there is lol
Ive run up to 18° initial so far (going to go further once I figure out a way to limit the advance more permanently on this distributor) and had zero problems with hot starts.
Partially flood the engine before you try and start it hot (3-4 pumps of gas and hold it down about 1/4 throttle and she should light right off)
@@newguysgarage6802 my old 327 had that issue. Too much initial and it would hard start. Some guys used to have to get them cranking and then flip the ignition on or they’d break the ends of the starters. It was the old press on balancer and it had spun. I honestly didn’t have the know how to use a piston stop back then so no clue where my timing was actually at. It was a balancing act with always a bit of sacrifice somewhere. Long story short I would have probably had to give up more if I used manifold vacuum. Maybe a bit too much compression for the street. Now I’d put a gear reduction on it and put the trigger for crank on a retard for nitrous. Ignition boxes didn’t have that option back then though. Not in my budget anyways. If you had the timing where it would start nice it idled a lot nicer too.
You want more advance at idle because the cylinder pressure is low resulting in a slower moving flame front. You have to account for that by advancing the timing. This results in a more efficient and MUCH cooler running engine at idle and cruise. Manifold timing is where its at. You just have to make sure that you have a properly adjusted vacuum advance canister and that your mechanical timing comes in quick enough to take over when the manifold vacuum drops. This way all three forms of timing are performing their proper and distinct functions.
@@yeboscrebo4451 more timing at idle results in harder starts. Especially with high compression and a rougher idle. As the rpm advances you add timing to make up for piston speed. To have that low of compression at idle you’d have to have ALOT of overlap. But then you’d be running big compression anyways.
@@chevy6794 if you have hard starts you need to drop initial timing until you don’t anymore. Manifold vacuum advance from the vacuum canister is specifically for the necessary timing advance at idle and cruise where decreased cylinder pressures require more advance. The mechanical timing from the distributor is specifically for the advance needed as rpm increases. All three forms of timing have distinct functions. Manifold vacuum advance allows them to perform those functions the way they were originally designed to.
I’ll jus leave this here. Edelbrock llc brochure #63-0061 page 8. Long duration cam “ if the distributor is fitted with vacuum advance unit, connect it directly to manifold vacuum.”
Thats only a bandaid solution that anyone can easily do.
The correct way is to recurve the distributor and use ported but that is not something the average Joe can accomplish on most distributors lol
I think you proved me right bud! You never explained why you want more timing off the line! You in fact want less as soon as you fill your cylinder like you said at the beginning!
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Why dont you put your theory to the test, I did lol 😆
@@newguysgarage6802 I will! There is one problem with your test though! You ran ported vacuum advance the whole time. If you would have used manifold vacuum, you would have got better results. ;)
Oh junkyard lol
I guess ill have to make one more video dashing that last hope you have 😂
@@newguysgarage6802 I need to make another video now too!
Yes!
"Ultimate performance! Is 8° or 22° initial timing better when the light turns green?"
There is your title 😏
Full manifold can help with idle on some cars , ported is usualy better if all is corect or even better set your dizzy up without any of them corect intial and total timing and lose the hassle of vac can
And lose 5 mpg!
You just gave my cousin two stickers of your channel near a fireworks tent!
Damn straight I did! 😁👍
I much prefer the idle with manifold vacuum because it runs much smoother and cooler especially on those hot summer days in traffic. I've been trying to come up with a solution to make manifold vacuum work.
The problem with manifold vacuum, is that the timing drops out and cause stumble and hesitation off idle and on acceleration.
I found a solution and it works perfectly. I installed an adjustable restrictor valve in the vacuum hose to the distributor and it allows the timing to drop out gradual as apposed to abruptly and that fill the gap in the delay of the mechanical timing. Been fighting this for 3 years now trying to find a solution and this is it. The difference is like night and day. throttle response is so snappy now and no stumble off idle. Car is a lot more fun to drive now.
Also installed a vacuum gauge on the distributor side of the valve in the cockpit to monitor the vacuum drop rate and and make adjustments as necessary.
Let me know your thoughts....
I mean...if you wanted the perks of manifold vaccum at idle but not the downfall of it dropping off....then using ported and just having higher initial timing does that already? 😅
But with manifold vacuum, timing is much higher in turn a much smoother and cooler running at idle and engine stars much easier without kickback. engine runs much better in every aspect. I've tried every combination and this one works best. how about you give it a try before you dismiss it, I'll bet you'll be surprised.
@lucsavoie9501 what is your initial timing at with the method 🤔
I road tune, just checked it, 10 initial, 32 all in at 2200, 'at tad early' and 30@ idle with vacuum advance.
@@lucsavoie9501 ok wait, so you have 30° at idle and 32° total?
Kinda sounds like your running locked timing then right? Just trying to understand what is going on 🙂
Because the machanical timing is bringing in basically as fast as the vacuum is dropping off with your check valve right?
Why would my ported vacuum be a 10 inmg at idle
I have a 1982 Z28 Camaro sbc 355 with a th350 transmission and a vacuum secondary Holley 750 I believe…
Help me out here what should I do to make a bit more snappy and reliable at lower throttle still running ported makes good ish manifold vacuum and 55psi of oil pressure any suggestions appreciated…
Bump up initial timing would wake it up, and a mechanical secondary carb would as well 😁
All you guys really like to over-complicate this issue. Why can't you set 22 degrees mechanical plus manifold vacuum advance? Give it more advance at idle! You just proved that it liked it with your vacuum pump test.
My decently cammed 383 idles better with 36 degrees total (manifold+mechanical) than it does with only 22. It idles way cooler too. Which is a big deal in AZ.
Then just give it 36° initial machanical and lock the distributor and use ported. That way you can keep the timing when you hit the gas.
22° was just an example 🙄
@@newguysgarage6802 But then I would have starting issues with kickback on the starter. I might also have pinging issues if I give it some throttle at low rpm. I don't want the full 36 degrees until around 3k rpm to avoid pinging.
Good timing for this video (pun intended). I had my Buick 455 at 20* initial, 14* centrifugal, 34* all in by 3000 and manifold advance with another 10*. I finally ripped the nose off my starter as a result doing a hot start leaving a gas station about 1000miles from home. Got it to the AirB&B, got a starter from NAPA and now I’ll run it on ported vacuum for the return trip. It starts easier now, but idle in gear isn’t as good as before.
Lot of times in order to run higher initial timing you need to either
Pump the gas 3 or 4 times to partially flud the engine so it has to spin a bit before it lights
Or have a ignition switch that you flip on once you get the engine rotating 🙂
@@newguysgarage6802 I tried that, UTG had a good video on it a while back, but it would just launch a massive backfire out the exhaust, blew a hole in the muffler last year trying it. I was able to fire it hot without touching the gas for several years without issues. It was just a bad hot start in the wrong conditions.
@@keithiverson6687 ahh ya things just happen sometimes 😁😅
@@newguysgarage6802if you have to do that it's not right.
You have a lot of practical learning to do.
About twenty years ago I was sure I was right doing exactly what you're doing.
Eventually you'll get there....
Sometimes you have to tune the vacuum advance also. By limiting the amount of advance it can add at full vacuum for whatever the engine has. I run manifold vacuum now on my cars but I always check the vacuum advance travel with a hand operated vacuum pump to see how much it travels. Then I see what the max vacuum my engine produces and adjust it accordingly. By modifying the vacuum advance canister. I get great gas mileage now compared to running it ported.
I stopped using vacuum advance a long time ago with hotrods. A built motor in a 3000lb or less vehicle has no need for it. Just like he said give it all it can take without detonation and lock it down. Any car I ever worked on that did run vacuum advance I used the ported vacuum and had initial timing around 15 and never had a problem.
Vacuum advance is really for fuel mileage mostly......but you defenatly get significantly better millage with it on 😅
I'm just talking about stop light cars with the first bit. Having a locker is already crushing my mileage anyways.
That is true lol
I run an open diff, but I have the rear end set up so it will burn both tires every time.
Same thing as having a posi but way way cheaper to do and pull off lol 🙂
@@KCDW83 I agree with what YOU said. Mechanical setting and advance is what is important- especially with an automatic transmission. But it surely doesn't hurt to add some vacuum advance supplied by the ported source for light throttle street driving. Something that hasn't been mentioned, though, is the type of carburetor being used. Unless using an actual performance carburetor and knowing how to tune it, intake manifold sourced vacuum may be needed as a "crutch" for acceptable idle and light throttle operation. As for initial timing settings, a lower compression engine with a performance cam will need much more initial timing than a higher compression engine with a milder cam. The low compression cammed up engine will usually be a dog at low rpm and hard to get a good idle in gear with factory spec initial timing. Adding manifold sourced vacuum advance to advance the idle timing won't help much because when you step on the pedal that timing falls out. Also, when you put an automatic trans in gear the engine vacuum is reduced and the rpm drops even more so that you may have an idle speed of 1100 rpm in neutral and still have a hard time of getting 800 rpm in gear. On the other hand, an engine with with a very mild cam and a higher cylinder pressure may gas ping at low rpm and ruin starters with the initial timing that would work great for the cammed low compression engine. Manifold vacuum may be necessary for some factory stock or less than optimally tuned carburetors and mechanical timing/advance systems but one size don't fit all. If you actually NEED vacuum advance to make your vehicle run acceptably then you're not doing something right to begin with. Manifold vacuum advance can be helpful with manual trans vehicles. It can also cause a sag or a flat spot, though, if used unnecessarily. All said and done, I tune with springs, weights, and limiters and add some (usually ported) vacuum advance when vacuum advance is desired. Most of the vehicles that I work on are "toys" and fuel economy isn't the primary concern unlike days gone by when they were our everyday transportation. Something seldom mentioned is that a generous amount of ignition timing makes an engine run cooler, so that's something to inflence the use of vacuum advance.
Great video. I have a 65 c10 with mild cam and edelbrock carburetor. I have 12 degrees before tdc and 35 degrees advanced. I can only get 14 pounds of mercury from vaccum gauge. I have checked for vaccum leaks using propane tank but can't find any. Truck runs great but I feel I could get higher vaccum but don't know what else to do. Any suggestions would be appreciated. Thanks
Thats about all mine has too. Just the nature of having a mild cam 😅
Other than raising the idle RPM which would get you higher idle vacuum 🙂
1982 z28 Camaro auto 355 sbc help me out here vacuum secondary Holley aswell
Help you out.....with what? 😅
Put a mechanical secondary on it for starters! 😁
I understand your explanation about tuning to the highest vacuum. But you’re only tuning the idle mixture. Once the throttle blades open the idle circuit is no longer being used. Again I get your explanation but that only works to tune idle mixture.
Tuning to the highest vacuum also works on the road under crusing conditions.
Look at the Andy Woods video I referenced to learn how lol
@@newguysgarage6802 okay I’ll check it out.
@@newguysgarage6802 okay I watched his 2 part series and never was idle mixture tuning brought up. What am I missing here? I get his vacuum advance curve tuning. It makes sense and I plan on using his technique. I’m still a bit at a loss of why you are talking about idle mixture tuning. I’m sure I’m missing something.
@@newguysgarage6802okay… I get what you’re saying now. You’re just using the carb as an example to make the point of VE. Sorry it was early 😂😂
No problem 😁👍
Ya it was the easiest way to show what the vacuum guage would do lol 😅
Team ported for the win 😊😊😊
Depends on what kind of setup you are working on. You make it more complicated than it needs to be.
I don't think manifold vaccum goes away during part throttle acceleration does it? Your accelerating at part throttle and the engine speeds up so if your not WOT, the vaccum should increase with engine speed. In this case, if you have a fast acting mechanical advance coming in and the manifold vaccum advace slightly decreasing, its almost doing the same thing as having ported vaccum advancing the timing til the mechanical advance. I can see an examlpe for a setup running manifold vac adv. Set your initial at 10-12deg, 10-12deg vac advance, 20-25deg mech adv starting to come in early at say 1200-1500 rpm and all in by 2500 rpm. In this case, you start at under 20deg durring cranking, idle at 20-24, PT acceleration in the high 20's low 30's, WOT in the mid 30's, and highway low load cruise close to 50deg. Just spit balling. What you think?
I think all acceleration is wot acceleration so manifold vaccum wouldn't work 😂
I have used both but I'd rather lock it out than use manifold. I have a pre-government gutted 67 Buick that doesn't even have a manifold port on its original Carter. Even has the original vaccum line on it and points distributor. It really depends on the build.
You can add ported vacuum on top of locking out the distributor to get best of both worlds!
Just need an adjustable vacuum pod though lol
I wonder if this would have anything to do with my pipes glowing while cruising, lol. Ive noticed the floor getting hot but the engine temp would stay relatively cool. My friend was following me one day and claimed to have noticed my pipes glowing a little. Could the wonkiness of the vacuum advance cause it to burn lean while smelling rich?
Yea it absolutely could!
But its too late at night I cant think straight enough to take a guess why 😅
@@newguysgarage6802 Thats cool man, we both are up a bit too late, lol. Just something i was curious about that the internet cant provide a straight answer for.
The low cylinder pressure at idle and cruise make for a slow moving flame front. With ported timing, the timing is not advanced enough so that the flame front actually escapes the exhaust valves at idle and cruise making the exhaust loud and hot. Put it on manifold, readjust the initial, the vacuum canister and the mechanical timing and you’re good to go with a cool, more efficient running engine
@@yeboscrebo4451 My problems Went away when i switched to ported from manifold. Better economy and better power with no bogging down at take off and the floor doesn't get as hot as before. I literally couldn't floor it when the advance was on manifold vacuum because once it reached a certain RPM, i would lose all power, now i gain more power after i reach that RPM.
@yeboscrebo4451 just increase the initial timing lol 😆
A lean mixture burns faster and requires less advance. A rich mixture burns slower and requires more advance.
Exactly what I would expect from someone getting information on line and having a brain.
I....I think that's a compliment? 😅
@@newguysgarage6802I laughed way too hard at this!
Ill be doing one like this soon. You gave me some ideas.
Sweet! 😃
Both vizard and andy from unity motorsports both say monifold vacuum is the way to go. Andy has two videos on this subject in both he uses monifold vacuum. Maybe you should watch them again
Ive seen them, but they never discussed curving the distributors machanical advance in the video which you need to do running ported.
I referenced there video in this one to show how to go about finding what timing the engine wants by using the brake bleeding pump.
It just funny how you reference them in your video supporting ported vacuum when their videos specifically say monifold vacuum is the more efficient vaccum port to use and how to adjust it. For better fuel mileage and cooler cylinder head temperature.
Am I not allowed to agree with parts of people's opinions and disagree with others?
I agree with the method of finding what timing the engine wants, and disagree about using manifold vaccum.......is that not ok? 😂
To each is there own. It is a good topic to have a discussion on. Lots of good points made on both side. My vote goes to monifold vacuum.
Too much ign timing causes surging at light crusing speeds.
Too much is wildly different for different engines lol
Msd instructions says to connect to ported.
I used a T fitting and hooked it to both.
I win.
Hooking it to both.....is basically just having manifold vaccum 😅
And in actuality that would create a vaccum leak because air would be able to bypass from the ported port above the throttle blades to the manifold port below them....aka vaccum leak 😂
Lock it out at 36 deg.
Then add ported vacuum with an adjustable vacuum pod for the fuel mileage!
An animal off the line and will still cruise good 😁👍
Where are they hooked up from the factory?
60s and up cars, from ported lol
This is real simple. A vacuum advance is for gas mileage only. Drag motors have no vacuum advance. The timing curve is in the mechanical advance. When you Cruse at light throttle the vacuum advance needs to kick in. Manifold vacuum. If you Hook it to ported vacuum it destroys your advance curve and when you level out it retards and doesn't help fuel mileage anyway.
Go ported in my opinion...
That's what I think too, then just up your initial timing by limiting your machanical lol
@@newguysgarage6802 I havent watched it yet, just saw the title
Ok watched it, nice depth you went into, yep David Vizard did a great vid on it, saw one years ago where UTG had the dizzy in the car with him hooked up to vacuum also, a couple years ago I played with the 389 this way, it responded way better to the ported after setting the timing to where the motor "liked it"
Yep! 😁👍
Sounds like it’s time to get David Visard involved.
That would be sweet! Lol 😁
Yes, and he will tell you,manifold vacuum only!
Junkyard called it his "theory." Well, opinions are like, well, you know, lets say exhaust ports. Everybody got one. Ported vacuum is the way to go for street. Period.
Thats what I believe anyway lol
The only difference between the two is when you hit the gas from idle, manifold will take timing away.....ported will keep or add timing.
So question is, does more timing off the hit = better performance?
I say yes 😃
@@newguysgarage6802 It's long proven, and a quick advance is ideal to maximize this. The ideal controller will actually roll timing back some at high rpm to maximize power on the big end as well simce timing requirements change at high rpm. This is like re-inventing the carburetor. Really don't think there's much else to be done. Little tweaks here and there, but really. Ported vacuum isn't for emissions. It's not the government. It's so me ply a method to more accurately provide proper ignition timing for the varying conditions street engines encounter. Racing is another matter. So, yeah. Can't believe the stones on that kid.
@tvdroid22 he is doing a test series to find out once and for all which one is best......all I need to do is sit back and wait for him to realize it on his own lol 😁
22 degrees ftw... I want the grunt off the line
Thats my choice too! Lol 🤣
Ported vacuum is not the exact opposite of manifold vacuum. Ported vacuum is low at idle and wide open throttle, and high at part throttle. Venturi vacuum is the exact opposite of manifold vacuum.
Ported vacuum is zero at idle lol
When you give it gas Ported goes up
And manifold goes down as soon as you wing open the throttle....in other words exact opposite of eachother.
You referenced Andy and David’s video but your conclusion differed from theirs. The mechanical timing for the distributor comes in just as fast as ported vacuum timing would off the line. If you’re set on manifold timing, mechanical timing should be set to come in quick and strong - that’s it’s designated job. The designated job of the vacuum advance canister is to give you timing at idle and low load (as you described). On ported you are allowing the vacuum canister to encroach on the mechanical timings territory and that overlap of functions just doesn’t make sense. Theres no need to have the vacuum advance canister helping out the mechanical timing with its job. The other thing I repeatedly see people misunderstand is that ported and manifold are NOT the same “as soon as you crack the throttle”. Just watch any demonstration where both manifold and ported vacuum gauges are side by side. Manifold vacuum is still high when the throttle is slightly cracked right where you’d be at highway cruise whereas ported is still low. The two don’t equalize until the throttle plate is more opened. This means more mpg and a cooler running engine at idle AND low load cruise.
Ya I referenced there video to find what your engine wants timing wise using the vacuum gun. Just because I agree with the method they used doesn't mean I have to agree with the conclusion they came up with based on that data 🤨
I agree with you for instance saying vacuum should have nothing to do with the machanical timing portion.....however it is manifold timing that actually does influence the machanical timing not ported.
When you set timing with ported you are not relying on manifold vaccum to bring in your timing when you launch the car, you are strictly running off machanical timing for that. Only time ported vacuum would come into play is at light cruise, otherwise you are using machanical timing for idle and stomping on the gas.
Your argument about how the machanical timing will come in faster than the manifold vaccum will die off is completely wrong however. Take a fairly heavy car with a tight converter and highway gears and it would not be able to accelerate the rpm fast enough to not be completely boned by the fall off of manifold timing off the hit.
That is not an ideal setup for a performance car no......but most people's cars are not set up ideally, so you need to take that into account.
If it was a stick car or has a loose converter then flip a coin because ya you can rev past the problem point before you leave the line. But tuning to manifold will only work under that condition.....tuning to ported will work for any condition. Therefore I deam it superior 🙂
@@newguysgarage6802 I’m sorry I can’t make sense of what you’re saying. “It is manifold timing that influences mechanical timing not ported”. Huh? A car set on manifold will have a combination of initial timing and manifold vacuum advance at idle. When you punch that throttle, manifold drops (to the same level as ported) and mechanical takes over where manifold left off (if you set it to do so). I know you know this so what am I missing? “Running off of ported Ported vacuum comes into play at light cruise?” Huh? When I’m flying down the highway with those throttle blades barely cracked, ported vacuum doesn’t really come into play until the tips of those blades pass the ported vacuum holes in that carb. You have all that space between where those throttle blades are shut and where they pass the ported vacuum hole where Manifold vacuum advance is giving you the timing you need for low load. Mechanical timing comes in as fast as you set it to come in - what are you talking about!? If you put dainty little springs on those weights they’d fling open instantaneously - you can’t get any quicker than that. There must be something I’m not understanding about your position because it honestly sounds like you’re describing ported when you mean manifold and manifold when you mean ported. I dunno
@@yeboscrebo4451 when you set your initial timing you are relying on manifold vaccum to take up the extra amount if you are using manifold.
If I want 22° initial and I use manifold I have to set my initial lower and have the vaccum bring it up the rest of the way.
Manifold vaccum is influencing with your machanical timing more than ported.
When you tune with ported it doesn't come into play with initial timing, if you want 22° initial you just set it there mechanically. So when you hit the throttle and your vaccum falls away you get to keep your timing.
Most people have there timing all in by 3,000rpm. If you have a tight converter and highway gears when you hit the gas to launch the car it will not fling up to 3,000rpm right way because it is under load it is trying to push through. In that senerio (which is the majority of the time with people's hotrods) manifold vaccum drops off way before your machanical timing gets brought in.
Were if you run ported then you can keep your timing during the hit.
Yes you can make your timing come in quicker than what the majority of people have it set to being 3,000rpm, but unless you are making it come all in at 1,500rpm you will still have timing taken away faster than it will replenish with machanical timing using manifold vaccum.
And really if your going to have it come in that soon....just run a locked out distributor, there are so many ways to get around the "hard starting" that its not even a factor really. And then you can add ported vacuum on top of that if you really wanted to for the light cruise down the highway. Just get an adjustable vacuum pod and your set lol.
@@newguysgarage6802 I see. Much clearer, thank you. I see now when you say that manifold vacuum advance influences your mechanical timing more than ported you, of course, mean that it indirectly influences mechanical timing. But ported vacuum advance DIRECTLY influences mechanical timing settings in the same way that manifold directly influences your initial timing settings. If you’re running manifold, you have to fiddle with initial and if you’re running ported you likewise have to fiddle with mechanical. So, I don’t see where you’re going with that one. And I just don’t agree that you can’t make the proper amount of mechanical timing come in as quickly as you lose manifold timing. You can have all of the appropriate amount of mechanical timing (relative to your rpm and load) almost instantaneously. If the engine isn’t reaching the 3000 rpm right away because of load, you don’t need 3000 rpms worth of timing yet obviously. Mechanical timing should be curved. Maybe our disconnect is stemming from the inclusion in your argument of race engine setups. My opinion (which is share with David Vizard) excludes purely racing setups (I think he said as much in his video). I could be wrong, after all i am fairly new to all of this. But I still don’t see the benefit of the redundancy between or overlap of ported vacuum advance and mechanical advance. To have all three forms of timing performing their distinct functions (initial, manifold vacuum advance for low load, and mechanical advance to match rpm) is so organized and clear to me. To have ported advance unnecessarily overlapping with mechanical advance seems pointless. To have the vacuum canister performing a redundant job with the mechanical weights in the distributor whilst the job it SHOULD be performing (low load/low cylinder pressure conditions) is ignored… seems very odd to me. As David Vizard said, these systems were designed for manifold vacuum advance. Ported came into the scene as a bandaid to account for new emissions regulations. I could be wrong though. The only issue that I can see which manifold timing doesn’t completely alleviate is the high rpm/low load situation that happens when you take your foot off the gas while you’re flying down a hill. But some pops out the exhaust aren’t going to hurt anything. Anyway, thanks for the clarification.
Im having a hard time trying to understand what you mean by ported directly affecting machanical I guess, I think this is were the disconnect happens lol.
After the throttle opens both manifold and ported are the same, when you punch it and go WOT they both are down twords zero and dont affect your machanical timing.
The only difference is at idle manifold has vacuum and ported does not, as soon as you start to open the throttle manifold vaccum goes down, ported goes up and they start to equalize.
That is the only difference lol
So not only does manifold vaccum have affect on your machanical initial timing....but it has the exact same affect on your machanical curve as what you are claiming ported vacuum is doing......so im not seeing how that is relevant?
Keep in mind the vacuum canister does not need full vacuum to fully activate, it changes from distributor to distributor but I know the one in the mustang is maxed out at only 8 inches of mercury.
This video proves you're wrong
ua-cam.com/video/Y69OGBb0GGw/v-deo.htmlsi=37vw9u5QXLRqD_hR
For those who don't want to watch it, the guy has two vacuum gauges side-by-side in his Dodge. One is ported, one is manifold. He films them as he drives around. Real world, simultaneous comparison... not blipping the throttle in the driveway. And it decisively shows manifold vacuum is the correct way to hook up. Manifold literally behaves identically to ported except that it also has advance at idle, which ported can't do. Manifold is also much more stable, which is going to be better under any circumstance.
Both right, both also wrong, for different reasons.
ua-cam.com/video/WD_bhDq_8tY/v-deo.html
TH explains it well, combining both points of view, but closer to the end explains why.
Great video could have taken your address off of the box tho
.....so? 😂
Anyone can find out were you live if you film outside, its not really a secret 😅
THIS THIS THIS !!!!! I'm sick of arguing with older dudes and younger dudes about this crap. Manifold vaccum is gonna take timing out when you hit the throttle and ported is gonna either keep your timing like you want it or it can add to it ( plays into how you curves your distributor weights and which vaccum advanced canister your using). Simple shit!!!. Too many Chiefs and not enough Indians out here with the wrong information and understanding.
Very easy concept to understand really 😅
I just watched his video and this came up right after. I couldn’t help but comment on how wrong his video was.
Lol 😂
Well this is they way that I see it anyway, just makes sense to me 😁
@@newguysgarage6802 that was a good half hour of free entertainment at very least. Simple answer is every combination will want something different. It’s good to have all these tools at hand such as ported vs full time. There’s no general rule. :)
22 initial timing is fine for an 8:1 compression ratio on a 2 barrel 289. Your starter will spin it. Try 22 degrees on a 383 with 10:1 CR and you'll break your starter or flex plate. Ported is for smog Era low compression non performance stock engines. Which wouldn't find itself on any starting line in any serious capacity. Use manifold vacuum with more performance oriented engines with higher compression, bigger camshafts and looser converters. Set initial timing at 16 degrees, set mechanical advance to be all in with 36 degrees by 3000 rpm. Limit mechanical advance to 36 degrees. After that hook up manifikd vacuum. You'll notice engine idles up so reset your idle speed at the carburetor. Now you have all that extra advance at idle to burn all that extra air/fuel mixture provided by that big camshaft. You don't want to add vacuum advance if your initial timing is at 22 degrees. 40, 50 or 60 degrees will cause pre-ignition/ pre-detonarion. This will bust pistons, spark plugs and head gaskets. The engine will tell you what it wants. Different engines want different timing curves.
No
Ima test this two theories of yalls as soon as i get my truck over here to play with! Lol
Im leaning more to @junkyard_necromancer though because your tuning to make it more efficient, not powerful your leaning it out and timing it untill its using all the fuel in the cylender sounds like your trying to be an emmisions controller! 😆
John 3:16
Its all about how the car jumps off the starting line! 😁
And manifold vaccum will take away all the timing you're trying to give it 😏
@@newguysgarage6802 I jus confused though, the way he explained it less vacuum equals more advance, the way you explained it more vacuum equals more advance??
So what I understand y'all are both right, but who has the rotation of the vacuum advance screwed up?!
@@OVERKILL_SS manifold vaccum GIVES advice when there is a vaccum at idle and low crusing speed. But when you hit the gas launching the car your vaccum goes down close to zero. Therefore taking away the timing the manifold vaccum was giving you.
Ported does not add timing at idle so when you time the distributor you can give it more initial advice to match what it would be with manifold vaccum.
But when you hit the gas during your launch, the timing stays because it was not the vaccum advance giving you that timing, it was your machanical.
@@newguysgarage6802 Uhh I needa watch his video again! Lol cuz I may have things mixxed up, I coulda swore he said vacuum retarded the timing so when you hit the gas it advances the timing. 🤔
Idk me cunfooseled I dont have a distributor to mess with! lol
@ShelbyScott919 oh ya no its vacuum advance as in advances the timing 🙂
Vacuum advice works up untill the mechanical advace takes over.
Hey brother your address is on the box just looking out for you
Ya I appreciate that!
I knew it could be seen but I've driven directly to the house on camera so it wasn't really a secret to being with 😅
@@newguysgarage6802 hell yea brother great information here. I removed the EGR on my 78 400 and put a edelbrock intake and carb and now the 3 way temp switch at my thermostat is incomplete and the engine idles high and pings idle once the temp switch engages, and it’s a slow cranked / hard start on warm starts. Would you say delete the temp switch and send the vacuum advance directly to the ported carb nipple? It seems my engine timing isn’t happy after my EGR delete once it advances at idle
@@Tyscrat if it were me.....that is what I would do lol
I would eliminate the complications and just go tried and true simplicity 😅
@@newguysgarage6802 you guys are saviors, nobody knows about these engines at shops. Only my grandpa and my 72 year old neighbor and you guys on UA-cam 🙏🙏 thank you I’ll subscribe