Back in the seventies, I ported a few cast iron sb ford heads. I was told for street cars not to touch the intakes but open the exhaust significantly. The results were tremendous. Woke the basically stock 289/ 302s up to the point that traction was an issue. After that I moved to fully ported 351 Windsor heads on the 289/ 302. The larger heads once again made all the difference, but they needed many more additional mods to hit their full potential.
Very interesting. It would be cool to see this comparison on a high compression engine vs a low compression engine. Initially I would think the low compression engine would see a greater benefit from exhaust flow improvements since it doesn't evacuate as well, but maybe the pumping loss of the high compression engine would see a greater benefit with less exhaust restriction.
Engines like the Cleveland and 429/460 Ford can gain serious power by modifying the heads to use the high port exhaust plates. And depending on the year, the stock exhaust ports have the A.I.R. port bulges. So yes, exhaust only porting will help quit a bit, but results can vary from engine to engine.
I am curious as to how much could be had simply by extending the exhaust duration on the cam of the unported exhaust port. Could a cam make up most or at least some of the shortcomings?
If you listen to podcasts at all there is a good one out right now from the go hard podcast. Its got Brian Tooley and Rick Smith(formerly of trick flow). They discuss a good bit about intake to exhaust ratio and their thoughts on how much it affects power. As well as a bunch of interesting stuff they learned from testing.
Eric, this is why I like your channel. I have been shouted down for saying there's power left in the exhaust port development on American aftermarket V8 heads. Why run a longer duration exhaust cam lobe to extend the rpm range when you can just develop the port? This gives you more options on cam timing and manipulating cylinder pressure. Get that port flowing a bit better and try a cam that opens the intake at about 30 degrees BTDC and opens the exhaust around 55 degrees BBDC (using .006 gross duration numbers, not the .050) Yep, you'll need about 15-20 degrees smaller exhaust lobe and a tight 105-108 LSA for it to work properly and probably 0 degrees of advance ground in. (try 280/260-105-0)You'll have a wide power band there. This isn't a new approach, Porsche's air cooled 911 engine has run like that for 50 years. It;s exhaust ports flow almost the same as the intakes. Pretty much the same with their 4 valve engines, I think. Get in touch with an old Ford drag engine builder named Ben Alameda on his UA-cam channel and ask him about what he does to the exhaust seats even though it kills mid lift flow numbers. There's a lot more to this. Cheers!
Dude when you fix or replace the dyno mule, just do a pull stock as it is, then do an exhaust port on those heads, then dyno that that set up, then go back and port the intakes and make another dyno run. Would be very interesting to see results that are apples to apples, too many variables with the test in this vid, I'm sure it made more power, but the amount is questionable in this vid.
Interesting conclusion Eric! These test results you're providing are invaluable for the enthusiast. My race engine days are well behind me now, but how I could have used some of this data back in the day. Over the years, I've heard that ex port shape* may be more important than actual flow bench results. ie: A better flowing ex port could be down on power compared to a lower flowing head. Makes sense due to the supersonic speed of the exhaust gasses compared to the flowbench airspeed... These test results invalidate that assumption somewhat. * A change in shape requiring more than could be attained with porting. ie: back in the early 1990's when the ex ports started getting really straightened out in new design race head castings.
Eric, I love your work. This is an area of expertise I have. What you will also find is gains in performance with exhaust porting and header length and diameter. Big is not necessarily better
I recall Mopr big blocks having weaker flow with exhaust port , i spoke once to owner of Indy cyl heads and asked about EZ heads and he said hold valve open for exhaust idk duration or lift but most cams use more lift for crutch?
BBM's Exhaust /Intake on the 906 heads was roughly 68%, OEM 2.08/1.74 valve size while 518 Max Wedge heads were 75% 2.08/1.88 , average Port job on the 906 heads 2.14/1.81 valve is roughly 70% Intake to Exhaust flow at .500 lift.. I can tell you on a 426 Street wedge(4.25 bore 3.75 st) cam was Mopar .654 Min express, Made 670hp @ 7200, with a set of OEM max heads, same short block with a set of Indy Cylinder head ported 915(same port as the 906, smaller combustion chamber) made 645hp@ 6900rpms. now this really wasn't Apples to Apple test, the max heads had a Holley Street dominator intake manifold that the port opens were welded up to match the larger Intake port opening of the Max heads while 915 heads used an out of the box Holley street dominator intake. Intake flow @.600 lift for the max heads was 295 while the 915 @ .600 was 313cfm. Dyno was a superflow 901. both used a Get'em garage 950 cfm carb and timing was 40* all in by 3200. Same Harland sharp rockers were used on both heads. fuel was local 100 oct.
Engine have a million mysteries on why they make power what's still goggles my mind there are people that still act like they done everything tested everything done it for 100 years and they actually like they know everything. Well here is 1 test we learned exhaust porting can help quite a bit obviously it's just 1 test. But yeah that's awesome and I just wish those 100 years of experience people can say hey I learned something I guess I don't know everything lol.
That is exactly the experience I have had in my dyno testing with exhaust flow and power curves. Darin Morgan has repeatedly stated that going from a 1.88 exhaust down to a 1.8 in a BBC gains significant torque under the curve and a prostock engine might use even smaller...
I too have seen gains from smaller exhaust valves. For 30 years, @ least, we've been fed that both valves need to increase in size together. The LS3 2.165/1.590 was my wake-up call.
Pretty interesting test. I think a better measure would be to make a dyno run with both intake and exhaust fully ported and compare to a run made with same head with only the intake ported.
So if building a street only very mild resto engine which doesnt see the high side of 5000 it may actually be beneficial to not fully port the exhaust but rather just give it a clean and do the seats. In the range of 2000 to 4500 your going to see torque improvements. Also dont run a split pattern cam with a longer exhaust duration. Very interesting test.
Very interesting test results. I know it could get expensive, but it would be interesting to see some results with doing a cam change, exhaust profile only, to take advantage of the improved exhaust. One would think that there is a formula out there to know how much to change. My train of thought, for what it's worth, is you would only need to reduce the duration split. Just curious. Would love to hear other folks thoughts on this, so I can learn and understand more.
My guess is that doing exhaust only will create vacuum which will increase air intake speed which will make more power by itself and in turn helps the fuel atomize better which also makes more power.
That wasn't the point of the video the point is how much gain could be possible when porting the exhaust port. Then what would happen if you did just intake or just chamber. Vs all off to see what made the bigger difference so we can all learn
no if by porting you mean removing material from the ports think Cleveland 4v heads which in many applications require material to be put into the inlet runners
It did as I expected it to do ... Exhaust flow along with camshaft is responsible of carryover or power around peak or just past peak HP .... It does this because you get a better cylinder blow down during the shorter time it has to do that higher rpm causes ....
Condolences on the loss of the dyno mule Eric. I'm suspecting that a portion of the power gains have come from a reduction in pumping losses on the exhaust stroke due to the increased flow
@racerd9669 you always have pumping losses on the exhaust and compression strokes. It's a physics thing and you can't avoid it. You can however minimise it.
@@theshed8802 Once you understand flow data , you can all but get rid of pumping losses by having the correct valve events. If you look at most engines guys build, just look into the intake track and you will see pumping losses by incorrect ex timing. Carbon in the intake is your first clue. And these engines alway run hot.
@@racerd9669 whats the relationship between manifold vacuum and pumping losses and exhaust back pressure and pumping losses? and why do several of the V8 engine manufacturers run cylinder deactivation instead of VVT to remove pumping losses?
I do wonder to do even highest of knowledge power know why certain things make more power and other things make difference or loss or whatever. Because it is so amazing what things happen in a engine when tested you man it gained but why it's crazy how stuff like this make you think twice on things but then you do it again it could be worse on other engines I don't know it's crazy
Based on the comments I see... The intake port is the "meat and potatoes" of the HP/TQ gains. However, if the exhaust is not addressed at the same time to support the increased flow, you are leaving some of the "meat and potatoes" on the table. In addition, valve angles, valve seat angles, intake, duration, lift are all factors as well. So, each engine (N/A) will have max potential HP/TQ for a particular setup. So the question I have is: What creates the true baseline of any engine, for an engine builder, to create a max/most efficient HP/TQ platform? Would this be bore, stroke, and compression? With an established baseline (whatever that might be), is there a natural progression and order of parts and engineering concepts, from which to work through? (i.e. Step 1, Step 2, Step 3, etc.) I have never seen an "established norm" for this, and I am sure this could be based on application; and additional goals. I am sure F1, Drag, Circle, Street, etc applications all have their own formulas; some the same, some not. Maybe some can write a book on this. 🤓
Different motor, but I used to clean up and mirror polish the exhaust ports only on my dirtbikes and atv's (2 stroke and 4 stroke), and they always picked up power. Also, I always had to go down on jet size. They always ran rich after this mod.
That was a very interesting result. I’ve never known someone to port just the exhaust side other than on small block Fords. There HAS to be a decent gain opening up that tiny port and removing the bump on the roof that blocks half the port off.
Hi Eric, ages ago you tested a head with a breakthrough and said it actually gained Hp with NO2, I think, did you ever figure out why? Really getting something out of your channel, thank you.
I'm glad you did this test Eric!! I've pulled 4x4 trucks since I was 16 years old. 47 now but I had a old timer tell me 25 years ago on heads to focus more on the exhaust port than the intake port.i always thought he was kinda goofy in his way of thinking. But I guess he must have been passing good information along lol.
Commenting at the start to see how wrong I am :p If you make the exhaust more efficient (and use a small enough header, off the head at least) you can make better use of scavenging, potentially using wilder cams than otherwise possible without losing lower in the rpm band.
I have suspected that porting the exhaust only would be beneficial, especially on turbo applications. My reason for thinking that is I can force as much air in as I want, but getting it out is harder. The engine is working against itself to push the spent gasses out, so it seemed to me that reducing that restriction would absolutely provide an improvement. I'd be interested to see what happens is only the intake gets ported. I know this test can happen due to the unfortunate demise of the engine, but if you ever get the chance it might be interesting. Thank you for what you do!
You are The Tech SuperMan!! That as always is a great informative Video. That would make another great tech video.That video dyno test now that you have exhaust port work, now the Intake porting and dyno testing to compare power output on each individually.
Hey Eric have a? I have a 434 with two valve leaf flat top pistons and for the heads I have a set of dart pro 1 that's port to 225 my ? Is will a set of AFR 245 work better?
I've seen it said that the vortec heads need the exhaust ported more than they need the intake side, that it is where the biggest gains would be found for the least expenditure.
Been there done that and retired ! 23 years ! Valve angle will be crucial and I started with iron heads unlike those who don’t touch them but come from a time that propelled me into the new heads with various valve placements and valve seat angles ! Ultimately cam shaft will be your learning process ! Personally afr heads are trash ! 🗑️
I did a set of iron head years ago with exhaust port work and it gains hp and torque. I recently asked on a head porting page about exactly this. No one new the answer. So thank you for confirming what I already suspected works.
I don't know, maybe the cam timing events are close and improving flow within those events is key. The power stroke stops when the exhaust valve opens, just like the compression stroke actually starts when the intake closes.
This is simple and you know this Dave. The size of the pipe and the turn of the pipe change how much it flows. You can make nice straight huge pipes on the bench but that is not how the headers are.
Although long-time Tradition, Why are Exhaust ports flowed at Same Intake corrected pressure (28, 25" water, etc) when the exhaust gas is thousand degrees Hotter with practically Zero relative mass Inertia & no Wet flow dropout componets compared to the much Cooler dense wet Intake componets ?? .....Just seems logical to Test flow the Specific port (Intake or Exhaust) closest to its average Running Psi & temps.....Would dramatically increase the flow bench Complexity but possibly increase the Exhaust port Flow measurment to Actual running dyno Tracking differences relationship....
Back in the seventies, I ported a few cast iron sb ford heads. I was told for street cars not to touch the intakes but open the exhaust significantly. The results were tremendous. Woke the basically stock 289/ 302s up to the point that traction was an issue. After that I moved to fully ported 351 Windsor heads on the 289/ 302. The larger heads once again made all the difference, but they needed many more additional mods to hit their full potential.
And doing the intakes made even more.
BTDT
Lee Shephard used to work hours and hours on the exhaust ports of the heads that were on the R&M camaro that wore #1 in pro stock for years.
Very interesting. It would be cool to see this comparison on a high compression engine vs a low compression engine. Initially I would think the low compression engine would see a greater benefit from exhaust flow improvements since it doesn't evacuate as well, but maybe the pumping loss of the high compression engine would see a greater benefit with less exhaust restriction.
Good information Eric.
Nice testing for sure.
Have not seen a test like this before.
Well done.
Thanks for sharing 👍 🏁
Engines like the Cleveland and 429/460 Ford can gain serious power by modifying the heads to use the high port exhaust plates. And depending on the year, the stock exhaust ports have the A.I.R. port bulges. So yes, exhaust only porting will help quit a bit, but results can vary from engine to engine.
I am curious as to how much could be had simply by extending the exhaust duration on the cam of the unported exhaust port. Could a cam make up most or at least some of the shortcomings?
If you listen to podcasts at all there is a good one out right now from the go hard podcast. Its got Brian Tooley and Rick Smith(formerly of trick flow). They discuss a good bit about intake to exhaust ratio and their thoughts on how much it affects power. As well as a bunch of interesting stuff they learned from testing.
Please try this on a set of small block Ford heads!
My first thought as well!
Yeah, I bet it’s worth a lot on a set e7’s.
@@jcnpresser
Lots of effort to not get as good as a stock P head.
Eric, this is why I like your channel. I have been shouted down for saying there's power left in the exhaust port development on American aftermarket V8 heads. Why run a longer duration exhaust cam lobe to extend the rpm range when you can just develop the port? This gives you more options on cam timing and manipulating cylinder pressure. Get that port flowing a bit better and try a cam that opens the intake at about 30 degrees BTDC and opens the exhaust around 55 degrees BBDC (using .006 gross duration numbers, not the .050) Yep, you'll need about 15-20 degrees smaller exhaust lobe and a tight 105-108 LSA for it to work properly and probably 0 degrees of advance ground in. (try 280/260-105-0)You'll have a wide power band there. This isn't a new approach, Porsche's air cooled 911 engine has run like that for 50 years. It;s exhaust ports flow almost the same as the intakes. Pretty much the same with their 4 valve engines, I think. Get in touch with an old Ford drag engine builder named Ben Alameda on his UA-cam channel and ask him about what he does to the exhaust seats even though it kills mid lift flow numbers. There's a lot more to this. Cheers!
Dude when you fix or replace the dyno mule, just do a pull stock as it is, then do an exhaust port on those heads, then dyno that that set up, then go back and port the intakes and make another dyno run. Would be very interesting to see results that are apples to apples, too many variables with the test in this vid, I'm sure it made more power, but the amount is questionable in this vid.
Only one variable on this. But maybe
Interesting conclusion Eric! These test results you're providing are invaluable for the enthusiast. My race engine days are well behind me now, but how I could have used some of this data back in the day.
Over the years, I've heard that ex port shape* may be more important than actual flow bench results. ie: A better flowing ex port could be down on power compared to a lower flowing head. Makes sense due to the supersonic speed of the exhaust gasses compared to the flowbench airspeed...
These test results invalidate that assumption somewhat.
* A change in shape requiring more than could be attained with porting. ie: back in the early 1990's when the ex ports started getting really straightened out in new design race head castings.
Eric, I love your work. This is an area of expertise I have. What you will also find is gains in performance with exhaust porting and header length and diameter. Big is not necessarily better
I recall Mopr big blocks having weaker flow with exhaust port , i spoke once to owner of Indy cyl heads and asked about EZ heads and he said hold valve open for exhaust idk duration or lift but most cams use more lift for crutch?
BBM's Exhaust /Intake on the 906 heads was roughly 68%, OEM 2.08/1.74 valve size while 518 Max Wedge heads were 75% 2.08/1.88 , average Port job on the 906 heads 2.14/1.81 valve is roughly 70% Intake to Exhaust flow at .500 lift.. I can tell you on a 426 Street wedge(4.25 bore 3.75 st) cam was Mopar .654 Min express, Made 670hp @ 7200, with a set of OEM max heads, same short block with a set of Indy Cylinder head ported 915(same port as the 906, smaller combustion chamber) made 645hp@ 6900rpms. now this really wasn't Apples to Apple test, the max heads had a Holley Street dominator intake manifold that the port opens were welded up to match the larger Intake port opening of the Max heads while 915 heads used an out of the box Holley street dominator intake. Intake flow @.600 lift for the max heads was 295 while the 915 @ .600 was 313cfm. Dyno was a superflow 901. both used a Get'em garage 950 cfm carb and timing was 40* all in by 3200. Same Harland sharp rockers were used on both heads. fuel was local 100 oct.
Engine have a million mysteries on why they make power what's still goggles my mind there are people that still act like they done everything tested everything done it for 100 years and they actually like they know everything. Well here is 1 test we learned exhaust porting can help quite a bit obviously it's just 1 test. But yeah that's awesome and I just wish those 100 years of experience people can say hey I learned something I guess I don't know everything lol.
That is exactly the experience I have had in my dyno testing with exhaust flow and power curves. Darin Morgan has repeatedly stated that going from a 1.88 exhaust down to a 1.8 in a BBC gains significant torque under the curve and a prostock engine might use even smaller...
Is that "gains significantly" below the torque peak?
I too have seen gains from smaller exhaust valves. For 30 years, @ least, we've been fed that both valves need to increase in size together. The LS3 2.165/1.590 was my wake-up call.
Pretty interesting test. I think a better measure would be to make a dyno run with both intake and exhaust fully ported and compare to a run made with same head with only the intake ported.
One of the most interesting videos I've seen in a long time, thanks for posting this up Eric!
Im not a big I/E ratio believer, but this was interesting. The engine wants what the engine wants.
So if building a street only very mild resto engine which doesnt see the high side of 5000 it may actually be beneficial to not fully port the exhaust but rather just give it a clean and do the seats. In the range of 2000 to 4500 your going to see torque improvements. Also dont run a split pattern cam with a longer exhaust duration. Very interesting test.
The meat and potatoes is on the intake side but gains available on exhaust too 😊
600 hp out of the AFR enforcers is impressive
Very interesting test results. I know it could get expensive, but it would be interesting to see some results with doing a cam change, exhaust profile only, to take advantage of the improved exhaust. One would think that there is a formula out there to know how much to change. My train of thought, for what it's worth, is you would only need to reduce the duration split. Just curious. Would love to hear other folks thoughts on this, so I can learn and understand more.
can you share the cam information? thanks
Has anyone heard of the conservation of matter? How about thermal expansion? Makes perfect sense improved flow on the exhaust makes more power.
So I guess porting my 56 374 packard cast iron heads is out of the question 🤔
Loving the info!
Make em as big as you can! It's gonna get out better, period
Looks like it's steam powered.
My guess is that doing exhaust only will create vacuum which will increase air intake speed which will make more power by itself and in turn helps the fuel atomize better which also makes more power.
what about better exhaust scavenging and less intake charge dilution ?
Can we assume that porting both intake And exhaust ports will make the most gains?
That wasn't the point of the video the point is how much gain could be possible when porting the exhaust port. Then what would happen if you did just intake or just chamber. Vs all off to see what made the bigger difference so we can all learn
no if by porting you mean removing material from the ports think Cleveland 4v heads which in many applications require material to be put into the inlet runners
I’d imagine this will be more significant with a supercharged engine.
Ya the supercharger will take care of the torque and the expelling of exhaust gas will help out a lot
Blowers in general like exhaust flow. We tested my f3-121 454 sbc before and after.
It did as I expected it to do ... Exhaust flow along with camshaft is responsible of carryover or power around peak or just past peak HP .... It does this because you get a better cylinder blow down during the shorter time it has to do that higher rpm causes ....
Condolences on the loss of the dyno mule Eric. I'm suspecting that a portion of the power gains have come from a reduction in pumping losses on the exhaust stroke due to the increased flow
or water/steam injection
Your valve events are incorrect if you have pumping losses.
@racerd9669 you always have pumping losses on the exhaust and compression strokes. It's a physics thing and you can't avoid it. You can however minimise it.
@@theshed8802 Once you understand flow data , you can all but get rid of pumping losses by having the correct valve events. If you look at most engines guys build, just look into the intake track and you will see pumping losses by incorrect ex timing. Carbon in the intake is your first clue. And these engines alway run hot.
@@racerd9669 whats the relationship between manifold vacuum and pumping losses and exhaust back pressure and pumping losses? and why do several of the V8 engine manufacturers run cylinder deactivation instead of VVT to remove pumping losses?
I do wonder to do even highest of knowledge power know why certain things make more power and other things make difference or loss or whatever. Because it is so amazing what things happen in a engine when tested you man it gained but why it's crazy how stuff like this make you think twice on things but then you do it again it could be worse on other engines I don't know it's crazy
Based on the comments I see... The intake port is the "meat and potatoes" of the HP/TQ gains. However, if the exhaust is not addressed at the same time to support the increased flow, you are leaving some of the "meat and potatoes" on the table. In addition, valve angles, valve seat angles, intake, duration, lift are all factors as well. So, each engine (N/A) will have max potential HP/TQ for a particular setup. So the question I have is: What creates the true baseline of any engine, for an engine builder, to create a max/most efficient HP/TQ platform? Would this be bore, stroke, and compression? With an established baseline (whatever that might be), is there a natural progression and order of parts and engineering concepts, from which to work through? (i.e. Step 1, Step 2, Step 3, etc.) I have never seen an "established norm" for this, and I am sure this could be based on application; and additional goals. I am sure F1, Drag, Circle, Street, etc applications all have their own formulas; some the same, some not. Maybe some can write a book on this. 🤓
Different motor, but I used to clean up and mirror polish the exhaust ports only on my dirtbikes and atv's (2 stroke and 4 stroke), and they always picked up power. Also, I always had to go down on jet size. They always ran rich after this mod.
That was a very interesting result. I’ve never known someone to port just the exhaust side other than on small block Fords. There HAS to be a decent gain opening up that tiny port and removing the bump on the roof that blocks half the port off.
Hi Eric, ages ago you tested a head with a breakthrough and said it actually gained Hp with NO2, I think, did you ever figure out why?
Really getting something out of your channel, thank you.
I'm glad you did this test Eric!! I've pulled 4x4 trucks since I was 16 years old. 47 now but I had a old timer tell me 25 years ago on heads to focus more on the exhaust port than the intake port.i always thought he was kinda goofy in his way of thinking. But I guess he must have been passing good information along lol.
Commenting at the start to see how wrong I am :p
If you make the exhaust more efficient (and use a small enough header, off the head at least) you can make better use of scavenging, potentially using wilder cams than otherwise possible without losing lower in the rpm band.
I have suspected that porting the exhaust only would be beneficial, especially on turbo applications. My reason for thinking that is I can force as much air in as I want, but getting it out is harder. The engine is working against itself to push the spent gasses out, so it seemed to me that reducing that restriction would absolutely provide an improvement.
I'd be interested to see what happens is only the intake gets ported. I know this test can happen due to the unfortunate demise of the engine, but if you ever get the chance it might be interesting. Thank you for what you do!
If you look closely at the dyno graphs, you also widened the usable power band. That's huge! Great video!
You are The Tech SuperMan!! That as always is a great informative Video. That would make another great tech video.That video dyno test now that you have exhaust port work, now the Intake porting and dyno testing to compare power output on each individually.
Show's take care of the Oz.The Ibs will take care of themselves.
Hey Eric have a? I have a 434 with two valve leaf flat top pistons and for the heads I have a set of dart pro 1 that's port to 225 my ? Is will a set of AFR 245 work better?
Do you think you could have gotten close to the same results with more exhaust duration?
That is awesome!!!!! I want to try this on my Ls3 heads!!!!
This was an awesome test, probably one of the most interesting ones I've seen yet. Thanks for the awesome content!!!!
That I have been wondering for a long time!!!
It helped us on a nitrous engine while it was being sprayed but I think our engine lost a little NA.
yes interesting ,,,thanks for doing,,sorry you lost a mule
I would like to see this test on a Ford head they are known for poor exhaust ports
Very interesting video, Genuine BS eliminator!
Very interesting, thanks Eric!
Great info. Thanks
Love this channel 😊
Now This is a Test!
Very interesting test
Fantastic info
Great info
I've seen it said that the vortec heads need the exhaust ported more than they need the intake side, that it is where the biggest gains would be found for the least expenditure.
So figuring out how to do a half fast porting job is worth the effort.
Please tell me how you get HP out off a oil pan ?
The reduction of windage
Been there done that and retired ! 23 years ! Valve angle will be crucial and I started with iron heads unlike those who don’t touch them but come from a time that propelled me into the new heads with various valve placements and valve seat angles ! Ultimately cam shaft will be your learning process ! Personally afr heads are trash ! 🗑️
Y do u say afr heada are trash
I use to port cast iron heads for years. Afr heads are proven performers. Not to say other heads are not better.
I did a set of iron head years ago with exhaust port work and it gains hp and torque. I recently asked on a head porting page about exactly this. No one new the answer. So thank you for confirming what I already suspected works.
Reduced engine pumping losses - surely.
@@ThePaulv12 also increases scavenging between intake and exhaust overlap
Making me think that if you had the unported head if would benefit from more exhaust duration and lift?
I don't know, maybe the cam timing events are close and improving flow within those events is key. The power stroke stops when the exhaust valve opens, just like the compression stroke actually starts when the intake closes.
@@jeffreydurham5342 yes
I did not see the 554. I did listen to the whole thing.
No 593-554-17=22
@@WeingartnerRacingwhen they don’t listen to your lecture professor.....
Why did you not run it on the dyno W/O the headers, you flow your ex ports W/O a pipe??????
You run your car without headers or manifolds? It would be pointless to dyno an engine without any type of exhaust.
@@jeffreydurham5342 So then it must be pointless to flow test the Ex port W/O a pipe, Right
This is simple and you know this Dave. The size of the pipe and the turn of the pipe change how much it flows. You can make nice straight huge pipes on the bench but that is not how the headers are.
Although long-time Tradition, Why are Exhaust ports flowed at Same Intake corrected pressure (28, 25" water, etc) when the exhaust gas is thousand degrees Hotter with practically Zero relative mass Inertia & no Wet flow dropout componets compared to the much Cooler dense wet Intake componets ?? .....Just seems logical to Test flow the Specific port (Intake or Exhaust) closest to its average Running Psi & temps.....Would dramatically increase the flow bench Complexity but possibly increase the Exhaust port Flow measurment to Actual running dyno Tracking differences relationship....
@@WeingartnerRacing Eric I would recommend you read page 87 of the superflow 750 manual.