Quadrajet VS Edelbrock 76 D100 318
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- Опубліковано 28 вер 2024
- My friend recently had an overflow issue with his Quadrajet so he temporarily threw a good used Edelbrock on it to get around until we could fix the Qjet.
Thanks to the mechanical secondaries on the Edelbrock this has resulted in some pretty poor gas mileage and performance so I thought I'd take this chance to show some of the difference between mechanical and vaccuum secondaries on a heavy or less powerful vehicle. In some cases less is more and that is certainly the case here when comparing how much CFM a small engine sees at initial wide open throttle.
This is not an attack on Edelbrock carbs by any means, mechanical secondaries work just fine on engine that can handle the CFM and Edelbrocks excellent engineering can be seen through how well this Edelbrock intake works with this Quadrajet carb that is more appropriately sized for this engine.
Honestly this is more about mechanical secondary VS vaccuum secondary than Qjet VS Edelbrock.
My friend recently had an overflow issue with his Quadrajet so he temporarily threw a good used Edelbrock on it to get around until we could fix the Qjet.
Thanks to the mechanical secondaries on the Edelbrock this has resulted in some pretty poor gas mileage and performance so I thought I'd take this chance to show some of the difference between mechanical and vaccuum secondaries on a heavy or less powerful vehicle.
In some cases less is more and that is certainly the case here when comparing how much CFM a small engine sees at initial wide open throttle.
This is not an attack on Edelbrock carbs by any means, mechanical secondaries work just fine on engine that can handle the CFM and Edelbrocks excellent engineering can be seen through how well this Edelbrock intake works with this Quadrajet carb that is more appropriately sized for this engine. Honestly this is more about mechanical secondary VS vaccuum secondary than Qjet VS Edelbrock.
Yes sir I saw that one coming. I once tested a Q-jet vs. an Edelbrock vs. an old Holley 650 vacuum secondary spreadbore. Unfortunately I couldn't get the old Holley to run properly, but the Q-jet beat the Edelbrock in the 1/4 mile by three tenths of a second and 3 miles per hour N/A. Car weighed 3300lbs with a 3.73 posi and a TH350. I ran the same Q-jet on top of the 144 but was having issues with detonation. Instead of going through the trouble of tuning it I just slapped a big Holley on top and that fixed everything, that thing ran like it had electronic fuel injection. I did lose a HUGE amount of bottom end torque that I had with the Q-jet though. If you know how to modify and tune them they're tough to beat.
@@toefield251 Sounds like you've been having a lot of fun with that Camaro! It's really cool of you to save/remember the data too. I saw you trying to get the blower to run with the Qjet on top in the vid and I was impressed with how the blown motor was pulling the secondaries open in neutral when you would rev it. The secondaries are not supposed to open in neutral like that which shows that motor has some serious power.
@@Impactjunky Actually that carb test I did back in 1998. The blower video was made in 2001 before UA-cam even existed! I took that car off the road years ago when they passed some seriously harsh street racing laws out here. Didn't want to risk it. But I still have it and it still runs. The way that truck lights 'em up right out the gate with the Q-jet shows how much bottom end those small primarys and "vacuum secondarys" give you, that's why I mentioned how much torque I lost with the Holley compared to the Q-jet. It would be interesting to see you do a Holley vacuum secondary vs. Holley mechanical secondary vs. Q-jet test on that 318.
I have an 88 Ram 318 that I swapped over to an Edelbrock 1406 and Speedmaster dual plane midrise intake. I thought about buying a Q-Jet but I didn’t want to take the gamble, as no new Q-Jets are built and I have no experience with carburators.
I think the Edelbrock liked the slightly higher compression and power of the stock roller cam and stock swirl port heads, because in comparison to the TBI, throttle response and performance seemed to double. I did slightly lose some low end but the mid-range and high range gains felt astronomical in comparison. It’ll now squeal the tires as well, which is surprising for a bone stock and worn out 318.
I find it odd that performance and gas mileage dropped. My best guess is that Q-Jets really were meant for lower compression and lower revving engines, and also meant for a dual plane intake.
Sounds like a cool truck, good luck with the project! Qjets were actually a state of the art high performance carburetor in their day and came on lots of brutally powerful high compression engines. My 71 Cadillac with the 7.7 liter 472 had 500 FT pounds of torque stock which is just a few foot pounds behind the highest torque production car ever made and it came with a Qjet. Same thing with the Pontiac Ram Air 455 which was the highest torque production car for over 30 years before the series 2 Viper came out. I actually already tried to tell you exactly why the Edelbrock was worse in the writing in the video. To further explain it when you floor the Edelbrock you get all 4 barrels and all 600 CFM at once, and a mild engine in a heavy truck like this can't use all that air right off idle. Its too much air and it bogs your low end intake air-speed which kills your torque.
The Quadrajet is a split or vacuum secondary carb and only runs on the small 200 CFM primaries when you are cruising at low RPM. The rest of the full 750 CFM only comes in at wide open throttle at a later RPM when engine intake vacuum actually needs it. This design is superior for eliminating low RPM bog and maximizing top end power and fuel economy since you get the best of both a smaller and a larger carb. Having a Qjet is like having two carbs, a small one for regular driving and a large one waiting in reserve for anything above half throttle.
@jordantomblin2302 Also I forgot to mention that if you get a chance to try a Holley 600 vacuum secondary carb then your truck will likely love it. It has vacuum operated secondaries like A Q jet but its way easier to work on and tune. A lot of people don't like the Qjet because it is rather complicated and has a lot of moving parts but a Holley is super simple and provides great performance and mileage. Edelbrock also makes some small vacuum secondary carbs that should run pretty good but I have no personal experience with them yet.
I like this truck, would be cool to see it doing block-long burnouts with a built magnum or 440!
@East Bay Hounds Yeah that would be awesome! When it had the Qjet it was unbelievably quick for a 4000 pound long bed pickup with a low compression small block and an automatic. Unfortunately the only video we have of the truck running at 100% with the Qjet is that night time burnout vid I keep re using. With the Qjet hooked up and running right you can be cruising down the road and floor it and it will open the secondaries and make that
badass bu-WAAAHHHH sound and pull surprisingly hard.
The truck came from the factory with an open 3.55 axle so with his current setup the top of 1st gear is about 40 MPH and the top of second gear is about 65 MPH and the top of third is about 107 MPH. When everything was working right I think it was possibly faster 0-60 than the Satellite was with the 273 and 3.55 gear.
Qjets are just simply better carbs. Little more complicated but way way better that small primaries and large secondaries
The heck is this? 180whp? Nothing but slow garbage on your page. Can’t even break the tires loose. My 1.8 liter Honda makes more power.
@J&D Racing ADD got your head swimming too much to watch the whole vid? Either way the sad thing is your massively modded turd might make a couple more HP than this mostly stock tired 76 model engine but you still make less torque. Your little baby 1.8 would overheat and die trying to move this 4000 pound truck.
That truck sounds good
@B5 BEAST My friend will appreciate the compliment, this is his first project vehicle and he's loving it!
The 2nd Qjet clip sounds like a whole different animal 🙉 🎶
@MrJohn613 Budget Builds Yeah the difference is crazy, the truck has no low end whatsoever with the mechanical secondary Edelbrock. Honestly it barely runs better than the stock two barrel. The Qjet really does it justice though. A smaller Holley vacuum secondary should run a lot like the Qjet too but we've yet to test one on it.
Qjet for the win performance and economy. Honesty to me the only thing better is a holley efi system.
@Efurd Garage When comparing the same amount of CFM those EFI setups usually make less horsepower on a dyno than a carb of the same size and I know for a fact they can't compete with the Qjet and vacuum Holleys insane bottom end. I've never seen an EFI system that runs on 200 CFM until it needs more. Modern throttle bodies give you all the CFM at once which is exactly why Edelbrocks suck. Exact same problem just with a computer attached to it.