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Old 06-10-2024, 09:53 PM
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Default Q-Jet on Olds 455 surprizes Nicks Garage

Dynoing the Olds 455 the first impression Holley carb was the way to go until they bolted on the original Q-jet. https://youtu.be/5Iu0eJUjEAQ


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Old 06-10-2024, 10:04 PM
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This is the correct link. https://youtu.be/5Iu0eJUjEAQ?si=wa4fRXwDZZBnO1cU

the old square bore on a spread bore intake senario too. that can't be ideal for the Holley.

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Old 06-10-2024, 11:08 PM
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loved the guys reaction!! the idle circuit wasn't correct. so I'm thinking it could have been dialed in a bit more for more power. love q-jets !!

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Old 06-11-2024, 07:31 AM
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Good thing I didn't give them a 1976 or later Olds Q-jet for the testing or they would have been dialing 911 for old Tony!

The unit they used was a 1970-74 style Olds Q-jet. They aren't that great anyplace and I avoid them for high performance work. Probably OK on the dyno at that power level but Olds (and Cadillac) continued to use the poorly located hinge pin and large float from the 1965-68 designs.

I'd add here that it still has an advantage in that scenario as a spread bore carb doesn't require an adapter and lines up perfectly with the center of the plenum areas vs the square flange carb they were testing. I've been asked more times than I can count to do that type of testing, dyno and at the track. I very quickly learned to keep a box of diapers close by so I could hand them out when the old/ugly Q-jet whipped up on the Holley and Holley cloned stuff!.......

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Old 06-11-2024, 08:36 AM
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In my 63 GP I installed a 65 421 years ago with carter afb. Tried edelbrock aluminum intake with square bore small Holley. Then tried holley spread bore with iron qjet intake rejetted both rejetted. Then I acquired 70 455 ho qjet. I tried it. Cant remember if I changed jetting. It was better everywhere,performance mileage, response on the street.


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Old 06-16-2024, 10:32 PM
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Quote:
Originally Posted by Cliff R View Post
Good thing I didn't give them a 1976 or later Olds Q-jet for the testing or they would have been dialing 911 for old Tony!

The unit they used was a 1970-74 style Olds Q-jet. They aren't that great anyplace and I avoid them for high performance work. Probably OK on the dyno at that power level but Olds (and Cadillac) continued to use the poorly located hinge pin and large float from the 1965-68 designs.

I'd add here that it still has an advantage in that scenario as a spread bore carb doesn't require an adapter and lines up perfectly with the center of the plenum areas vs the square flange carb they were testing. I've been asked more times than I can count to do that type of testing, dyno and at the track. I very quickly learned to keep a box of diapers close by so I could hand them out when the old/ugly Q-jet whipped up on the Holley and Holley cloned stuff!.......
Cliff, you’ll love this; ran across a post from a guy who swears you can’t make 450hp with a Q-jet without major internal modifications. I pointed him toward Randi Lyn Butner’s ‘67 Firebird that has turned 10.29s against an 11.00 index in D/SA. Using the Wallace Racing calculators that indicates 578 horsepower with a nearly STOCK Q-jet on a Stock class legal 400. He didn’t have much to say after that…

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Old 06-11-2024, 08:42 AM
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When one looks at all the cars in NHRA classes that have been forced to use them and the times that those cars turn it becomes very clear that those who use a blanket statement that they suck just don’t know about them because they have spent their entire carburetor learning curve with Holley’s.

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Old 06-11-2024, 12:31 PM
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My 70 qjet (reworked by cliff) made around 3-4 hp more on the dyno than shops 850 Holley DP.

On nicks olds 455 dyno engine I was more concerned with the oil pressure dropping through the run but it made good power for what it was.

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Old 06-11-2024, 01:51 PM
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You could tell no one in that room could even tell what size it was. I was kind of shocked at the oil psi dropping as mentioned plus 19 psi at an idle on a new engine? Yikes.

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Old 06-11-2024, 04:00 PM
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To me working on all kinds of engines on the dyno, a Holley carb is like a anvil and a mini-sledge. It will get the job done and can deal with huge changes very quickly and easily to get an engine in the ball park. A Quadrajet is like a fine surgical instrument. If your willing to put in the time and effort, they are just fantastic and do everything well. No matter what I do tuning wise, I can't match the economy of a Q-Jet with any Holley I have ever used. Pontiacs just seem to really love Q-jets.

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Old 06-12-2024, 07:45 PM
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Right now, I'm running a 69 cast iron manifold w/ a matching Q-jet from a 428. Rebuilt with one of Cliff's kits & parts. By far, the best street combo to date.

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Old 06-13-2024, 12:24 AM
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I wish they would have stuck a sock in Dr. Olsmobile's big yapper, and made him sit in the corner. He had nothing worth contributing to the dyno session. The big guy, named Tom, had they right ideas of what to try next.
I'm glad Cliff got to see that. I was wondering about that specific Q-Jet...
The engine owner Tony mentioned that 800 cfm Olds carbs were rare???
Are not nearly all Q-Jets after 1976, 800 cfm units? Cliff?
I don't think they mentioned who built the carb.

Nick does all this engine building, but doesn't seem to want to tear into any carb that's not a Holley. He worked at a GM dealer, way back.

Nick says all his dyno carbs are new carbs. It was nice to see a 53 year old carb stand in there!!!

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Old 06-13-2024, 12:24 AM
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I wish they would have stuck a sock in Dr. Olsmobile's big yapper, and made him sit in the corner. He had nothing worth contributing to the dyno session. The big guy, named Tom, had they right ideas of what to try next.
I'm glad Cliff got to see that. I was wondering about that specific Q-Jet...
The engine owner Tony mentioned that 800 cfm Olds carbs were rare???
Are not nearly all Q-Jets after 1976, 800 cfm units? Cliff?
I don't think they mentioned who built the carb.

Nick does all this engine building, but doesn't seem to want to tear into any carb that's not a Holley. He worked at a GM dealer, way back.

Nick says all his dyno carbs are new carbs. It was nice to see a 53 year old carb stand in there!!!

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Old 06-13-2024, 05:08 AM
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The only big cfm early carburetors are the 1971 HO 455 units (and the 1971 400 4speed), 1971-74 Buick 455's and 1973-74 Super Duty.

All the non CCC front inlet carbs from 1975-up will be the larger castings and most of the side inlet as well provided they are the later hot-air or electric choke models.

The 1971 455 HO carbs flow 827cfm, the 71-74 Buick 455's and Pontiac Super Duty Q-jets are 850cfm.

All of the large casting models are typically dubbed "800" cfm but the flow numbers on them are all over the map as the factory limited the full open angle of the secondaries for the application. A good example of this are the Pontiac 301 Q-jets. The stop on them is so long that the air flaps barely open. About 5 seconds with a grinder to shorten up the stop and they are 850cfm. My bood describes the optimum opening angle for the secondary air flaps for maximum CFM without going too far with them.

I used a 1977 Pontiac carb on five different engines that powered my Ventura over a span of nearly 40 years. It's been on the dyno countless times and thousands of track runs with PLENTY of back to back testing against other types of carburetors. Not one single time, dyno or at the track has anything outran it. I'll also add that a grinder or sanding roll has never touched it, so it's a completely "stock" unit with a little ground off the stop to get it to "850" cfm, and recalibrated exactly for what it was being used on.

The only times to date it was "outran" was at the track during one of the HPP "Shootouts". I replaced both the intake and carburetor with a Tomohawk, 1" spacer the 4781-2 Holley DP carb. For all testing that day that combo was worth a solid 2mph on top end over all other carbs, intakes and spacers tested. Even so the 1977 Pontiac Q-jet on a factory cast iron intake with no spacer ran the quickest ET that day, besting out the big intake and Holley by .02-.03 seconds. Another example clearly showing how big intakes and carbs do make more upper mid-range and top end power, but more average power gets the car there quicker as it leaves harder (improved 60' times) and more power in the loaded RPM range.......FWIW.....

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Old 06-13-2024, 05:08 AM
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The only big cfm early carburetors are the 1971 HO 455 units (and the 1971 400 4speed), 1971-74 Buick 455's and 1973-74 Super Duty.

All the non CCC front inlet carbs from 1975-up will be the larger castings and most of the side inlet as well provided they are the later hot-air or electric choke models.

The 1971 455 HO carbs flow 827cfm, the 71-74 Buick 455's and Pontiac Super Duty Q-jets are 850cfm.

All of the large casting models are typically dubbed "800" cfm but the flow numbers on them are all over the map as the factory limited the full open angle of the secondaries for the application. A good example of this are the Pontiac 301 Q-jets. The stop on them is so long that the air flaps barely open. About 5 seconds with a grinder to shorten up the stop and they are 850cfm. My book describes the optimum opening angle for the secondary air flaps for maximum CFM without going too far with them.

I used a 1977 Pontiac carb on five different engines that powered my Ventura over a span of nearly 40 years. It's been on the dyno countless times and thousands of track runs with PLENTY of back to back testing against other types of carburetors. Not one single time, dyno or at the track has anything outran it. I'll also add that a grinder or sanding roll has never touched it, so it's a completely "stock" unit with a little ground off the stop to get it to "850" cfm, and recalibrated exactly for what it was being used on.

The only times to date it was "outran" was at the track during one of the HPP "Shootouts". I replaced both the intake and carburetor with a Tomohawk, 1" spacer the 4781-2 Holley DP carb. For all testing that day that combo was worth a solid 2mph on top end over all other carbs, intakes and spacers tested. Even so the 1977 Pontiac Q-jet on a factory cast iron intake with no spacer ran the quickest ET that day, besting out the big intake and Holley by .02-.03 seconds. Another example clearly showing how big intakes and carbs do make more upper mid-range and top end power, but more average power gets the car there quicker as it leaves harder (improved 60' times) and more power in the loaded RPM range.......FWIW.....

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Old 06-13-2024, 05:21 AM
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While we are on the subject of Q-jets and CFM ratings, performance potential, etc, consider this. Below is a link to Brent Flynn's Firebird at the track. It's a pretty "basic" engine build, 408cid, upgraded rods, pistons, and ported early "D" port cast iron heads. It's higher compression and uses a Comp flat solid 300B camshaft. On top of the intake sits a 1969 Q-jet, the smaller casting, set up for E-85. This Q-jet has the better hinge pin location and smaller float but the same size casting as the Olds Q-jet Nick was impressed with. It would have made more power on the dyno simply due to the superior design and improved fuel control. I've dyno and track testing both variety back to back enough times to know that I would never use one of the early units with the short hinge pin and large float unless class rules mandated it.

https://www.facebook.com/brentwillia...21130332784502

Brents car is also a prime example of the performance potential of the Pontiac 400's. No roller cam, no stroker crank, no CNC ported aluminum heads, no big intake manifold or big CFM aftermarket carburetor. Just a well thought out combination to end up with a strong running Pontiac without a lot of aftermarket or exotic parts......

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Old 06-16-2024, 09:19 AM
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As Cliff mentioned, the adapter could have held back the Holley slightly; air fuel mixture like a straight line direction.

The guys just didn't want to give up on the Holley, even confronted with the numbers.

But honestly, an 850 Holley probably does not flow any more or possibly even as much as a 750 Q-Jet WHEN the Holley is sitting on top of an adapter.

Now the real question is: what would have the numbers been with a 850 TQ or a 1000 TQ, both of which would require no adapter? Or is the 750 CFM of the Q-Jet actually enough for the 455 Olds?

Jon

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Old 06-16-2024, 10:24 AM
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I have run Qjets I've taken the time to dial in and Holley/Demons. Like Mike said way easier to start dialing in a Holley/Demon.

As far as the adapter debate-yes theoretically the flow probably is not as great with a square bore but I did an at the track swap years ago on my first E head motor. I kept the HO intake so I could use my Shaker until I could find another Shaker base to modify for Holley/Demon clearance. I had run on my RAIV heads on a 455 then a 400 and the 73 SD SR replacement I had Brad Urban tweaked, since then tweaked by Cliff but not run since that. 259/262 @ 0.050 solid roller and ported E heads so maybe a little more air flow than ideal for the HO. At the track swapped on an out of the box Demon 850 DP WITH the adapter picked up 0.3 seconds at the track! So if it was hurting air flow the motor sure did not know it. Later swapping a Torker II -not same day-it picked up a bunch more and idled even better with the single plane and the Demon. I had blended the adapter some to smooth out any transitions and it was the open one not the 4 hole like the Edelbrock.
https://www.edelbrock.com/quadrajet-...-kit-2697.html
https://www.amazon.com/Trans-Dapt-20.../dp/B000CQ47QK
I have noticed this new edelbrock open does slightly move the carb centers between square bore and spread bore. the GM Racing SBC iron intake for both for classes that require a cast iron intake does the same.
https://www.edelbrock.com/competitio...fold-2693.html

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