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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


Last edited by Big Bear; 06-10-2024 at 10:29 PM.
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Old 06-10-2024, 10:04 PM
74Grandville 74Grandville is offline
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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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Last edited by 74Grandville; 06-10-2024 at 10:19 PM.
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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 Yesterday, 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 Yesterday, 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 Yesterday, 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 Yesterday, 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 Yesterday, 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 Yesterday, 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 Today, 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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