Quadrajet versus Holley spreadbore
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Quadrajet versus Holley spreadbore
I have a Holley spreadbore (650CFM, double pumper, mechanical secondaries) on my 383. Reliabilty of this carb has been marginal, including fuel leaks, poor idle, choke inop etc. I rebuilt it last fall and it ran very well for about 50 miles, then the idle speed dropped off, started running rich at idle again etc. Its getting frustrating. I also have the original Q-jet, which my local carb builder says he can modify at low cost to give better performance that the Holley. But, my engine builder says the spread bore gave much better power than a similiar Q-jet on the dyno, so, stick with the Holley. I want a reliable driver, but I want all the horsepower too.
Opinions?
Opinions?
Drifting
Joined: Jul 2001
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Re: Quadrajet versus Holley spreadbore (Lee)
Lee the extra 100 cfm that the Qjet has will do you a world of good with the motor you have.Throttle response can be excellent as well if the guy really knows his stuff.I think you will pick up gas milaege and MPH in the 1/4 mile with the Qjet over the 6210 you have.
Just don't adapt the Qjet to a squarebore intake manifold with those thick spacer/adapters.But if I remember correctly you have a spreadbore manifold.
Just don't adapt the Qjet to a squarebore intake manifold with those thick spacer/adapters.But if I remember correctly you have a spreadbore manifold.
Melting Slicks
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From: Union Ontario
Re: Quadrajet versus Holley spreadbore (mountainmotor)
Find Lars on the forum, he'll email you a tuning manual for the Quadrajet, then you can tune it yourself.
I have an 800CFM spreadbore holley on my 350..... yeah I know its too big. and have tuned and put the original Quad that I tuned up on it. The quadrajet has a good low and mid-range but loses out to the holley on top end.....but only by a bit, Which I could work on the secondaries more and get them working better.
I think the Quadrajet is a better all around Carb, better low end throttle response, better mileage.
I have an 800CFM spreadbore holley on my 350..... yeah I know its too big. and have tuned and put the original Quad that I tuned up on it. The quadrajet has a good low and mid-range but loses out to the holley on top end.....but only by a bit, Which I could work on the secondaries more and get them working better.
I think the Quadrajet is a better all around Carb, better low end throttle response, better mileage.
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Re: Quadrajet versus Holley spreadbore (Lee)
Lee, Check out this link over in C-3, I think it will answer some of your questions.
http://forums.corvetteforum.com/zerothread?id=233837
http://forums.corvetteforum.com/zerothread?id=233837
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Re: Quadrajet versus Holley spreadbore (Lee)
Love the Q-jets!! Some people laugh at them, usually not laughing when we compare time slips:bb . Tweaking a little at a time is the key.
Very tunable, and the small primarys are what help TR @ low end.
I have a 4010 on my 68' Camaro with very good luck. 750 cfm, Vac. Sec.
Lots of good books out there on Holley/Q-jet tuning. Each engine is different!
Steve
Very tunable, and the small primarys are what help TR @ low end.
I have a 4010 on my 68' Camaro with very good luck. 750 cfm, Vac. Sec.
Lots of good books out there on Holley/Q-jet tuning. Each engine is different!
Steve
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Re: Quadrajet versus Holley spreadbore (ALLTHROTTLE&NOBOTTLE)
Thanks for the input guys. I will spend the money to get the Q-jet set up right. Final decision was last night when I fired up the car to set the timing and spewed fuel out of the back bowl gasket on the holley again....Think I 'll use it as a pencil holder. (this is an old spreadbore designed for a 70-71 olds replacement, time it was retired)
Lee
Lee
