Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum The fastest message board... ever.
Corvair Center 
Pages: Previous12
Current Page: 2 of 2
Re: Educate me on Four Barrel Carbs.
Posted by: goatsnvairs ()
Date: September 24, 2020 03:09PM

I have a JET stage 2 Quadrajet on my GTO, Believe the secondaries are mechanical. Available in 750 and 850cfm.

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: Wagon Master ()
Date: September 24, 2020 04:55PM

Yes your secondaries are mechanical but the butterflies above them are velocity opened. Curing the BOOOOOOG.

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: vairmech ()
Date: September 25, 2020 05:10AM

OK, let me answer a few different points here.

The Edlbrock is a Carter AFB knock-off. OK think Corvair Carter turbo carb and what a piece of crap it is. That is my opinion of most Carter carbs. Yes I have had a Carter AFB on a Corvair!

The Holley 390 works but it really needs to be set up correctly to work well on a Corvair. It takes time and a little knowledge to get it correct for the least amount of bog. I am not a fan of the vacuum secondaries but that is what everyone seems to get. Yes, I have driven the mechan ical secondaries Holly 390 on a street car!

The 500 cfm 2bbl is to large for street use. You will have driveability issues. I have tried to get the 500 cfm to work well on a buggy for normal driving and there was always an off idle bog and hesitation every throttle change. It worked well at full throttle! Yes, I have driven this on a buggy!

Now the Rochester 4 jet, That is the absolute best carb I have ever driven on a Corvair. The Corvair was an early with a PG even! That carb had no issues out of the box, no bog and instant acceleration. Yes I drove this for a while before I delivered it. The issue is try to find one now.

The Quadrajet, You want the one for the early pre-smog SBC. The big block uses the larger Quadrajet, there is even a larger primary in these. The SBC Quadrajet has very small primaries so there is very minimal low speed drivability. The lower secondary butterflies are mechanical but the upper plates are the venturi. Look at how they are bent. The Quadrajet needs to be set up correctly for the Corvair just like any other carb but in my estimation it is the best drivability carb on the Corvair that is available. OH, BTW The top butterflies WILL open up but not all the way, they are truly a simple variable venturi. Yes, I have driven AND raced with a Quadrajet on a Corvair. This is my overall preference for any aftermarket carb setup.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: Seth Emerson ()
Date: September 25, 2020 12:11PM

This is a 350 CFM Holley progressive 2-barrel(list 2305). Yeah, it looks, and mounts like a 4412 500 CFM 2-barrel, but it isn't one. This would make a great center mount carb for the Corvair - or even for a turbo. I wish I had one, but you could start looking for one!

Seth Emerson

Check my new Performance Corvair Web site [www.perfvair.com]

Attachments:
Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: steve c goodman ()
Date: September 25, 2020 12:30PM

Finding the Rochester 4jet from 3.5L BOP engines that I suggested and Ken says above worked well for him is difficult. There used to be a web forum similar to this that dealt with the Buick Special/Olds F-85 cars from 61-3. Google might find it for you now too.

I found a one several years ago for a customer here by going through that forum members. Maybe more out there.

I also installed one on a Corvair engine/912 Porsche conversion of mine in the 90s. Again I thought it worked very well and passed emissions etc too.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: dryenko ()
Date: September 25, 2020 12:44PM

I have a 4bbl Rochester carb with the square bore cast iron base
If anyone is desperate for one for their 57 chevy 283 SBC power pack engine.
Or a 140 Corvair center mount.
May even still have the manifold and the power pack heads marked on the end with a pyramid.
PM me if so.

Bob C aka Dryenko
Dobson, NC 27017

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: Frank DuVal ()
Date: September 25, 2020 03:02PM

Steve, I never heard of. 3.5 L Buick engine.grinning smiley

We only had cubic inches when I was growing up, couldn’t afford cubic centimeters. Those were for the VW and Porsche crowd. Ha!smileys with beer

Frank DuVal

Fredericksburg, VA

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: steve c goodman ()
Date: September 25, 2020 03:54PM

Frank DuVal Wrote:
-------------------------------------------------------
> Steve, I never heard of. 3.5 L Buick engine.grinning smiley
>
> We only had cubic inches when I was growing up, couldn’t afford cubic centimeters. Those were for the VW and Porsche crowd. Ha!smileys with beer

Steve sez: sorry Frank it is the 215ci BOP (Buick/Oldsmobile/Pontiac) aluminum V8 used in Buick Special/Olds F-85 and Pontiac from 1961-63.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: Richard ()
Date: September 25, 2020 05:43PM

Here is the back side of the 2305 Seth posted above. Phil, you should remember this carb as the one Dwight used to have on his race car.

Attachments:

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: chris ()
Date: September 25, 2020 07:50PM

Concerning the Quadrajet, I remember seeing that Demon had a Street Demon 625 (something like that). It had smaller primaries and seemed to be a combination of a Holley and Quadrajet. On paper/webpage it seemed like an okay fit for a Corvair, as I remember the primaries being slightly smaller than a Holley 390. Obviously the secondaries were larger but you get the idea.

'65 Monza 4 door
4 speed
110hp
Gardner, KS

Heart of America Corvair Owners Association

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: LesH ()
Date: September 26, 2020 08:19AM

Pontiac had their overhead cam Sprint 6 engine back in the mid 60s - it came with a Quadrajet - can't tell you if it's the same carb as the V8 QJ, but it's tuned for a 230/250 6 cyl.

Like this:
[www.ebay.com]

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: jamesolefjensen ()
Date: September 26, 2020 09:12AM

According to Doug Roe, author of "Rochester Carburetors" (available on Amazon, among others), there are only 2 Q-Jet "sizes"; a 700-ish CFM and an 800-ish CFM version. The difference is in the primary venturis (one smaller and one larger).

I say "-ish" because the CFM of the Q-jet can be increased slightly by grinding away a little tab stop on the secondary air valve (the flap over the secondaries) allowing it to open further. Obviously, this would not be advisable on a Corvair application.

The other way the CFM can be "tuned" is by adjusting the spring tension holding the air valve closed (more tension requires more airflow for a given air valve angle or opening). For a Corvair, this could be tightened up to improve throttle response and maybe even avoid over-carburation at WOT. Perhaps that's what John DeLorean did with his SOHC six-cylinder engine

The Q-jet on my Chevelle has fed a mellow 400, a wild 327, and a mild 350. The air valve spring adjustment is a very effective way to tune out the infamous Q-jet bog.

James
65 Corsa
SF Bay Area

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: LesH ()
Date: September 26, 2020 09:15AM

Having owned a Sprint 6, I can say that the secondary air valve spring tension is very important - needs quite a bit of tension to prevent the secondaries opening too early and bogging.

Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: JimBrandberg ()
Date: September 26, 2020 12:13PM

I love Inline-6 engine stuff, V-8s are everywhere.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Options: ReplyQuote
Re: Educate me on Four Barrel Carbs.
Posted by: vairmech ()
Date: September 26, 2020 04:08PM

jamesolefjensen Wrote:
-------------------------------------------------------
> Snip

> The other way the CFM can be "tuned" is by adjusting the spring tension holding the air valve closed (more tension requires more airflow for a given air valve angle or opening). For a Corvair, this could be tightened up to improve throttle response and maybe even avoid over-carburation at WOT. Perhaps that's what John DeLorean did with his SOHC six-cylinder engine

The air valve spring adjustment is a very effective way to tune out the infamous Q-jet bog.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

And that is why the Q-jet is the best option for the Corvair!

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

Options: ReplyQuote
Pages: Previous12
Current Page: 2 of 2


Sorry, only registered users may post in this forum.
This forum powered by Phorum.