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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: texas yenko dude ()
Date: November 07, 2009 04:23AM

I do have a Carter AFB 4200s if anyone needs one. Price is $40.00 including shipping. It has been on the shelf for a few years, but worked great when last ran.

Texas YENKO Dude
YS-070
YS-199
YS-320
Southeast of Disorder


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Re: De- Jetting????
Posted by: Scott V ()
Date: November 07, 2009 04:33AM

MattNall Wrote:
-------------------------------------------------------
> The only way to reduce CFM is to put
> restrictors [ chokes in Webers] in the Venturii.

different size chokes or restrictors in the venturii arent the only way to reduce cfm -

restrictor plate between the carb & the manifold.
restrictor plate on top of the carb.

-Scott V.

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Re: De- Jetting????
Posted by: MattNall ()
Date: November 07, 2009 04:53AM

Scott V Wrote:

> restrictor plate between the carb & the manifold.
> restrictor plate on top of the carb.
> -Scott V.
==============================================================

Smaller intake tubing..

Washers [ orifice] in the rubber connector hoses

Orifices in the manifold to head flages

Move to Higher elevation..

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Re: De- Jetting????
Posted by: RCSmith ()
Date: November 07, 2009 05:00AM

Dirty aircleaner !!!


smiling smiley

Ray C. Smith
'66 Corsa


Bergen County ,NJ

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: cnicol ()
Date: November 07, 2009 05:51AM

The whole idea with "right-sizing" the carburetor cfm-wise is to have an efficient carburetor operating in its design range meaning air flow through the carburetor is the right speed for efficient carburetor operation. Installing an oversized carburetor will result in airflow that's too slow and weak vacuum signals inside the carb. (Vacuum signals cause fuel to flow proportionate to air flow).

Changing the jets, manifold tubes, or restrictor plates will not change fact that the running cfm is below the carburetor's designed flow.

A 140 operating at WOT and 5200 rpm draws under 250 CFM, well under the maximum theoritical flow for four stock carburetors (about 450 CFM), about 1/2 the maximum flow rate of even the atypical small 500 CFM 4bbl.

IMO, if you want more power out of a Corvair engine you have to increase the airflow capability, yes, but the 140 carburetors are not the point of restriction; it's the camshaft, cylinder head, and engine displacement. If you want to start a thread on increasing engine power I'm sure you would have lots of interest.

FWIW, the magic of the Weber carburetor is in the intake design which allows the installation of a radical, power and airflow adding, camshaft without the usual compromise of weak, lumpy idle and weak bottom end torque. The Weber intake design features individual intake runners which isolate the cylinders. This design prevents "cross talk" in the intake and provides stable vacuum, idle quality, and bottom end performance even with camshaft that would have a poor idle and bottom end in a conventionally manifolded engine. The magic is in the intake more than the carburetor but then the carburetor is optimized for individual intakes so it's kinda special too.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
66 Red Monza 2dr 140/4 EFI 60k
61 Seamist Jade Rampside 140 PG
65 Cypress Green Monza 140/4 4dr
65 White 4-dr 110/AC/PG (parts)
64 GB -CrUnChEd (donor)


20 Tons of parts in boxes

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: RCSmith ()
Date: November 07, 2009 06:32AM

Craig ,

Nice explanation .

In reference to CFM of carburetors , would you know what pressure drop is used to rate the Rochester 1bbl HV and the various barreled Webers ??
Do I recall correctly that a 4 bbl CFM is rated at 1.5"Hg and a 2bbl at 3" ??

Ray C. Smith
'66 Corsa


Bergen County ,NJ

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: Darrin ()
Date: November 07, 2009 11:03AM

What about the Holley 390 CFM carb...I thought that was a common choice.

Darrin

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: 66ragcorsa ()
Date: November 07, 2009 02:56PM

Craig, thanks for all the info! That was great food for thought. I have the lower end stuff already in the engine, so if I could talk my wife into the weber setup we would be all set. The Isky 280 cam may have to be changed, but it is a start. Does that look like a decent buy on the intakes and carbs on Ebay - see link on bottom of first page?

Thanks!

Steve T
Michigan
1966 Corsa Convertible
Photobucket

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: SpyderMan ()
Date: November 07, 2009 03:35PM

Steve, is there a goal for for how much HP you want when done? There are a hand full of guys here running IDAs they would be the best to tell you if that setup is a fair price.

Sam Russell
Chapel Hill NC
1962 Monza Wagon
1964 Spyder coupe


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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: vairsnvettes ()
Date: November 07, 2009 03:55PM

I have a NIB Carter 390 AFB I bought thinking I would go with a 4bbl. I have decided to go EFI instead. PM if interested.

Mark
66 Corsa Coupe

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: slickcar ()
Date: November 16, 2009 03:21AM

does anyone have a picture of the modified afb 3858, and how do you know if you have one of those? I'm too lazy to check right now it is in the 20's outside, don't wanna go outside...lol

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: steve c goodman ()
Date: November 16, 2009 03:44AM

To add to the list of restrictions that Craig started above, the stock exhaust tube with the flat side to clear the oil return tube is very damning for free flowing heads.

To add my vote of carbs for centermounts: I used a Roch 4CG on the Porsche conversion from a 3.5L alum Buick. To guard against icing I used a hot air tube into the air cleaner, picks up hot air from the left side exhaust manifold.

Sincere regards, Steve

1962 spyder 3.0L turbo 1967 monza 110/4
1968 monza 110/4 1971 amante gt 110/4

Golden, Colo. CORSA/RMC/PPCC

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: 66ragcorsa ()
Date: November 16, 2009 12:23PM

Steve, do you have a picture of that setup? I was thinking about using angled exhaust tubes and headers with my setup and something different with the carbs. There is a lot of interesting chatter about EFI and that sounds interesting, but too $$ and the thought of hundreds of hours programing??? If I had a choice of a great running stock engine vs an okay EFI, I would take stock any day. GM spent a lot of $$ engineering these things and they run pretty good stock when they are done back to orig. design. Maybe I just leave it all alone?

Thanks

Steve T
Michigan
1966 Corsa Convertible
Photobucket

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: gabbagabbawill ()
Date: November 16, 2009 03:44PM

My guess is that most carb problems that folks are reporting are due to bad/ inadequate jetting on a non-stock carb. That said, TOO BIG of a carb can lead to loss of power in the lower RPM's. The way the motors on these cars are designed, I wouldn't want to lose any bottom end.

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: Bob Helt ()
Date: November 16, 2009 04:21PM

I'm coming in rather late to this discussion, but there is something that seems to be missing here. Craig gave an excellent description of carburetor CFMs but there is more to be said about the selection of a 4-BBL carb it seems.

Depending on the both carb and the engine, normal operation will only activate the primary section of a 4-BBl when engine demands are low such as low RPMs and cruise. It is only when engine demands are high that the secondary section of these carbs are activated. And to complicate matters, some carbs have their secs activated via vacuum and some by accel opening (i.e., mechanically).
That being said, one needs to discover just what the CFM capability is on each section of the carb. Small venturis on the primaries will give near stock performance for loads that do not activate the secs. So a carb like that will give excellent performance for normal driving, but if the pris are too large, then low speed performance may be worse than stock. Similarly, when and how the secs are activated will control high speed performance. If the secs are too small or activate late, or maybe don't ever activate if the engine vacuum isn't low engugh, high speed performance may be poor. In fact how will one ever know when and how the secs activate if vacuum operated, other than possibly by the seat of the pants feel? Likely, some carbs with vac activation, open the secs too soon and the drivers never know it and some actovate the secs too late, all due to a mis-match of the primaries to the engine. So it seems that mechanically activated secs would be better.

So bottom line IMO, one must select a 4-BBL not only by reported cfm, but also by the cfm for each, the primary section and sec section. And in addition by how and when the secs are activated.

Regards,
Bob Helt

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: firevair66 ()
Date: November 16, 2009 11:10PM

I have a NOS Edelbrock set up (still in original box and newspaper packing from 1972 . They reccomend the Holley #1849 , 550 cfm and supply the carb modification parts , primary jets , secondary plate and diaphram spring for that carb. They also replace the acell. pump cam and increase the squirt holes from .025 to .028 . tThey also increase the idle feed restriction by .005 and the primary valve restriction by .005.They also plug the secondary kill bleed hole. I also have a new IECO setup that reccomends the carter 650 cfm . It looks as though they didn't use small cfm carbs back in the day when these things were popular. I am running a 750 holley on one now that runs very nice , I haven't connected the secondaries yet as I need to make the linkage and see how far and when to bring them in. I feel the slower flow of the larger cfm carbs may help the iceing problem that some report. We will see.

John Shoemaker,Riegelsville,PA.
61 Rampside full custom show truck
65 Monza 110/4 vert driver
65 Full Custom Monza 140 Cp
66 Corsa FITCH SPRINT Documented ( in Process,recondition)
66 CorV8 350 "firevair"Custom Show




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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: Jim ()
Date: November 18, 2009 05:44PM

My parts may be in next weel to 10 Days and I will stuff this under the car.

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: Brad54 ()
Date: November 18, 2009 06:34PM

I'm totally new to Corvairs... just bought my wife a '61 Lakewood with '66 140/4-carb engine for her daily driver. Lots of little tuning things to do, but so far she loves it.

I'm about to have some induction system issues--we need the chokes to work, but a quick look showed the choke bodies were wire-tied to the carbs, so they need some work.

Rather than running a single 4bbl carb with very long runners, has anyone run a pair of 2bbl carbs on short runners, installing them over each bank of the engine?

Tuning would be easier than 4 carbs, and there's a much broader choice of 2bbl carbs out there, rather than finding/rebuilding 4 single-bbl carbs.

Thoughts?

-Brad

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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: firevair66 ()
Date: November 18, 2009 07:14PM

slickcar Wrote:
-------------------------------------------------------
> does anyone have a picture of the modified afb
> 3858, and how do you know if you have one of
> those? I'm too lazy to check right now it is in
> the 20's outside, don't wanna go outside...lol


The 3858 is very rare and if you do find one it will set you back BIG $$$$$$.
IECO used to use them on their 4 bbl setup and when they ran out switched to a modified 3310 , 750 cfm holley,

John Shoemaker,Riegelsville,PA.
61 Rampside full custom show truck
65 Monza 110/4 vert driver
65 Full Custom Monza 140 Cp
66 Corsa FITCH SPRINT Documented ( in Process,recondition)
66 CorV8 350 "firevair"Custom Show




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Re: Best 4 barrel Carb for a 4 -1 setup?
Posted by: Jim ()
Date: November 18, 2009 08:56PM

Today

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