Technical The Old Days of Dual 4's

I cannot imagine why anyone would do this!

 

@LOU WELLS I'm guessing your fill cap is vented? I wouldn't mind running breathers on mine, if I could find some old MT or especially some KB ones. But I bet I end up running a tube from the carb like you did, just to keep from cutting on an old set of Corvette or Cal Custom valve covers.

 

'63 or '64 Corvette ran a set up like that with a Horizontal PCV valve inline to carb from the factory. Their fill cap was not vented but can't remember where the air inlet was from. If you have the rite block you can run a catch can under manifold than a PCV & grommet from hole next to dizzy. I know I need pics it would explain it better! I will be doing something like that with my tunnel ram & Vet covers.

 

a couple of Edelbrock 500cfm performer's on a stroked 409, regularly driven, totally streetable at 10mpg

 

They were vented at the road draft tube at the back of the block.
I ordered a corvette kit from Eklers, the pcv that screwed into the oil fill tube was backwards flowing for what was needed, so be careful what you buy if you go for something like that.
I ended up just going back to a vented oil fill

 

Also if you notice on my first post those particular Carters have the fuel inlet on the driver's side, while my other Carters are passenger side, so be aware of things like that too when carb shopping.

 

Dual Quads look great on everything. WCFB’s are great carburetors. Air cleaners are Harley Davidson 90’s Evo on Charlie Prices air horn bases; PVC valve, V100, is between the carbs and horizontal.

 

If you run a PCV valve at the fill tube, you need one for a 66-7 Vette. The other one's were designed to screw into the back of the carb.

 

My wife ran 2 500cfm 2bbls on a 2x4 manifold with machined adaptors.... Worked great, although the mill was pretty pumped up !! Ak Miller used 4 Strombergs on a Weiand 2x4 on the El Caballo..

 

WCFB's would be the way to go; IF you can find a pair of the right ones. I had a pair on a 331 Cad for years; it ran ok for a pair of humped-up mixed parts carbs. I could probably rebuild one of them but the other carb needs a new main body and the correct one is tough to find. Getting closer to needing them and will probably have to get a pair of AVS-2's to get it on the road.

 

Yeah, Why?

 

Dave Schnieder of Schneider Racing Cams told my buddy to put 2 - 500 cfm Holley 2 barrels on his tunnel-rammed 327, and it worked bitchin'. Dave's FI Corvette road racer also left an indelible impression on me...

 

Here's my roadster...Mark gets upset when I show my other 2x4 intake

 

Or Z-28- or Chevelle/Nova L-79.

 

Jeff I actually bought them here in the classifieds from somebody, Knight Prowlers sold them (exact same ones) but I'm not sure if they are still in business or not.

 

Affirmative!

 

It was sold as a kit, should've been the correct one, the first time I screwed it in and tried to tighten it, it snapped the screw in bung right off the tube.
I had to weld that stupid thing back on, should've been my first indication that it wasn't the quality piece I thought I was getting, you'd think going directly to the corvette vendor you'd get the right stuff.

 

You'd think so! Seem's like we the consumer are the only one's that give a Damn about shit being right. The vendor just want's a quick sale...

 

If you use a Carter with the auxiliary air valve, this is not necessary, as the carburetor itself will block the secondary side, unless the engine asks for it.

GM used 750 CFM carbs on a lot of 6 cylinder engines.

Jon

 

Then will you have quad quads?

 

I've been scouring the old web for a set Jeff. Nothing looks right.

 

This is a setup I’ve been waiting to get back to work on. 93% sure I can make it work, which makes me happy. Been on my brain for a long time.

 

From experience, if one wants to add a PCV to early 2x4 carbs and intakes, plan on having a direct reading O2 sensor at hand. It's almost impossible to get the idle air-fuel ratio right by ear, since the PCV is a controlled air leak beneath the butterflies. Sometimes, there's sufficient adjustment in the carb idle circuit, sometimes, there's not.

Most early 4-bbls have a secondary idle circuit and the OEM 2x4 carbs closed that off, as having eight idle circuits was too much and very wasteful of fuel on decelleration.

Cadillac posted a Service Letter to dealer service departments detailing how to set up and tune the then-new 2x4 setups. It's still the bible today.

jack vines

 

^^^^^^ This has always worked for me. There is only an idle circuit on the front barrels on early WCFB’s. I idle on both and run on the rear carburetor. The exhaust is always clean along with the factory tips that are thru the bumper. You will notice at idle both carbs are very close to the same air flow. After 5 years they are still the same.

 

I have dual quads on an Edelbrock C26 like the OP posted. Two new-ish Edelbrock AVS2 500 cfm, rear is electric choke, manual choke on the front. Both needed some work out of the box to run right, along with some adjustments to the ignition system. Engine is a Chevy 350 ci, 290 hp crate engine. The idea that dual quads have to get poor fuel milage is a fallacy. The last 250 mile trip I took with this car I averaged 21 mpg.

 

I picked this up to get a carburetor for another project car, the front is a 500 cfm that looks to have never been used, the "other" carburetor is a "junk" parts carburetor. It was an impulse buy, something I've dreamed about for almost sixty years, not sure what I will put it on.