Posted using the Full Custom H.A.M.B. App! I bought a never installed 20 year old offy manifold with two carbs on it. The carbs have stickers on them that say "factory remanufactured by holley" they are gm monojet carbs with different numbers cast into the side of the bowl. One is 7040021 the other is 7029021. Anyone know the difference and why would someone put different carbs on a manifold like that. Also i need a linkage. Any advice on that? Anything i should do to these carbs before trying them?
SO, I guess there were a TON of variations of this carb made. (Or was that the model B) Wondering about the reliability and performance etc. Are these any better than the original rochester carbs that came on the car? Posted using the Full Custom H.A.M.B. App!
I run into this all the time where a "dual or triple" carb setup is made up of different model number carbs. 7040021 - 1970 GMC-Chevy truck 7029021 - 1969 Chevy truck Both are model R1-MV and look the same. I would check to make sure the jet, metering rod, power valve are the same (they should be as they were used on the same size engine) as far as them being Holley reman, Holley had a division that would rebuild carbs.
Linkage should be pretty simple. Anyone make one or is it just as cheap to buy one? Who sells a linkage for it? Posted using the Full Custom H.A.M.B. App!
Eckler's has linkage for Offy re-pops. (I have not tried it.) http://www.ecklersearlychevy.com/ch...take-manifold-dual-carburetors-1949-1954.html
Patricks in Arizona is a great stove bolt speed equipment dealer ..they sell the offy linkage as well ..you could probably make it because its straight linkage not progressive... also if you don't have a cam in your engine I do recommend a dual exhaust manifold ..I would strip one choke ***y out of one of the carbs and re jet those carbs so your not dumping fuel ...the guys at Patricks are very helpful so you might want to run that jetting question by them for your application ..i heard the rule of thumb with stovebolts is the engine can be bone stock and you can run twin carbs with a header or split exhaust and the carbs jetted down...3x1 set up your goin to go into the engine a bit and you must change cam..whack the head down to bump up the compression and or change pistons...when it comes to getting kits for your carbs..dont waste your time or money on a generic kit from napa or auto zone..they have condensed many variations of carbs into one kit..you will find alot of sub quality components including the accelerator pump in these 15 dollar kits..my advice is to go online to mikes carburetors or a decent vintage carb re-builder who will give you the specific kits to your carbs.. Posted using the Full Custom H.A.M.B. App!
Jake, PM'ed you also. How much? Fuel line fittings included? Posted using the Full Custom H.A.M.B. App!
So I want to bump this up to ask peoples opinions of the carbs that I have. What difference would there be in engine performance, reliability, fuel economy etc between the monojets and, say, a pair of the carter webers from Langdons? All other things being the same of course. The engine is of unknown internal make up. there is an 848 head on it and it will have fenton headers and dual exhaust.
I go way back to working on trucks in a Chevrolet dealership from the era of those carbs which appear to be 1969 and 1970.......they are JUNK. I am much more comfortable with the older one barrels from approx. 1955 to 1961. To me, they are simpler, easier to modify and much smoother especially at idle and mid range. Just one old man's opinion
So tractor guy doesnt like them. Anyone else? They were designed for use on a similar or larger cubic inch 6 cyl so like someone said i need to make sure they are jetted down but what about reliability and performance. Has anyone ran two of these on a 235? I cant believe that i am breaking new automotive ground by trying this. Come on, share your experience with me.
I believe you will get better gas mileage with the Langdons Carter/Weber set up. Every one that I know really like the driveablity of the progressive two barrel carburetors. I gave up on the twin Rochester's on my 235 and went with a Clifford four barrel manifold with a Holley 390 CFM four barrel Carburetor.
Thanks James! That's the kind of stuff I was fishing for. I have read some people disparage the carter webers after switching to them as it seems that they lost some power and I recall reading specifically about hill climbing power and long grades at freeway speeds suddenly challenging their car after switching. That doesn't mean that they didn't disrupt something during the carb switch over that is causing the power loss though. Thanks!
The Carter Weber set up from Langdon's is superb! I did have a problem at first with low power as mentioned above, but Tom Langdon discovered my set were missing a critical breather hole punched in two places in the CW's. There is slightly less power at wide-open-throttle than with my original dual Rochesters, but still scads of p***ing and hill-climbing power over a single carb setup. The CW's give really smooth idling and low- to mid-speed running, far better than the Rochester setup. And NO leaking gas !
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