Rebuilding a 61 Chevy 261, 848 head, mild street cam, Fenton headers. Will be matched up to a T5. ******, and 3.70 rear. I presently own two Holley 94 carbs, AND have two adapters to mount them to a 1-barrel manifold. Would using the adapters to mount the 94's to an Offy or Fenton dual carb intake be overkill? The CFM of the Holleys is about 150, correct?
I think they would be perfect on your setup. I run two '94s on a flathead ford with a smaller displacement than your engine and they work very well. They are supposed to flow 150 cfm so the pair would be about 300. Air flow calculations show that 300cfm is a good size for engines around 250 cu. inches with mild modifications.
I'm running 2 94's on an Edmunds manifold on a hot 216, and it pulls my 4-door Fleetline around without issues.
I have a 261 with 2 edlebrock 94 with a Howard cam. I did buy a hei with external coil from Langdon stovebolt. It runs great!!!! Took it on the power tour and I have around 15k miles on it. Never had a problem and it gets around 20-22 mpg if that means anything
Mileage that good? Impressive. This 261 is going in a 49 Fleetlune, and was thinking of using it as a daily driver. I read somehwere of "splitting" the throttle shaft on a two-barrel, so the throttle plates can work independently, and can be set up so that one side acts as a primary, and the other works as a secondary... how complicated/involved is this mod?
According to a post by "Carb King" you don't just add up the CFM, you have a 'loss" due to inefficientcy caused by linkage & other things, he was saying you'd probably get no more than 80% of the total(drops with number of carbs used, ect). Wouldn't look "traditional" but Carbs used on Vegas & Pintos in the 70s work this way.
Van, I have an extra Offy intake if you are looking for one. Bought it for my 261 but ended up finding a Tattersfield.
The old Harper 3x2 setups ran the split throttle shafts. I sank some coin in an initial attempt on my 216, but abandoned it as unnecessary. Too complicated, too expensive, and nothing to be gained. The car is quite well mannered with straight linkage. (Jahn's pop-up pistons, McGurk dual pattern cam. headwork, etc.)
Patricks Chevrolet sells the adapters and carbs to put 2, Holley Weber progressive 2 barrels on your manifold. The carbs are not expensive, about $85 the last time I looked. This is the 2 barrel used on Vegas, Pintos, and about 50 million import cars. It is supposed to work real well on the street.
I think I will keep it simple, and jus use the 94's, with straight, non-progressive linkage (since I'm only using 2). Just wanted to make sure I wouldn't be over-doing it.
I think you're on the right track. I have heard you use two 216 carbs for a 235 and two 235 carbs on a 261.
If you decide to go the progressive 2 barrel route, Langdon does have Carter Weber progressive 2 barrels, (32DFT) that you can install, along with adapters, linkage etc. Those are on their website at www.langdonsstovebolt.com
Many of the Chevy "Stovebolt" forums, both here and others, seem to think that dual 2-barrels may be overdoing it on a 235/261 Chevy, due to the "poor breathing" of the head used on those engines. I really don't see that. The Flathead probably has much poorer flow, even with porting, than a 235 head, and have about the same displacement, yet rodders often have 2-3 97s or 94s, on their flatties and report they have good "every day" driveablity. I see that a couple of you posting here have used the same, even on a 216. Are these Stovebolt guys just being "Rochester snobs"?
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