The Stovebolt Site Forums The Shop Area The HiPo Shop Headers and Dual carbs on a 6 cyl

well, I was looking for info on what jetting to run in the 2 rochesters I'm putting on the new 261.
Now I hadn't heard of a Weber Carter carb...
This 261 isn't really a Hot Rod motor.
I just wanted it to move along when I want/need it to. Its already my daily driver with the dying 216 in it.

Specs of the 261:
+.060 pistons
254 delta Cam
hardened seats and stock sized valves.

I was planning on running dual Rochesters on an Offy manifols with the Fenton headers.
but now I'm wondering if there are better carbs to run.

Jeremy

Jeremy

I have an almost exact setup in a half ton. And what a blast it is! Get some taller rear gears and you'll go as fast as you want!

Just a suggestion......check out the Holley/Weber carbs offered at a bargain price from Tom Langdon (Stovebolt Engineering Co.) Think you'll find that a pair of H/Webers are better suited to the 261 than the C/Webers.

I've used the H/W's and the C/W's on my truck engines and can verify that they are a terrific replacement for the leak-prone Rochester. In addition, both the H/W and C/W eliminate all the other negative issues of the worn-out Rochesters and will allow you to really enjoy your truck.

Dave

Headers,why.This goes back to the old split manifold,just a little cutting and welding.Headers on a straight six do nothing more than give it a good sound.Dual carbs.????they look nice but thats about it.If you wanna up your performance install a forked 8,and go from there.

why? because he wants to I suppose. Headers give the same benefit to a straight six as to any other engine. Dual carburetors give the same benefit to a straight six as to any other engine. Of course you have to do modifications to be able to reap the benefits, just like any other engine. You can't just throw twin carburetors on a stock v-8 and expect it to work. Putting a v-8 in one of these truck is very effective, but it is so much the sheep mentality, any one can do that.

throw twin carburetors on a stock v-8 and expect it to work

Many factories did.

I have a 54/235 with fenton's and 2 Rochester's with a offenhauser manifold and it runs great. 12-13 mpg around town but on the road i get 20-23 mpg.

yeah those stock twin carbureted engines were rather heavily modified from the factory, they were designed to run with that set up. you couldn't put that set up on the low end grandmas version and expect it to work. They used the better heads, the low restriction/dual exhaust, higher compression, hotter cams, all the stuff you need to do to make all that carburetion work. They didn't "just throw them on"

You mean like the Olds, Buick, and Cadillac motors?
Or like the 318 poly?
Or the Adventurer?
Or Chrysler 300
Or Ford Interceptor?

Yes, they did.

Just a update on the dual carbs sorry I didn't use duals went with triples .Installed them on a offy intake .The engine is a GMC 302 very mild cam special grind for the set up.Drove the truck ran great no problems like the others here talked about .I have the truck down now working on paint and body work ,not enjoying it at all !
Good luck to everyone with duals.

you can not "just throw dual carbs" on the small valve, low compression single exhaust smog engine that came with a 2 barrel and expect it to work. I looked up the specs on those engines you are talking about, they were modified in the factory, (didn't I just say that?) not the small valve, low compression, single exhaust smog versions with dual 4 barrels thrown on top. But then again I understand how engines work. But that isn't even the point, the point is, any engine of any configuration V-8, V-twin, inline 4, inline 6, V-4, well any engine, like I just said, can benefit from headers (AKA low restriction exhaust) and most likely a bit more carburetion (unless of course they already had 2 or 3 carburetors) given the appropriate internal modifications. The heads on these engines are pretty atrocious, but they can be improved. As far power is concerned I have seen a 292 putting out 485 HP, and have read articles where they were getting 900 HP out of a 302 GMC,(true it didn't have dual carbs, it had a wayne 12 port head with 6 injectors running alcohol...) I don't know what kind of power you can get in your part of the world but where I come from that is very respectable, and to top it off it would be somewhat unique, not the "hey lets put a crate motor in it" sheep mentality, I prefer to do some thinking on my own. I will give you the benefit of agreeing the V-8 would be easier, cheaper, and they ARE very effective. But to say these modifications do nothing to an inline six is incorrect.

Hey Jerry,
Can I hop up my stock carb ? Or what larger carb... do you recommend ? For my 261 ?

It takes some creative machining and welding, but I'm fond of modifying the stovebolt intake to accept the small-bore Rochester 2 barrel carb that was used on Chevy 265 and 283 V8's. If your 261 is stock displacement and running a stock cam, the 265 2-bbl. should be pretty close without doing a bunch of jet tinkering. A bored, stroked and hot-rodded 261 would probably work better with the one jetted and calibrated for a 283. I believe you'll get better performance and have fewer headaches with a single carb capable of flowing more CFM than you will with 2,3,4, or a dozen carbs on the same engine.
Jerry

finally got your saying. I like it. I'm slow but I get there.

On my 261 that is .060 overbore (270 ci) and dual fenton headers, I am using a single Holley AA1 (2-barrel with adjustable jets) from a 302.

http://www.carbkitsource.com/carbs/tech/Holley/2100-index.html

You might also consider a Zenith from a GMC 270?

Can a Weber 32-36 carb be re-jetted to work good on a 261? If anyone has done this, what size jets are needed? Dave