The Stovebolt Site Forums The Shop Area Engine Shop dual intake manifold setup

i have a 1954 chevy 1/2 ton. it has a 235 straight six. i just added a dual intake manifold with two rochestor one barrels. whenever i hit the gas while im driving, it sounds like it is going to flood out!! what should i do to adjust this? and also it doesnt seem to have the same ooomph as my original intake with a 1BBL carb. and i dont know if my carbs just need adjusted. when i am doing about 35 it seems as if when i hit the gas that it doesnt have much more power it just slowly speeds up? any help would be great!! thanks

old54truckluvr,

There are a lot of people who frequent this site who have a dual carb 216/236/261. Post a little more information and I bet there will be many opinions.

What kind of intake manifold?

How are you heating the intake manifold?
How?

Are you sure the "choke flaps" are open in both carburetors?
How have you set up the choke (is only one carb choked - by cable ?)?

Did you rebuild both carburetors?
Are both accelerator pumps new (and squirting gas)?

Tim

i have an edelbrock intake. i am sure the choke flaps are open and only one carb is choked. the carburetors have been rebuilt and i dont know about the accelerator pumps but they seem to work. i am not heating the intake manifold. thanks

It sounds like your accelerator pumps aren't working. Redcoat

First, are the basics good?

Are both mixture screws about 1.5 turns out?

Is the linkage adjusted so both butterflies are opening and closing together?

How's the idle once they are warmed up?

Any intake vacuum leaks?

I would doubt both accelerator pumps would be bad on rebuilt carbs - I'm thinking it's probably a combo of adjustment problems.

Both carbs need chokes otherwise your only putting the richer mixture to half the engine. The old Chevies were and still are cold natured engines. Next thing, and it seems to be pretty critical on the dual carbs, is to use the heated intake. The kits are available from Langdon.

Where did you get the rebuilt carbs? Mine were Holly rebuilds with neoprene pumps. Neither one of them pumped anything. NAPA sells the correct leather pumps for the Rochester.

I think you have a power valve problem. You need to modify it so that the part/full throttle mixture is correct. See http://www.inliners.org/tech/tech4.html

My setup works well choking only one carb. What size air filter do you use? I took someone's advice on this board and dumped the little donut filters that you normally see on these setups. I got much taller filters, and it make a HUGE difference!

i have just small air filters that aerent very big at all. but bigger ones will make a big difference, maybee i will try that!

I had a similar problems with 2 1bbl Rochesters on an Offy dual intakeon a '58 235...solution was 2 fold...(1) check fuel pressure...I was getting way too much, put in a NAPA fuel pressure regulator and the "loading up" stopped right away.2)But, bottomline, 2 1bbl Rochesters are way too much caburetion for that 235...Ultimately had to get rid of the Rochesters...couldn't stand the smell of leaking gas and the ugly look of stained carbs, plus the MPG stunk...switched to 2 1 bbl Carters and haven't had a problem since...no leaks,smells and better MPG.

By the way, set fuel pressure between 3.5 and 5 lbs...depending on what works for your situation.

where can i find 1bbl carters at, and how much do they cost? thanks