The Stovebolt Site Forums The Shop Area Engine Shop 235 Carb problems

I just had my Rochester 235 rebuilt by a guy around the corner from me, Larry Isgro. He did a very fine job! So now I have it back on the truck. This is the first time I've messed around with one of these and I'm trying to figure out what I'm doing wrong. When I start the truck I choke it because it won't start any other way and when I put the choke back in the truck stalls out. So I've had the truck running with the choke slightly out and I've tried adjusting the two idle screws but it doesn't seem right, or how it was, and can't seem to figure out what I'm doing wrong.

So I see you are not in a place where your weather is warm. Standard procedure would be to start it on full choke, reduce the choke some but not until it falters and after several maybe five minutes or more you can take the choke off. Does it work that way?

There is only one idle screw and one mixture screw.

The idle screw adjusts the "lever" that is attached to the throttle-rod/gas-pedal. This adjusts the "idle speed" - the RPMs at idle.

The mixture screw adjusts the air/fuel mixture. I think it is recommended that you gently turn this all the way in - gentle turn it in until it "stops". Then, back this screw out 1.5 turns of the screw.

Larry would most likely have set the mixture screw close enough to get the engine started.

When I turn the mixture screw should the engine be running and stay running? While its running and I begin to turn it in, it kills the motor

Make sure you don't have a vacuum leak somewhere...base of carb, wiper motor hose, distributer vac advance etc.

Mike B

Interesting that you say that, because I just realized that the wipers are not working. They were working prior to me removing the carb. What would that have to do with the carburetor and vice versa?

Is there a hole in the outer-middle of the intake manifold (below the carburetor)? That is the port/hole for the fitting/tube for the wiper vacuum hose.

If that hole is plugged/capped, your will have no problems.
If that hole is open, you should hear a sucking sound (a vacuum leak).

Also, how do I check for, isolate, and fix said possible leak?

plug it

Or reconnect the vacuum line going to the wiper motor and fix both issues at the same time...

Mike B

Exactly. Start with the mixture screw a few turns out. With the engine running turn it in slowly till the engine starts to slow down. Then back it out enough to smooth it out, usually about 1/2 turn. That is your ideal setting. The vacuum hose to the wipers hooks to a nipple on the manifold. Hook it up before doing this adjustment.

There is a small open (not plugged) pipe coming from the middle of the intake manifold. However, I never removed anything from there and the wipers and carb (prior to rebuilding) worked fine. So I'm not sure where everything went wrong. I'm new at this stuff and confused. I do hear a sucking sound coming from the (possibly inside) the carb.

And as to my prior questions, I'm assuming that when I turn the fuel mixture screw in the engine shouldn't die?

OKay, I'm going to check for that vaccume hose. I don't remember taking it off.

Well, I'll be damned. The hose was disconnected. I'm not sure how it got like that but I re-attached it with a hose clamp and the carb and wipers run great. Thank you very much for the help.

Glad it was a simple fix!

Mike B

In answer to part two of your question a few posts above, yes the engine should die or come very close to it when you screw the air mixture screw all the way in.
Wrenchbender Ret. gave you the old school way of adjusting the air mixture and it does work well.