Engine: 250
Carb: Rochester B

Problem: After installing long tube headers and rebuilding the carb, my truck will only idle normal with the choke barely open, maybe 1 mm open. If I open the choke the idle keeps climbing until I shut it off or it stalls out. This is with engine cold or warm.

I have sprayed carb cleaner everywhere as I assumed there was a vacuum leak somewhere, but no idle increase.

I also set the mixture screw 1.5 turns from fully seated.

More info:. There is an exhaust leak where the pins are. I purchased new studs to replace those pins, though.

Honestly, I know nothing about carburetors. I'm 35 and this 64 is my first carburated vehicle.

Any help is appreciated.

Sounds like the throttle plate may not be fully closed. I would check the return spring.

Try the idle mixture screw open to about 2 and a half turns and see if it improves. Then screw it in gradually and observe result. If it gets worse, try the other way. It does sound like you have a vacuum leak, but it may be as simple as that idle mixture screw. You have nothing to lose.

Ok, so I took the carb off and apart. I never cleaned the idle mixture screw and it was dirty where it seats. I cleaned that area out

The floats were maybe 1/32" off so I readjusted them.

I also noticed that the power piston was stuck down and wasn't even touching the check ball. I cleaned it all out and it moves freely now. Could this have been the culprit?

New question:

There are 2 oval openings on my carb (see picture) that I am curious about. One was plugged with debris? and the other was clean and clear. Should these be open? Most Rochester Bs I have seen on the web don't even have these.

Thanks!
Jeff

A quick Google of things and it would appear the hole you pictured is meant to be open. See this page: http://www.carburetion.com/CarbID/RochesterID.htm

Well crud. Thank you.

Crud? That what you meant to say?

Sounds like that carb is just full of crud.

Yes. Crud. I hate that I did not find that picture. I was looking more at google images.

We look at Google upside down from here in Australia. Perhaps that is the reason you didn't see the pic. Ha !
regards,Rod.

From the symptoms (idles ok but only if choke is almost shut, even when warm) its 1 of 2 things:
1. Clogged idle ciruit
2. vac leak at base of carb or intake

USUALLY it's #2
I've never had a "B" csrb refuse to idle - always a vac leak.
I guess a really "cruddy" one could do that but I'd look hard for a vac leak, usually base of carb, open hole, etc.

I think you are right on the money with intake leak. I removed the intake manifold and headers to replace the end pins with studs, and I could tell there were leaks. Hopefully I can get it all sealed up. If I cannot with the Felpro gasket I will be buying the thick all graphite intake/exhaust gasket.

Got her running!
https://youtu.be/90bEfvsgSug

Awesome!!! Sounds good! Subscribed to your youtube channel.

Good work Backpayne. Enjoy the ride.

regards,Rod.