Hello,

I had posted earlier about carburetion problems after new Rochester install; several old hands had tried and not succeeded in keeping it from either not starting (cold) unless you depressed the choke manually; then shutting down as soon as you dropped it into gear cold, hot, warm, whatever. The old carburetor had attained performance only slightly better than described. Someone pointed out they had detected low compression in two cylinders which is bad of course. But I don't see how that produces immediate shutdown, or any other sudden worsening of performance.

At one point we partially reduced air intake by partial duct tape coverage of the front part of the carburetor bowl and it ran like a normal car. Drove it downtown and back.

Obviously this test result cannot stay. I am wondering what we are compensating for? Somewhere else in the system, there is a valve stuck or the vacuum is otherwise severely compromised. I believe it may be the manifold heat valve but have no conclusive proof (taking the engine apart to find that out is, I hope, to be avoided). Or it may be that.

If anyone has any thoughts on this, I would be grateful.

Andrew

 

Look for a vacuum leak around the base of the carb. spray some WD4O or carb cleaner around the base and see if the rpm's pick up. may be a bad gasket seal or warped carb base.

Or could be just a bad carb re-build job.

 

As stupid as it sounds I would check all the vacuum ports on the manifold and at the base of the carb itself.

Did you ever say what kind of Carb it is? I don't remember...

On the Edelbrock performer series carbs there is a hole at the back of the carb base plate that has to be plugged prior to install. Just a thought.

 

Hi--

This is a remanufactured Rochester 4GC. . .I do believe vacuum is imperfect so I will look around at the base and at the manifold as well. I was also thinking that something as lame as a broken wiper fluid tank (which is glass, and which is mostly missing) could also affect vacuum because that is how it operates.

Thanks for your helpful observations!

--AE

 

Here is a picture of it when I bought it in Colorado. . .would love it to run the way it looks! And of course despite the caption it is not a hardtop but a sedan that in 57 mimicked the look of a hardtop.

 

I just rebuilt a 4GC for a '65 442 last week.
Noticed a few intracacies uncommon to most other carbs!
I'd guess an internal leak and/or blockage- take the carb back -