I think we figured it out, when we installed the intake manifold gaskets we installed them for an 83 elcamino, not an 82 c10. there were metal EGR port reinforcements that were needed/not needed depending on the model and year.

so we are going to pull the intake and I'm willing to bet the EGR port holes in the gaskets will be leaking. causing the blow back.

Make sense?

 

hook up a vacuum gauge to intake manifold vacuum and see what it does. To me it sounds like it could be a wiped cam lobe.

 

its possible, though we did check the rockers and they are all lifting about the same and all pushrods spin.

 

better keep an eye on the oil, make sure gas is not getting mixed in with oil. commpression test on all cylinders would be a good start.

 

just did compression test. 160-170 psi on on cyls. with the motor cold. those numbers done seem right but thne again we have no idea whats been done to this motor.

 

those are good numbers for a stock 350, i would suspect electrical. try running it in a very dark place, open hood and see if you get a light show from anywhere around the plugs, plug wires or distributor cap.

 

well, we were all wrong.. it was a completely plugged cat.

 

lol, constipated eh,,, strange that it was coming back up the carb.

 

If it is gas spitting out of the carburetor while the engine is running it is either the timing too retarded or the intake valves are leaking. It sounds like a timing problem…

 

^ That was already suggested to him. However he found the problem, a completely stopped up cat converter.
Nothing strange at all about it spitting out the carb because of that. Put a tight cork in your butt (exhaust), and pretty soon you're going to start throwing up out of your mouth (carb). The stuff that's going in has to get out somehow.