Skeeter Vaughn

I'm having issues with the motor in my car. It's a 77' 403. It dies at an idle, shakes like it is missing and when you get it past idle it smoothes out and runs good. It sounds like it is running out of gas to me at an idle?. So far I had the carb rebuilt new throttle shafts and kit, vacuum lines, intake and valve cover gaskets, EGR valve, It has new plugs, wires and the rest of the goodies. It holds about 16 pounds of vacuum at a faster RPM. May be some of you all have had this problem before. Any input would be great. It has to be something simple, yet to well hidden for me. Thanks!

MDchanic

Most obvious explanation is a vacuum leak.

Check around all of that new stuff you put on it - you may have a hose off.

- Eric

ah64pilot

I agree. I spent $80 at an auto shop when I was 17 for the same problem with a 455. After fixing it I ask what they had done...found out they just put a rubber cap on a vacuum port I left open.

Check for something obvious, most of the time we just forget something.

Skeeter Vaughn

Found out my problem. Nothing to do with the intake or the vacuum. The carb had internal cracks and it was sucking air. I pulled off a carb from my parts car and had it built and it runs great now!! Problem solved!!

joe_padavano

Which is pretty much the definition of a vacuum leak...

Skeeter Vaughn

Yes it was a vacuum leak, just not in the usual places! Oh, and by the way, Where were you when I had the initial problem? Yet quick to point out the obvious?!!

Olds_71_442

I'm assuming he didn't answer before because he was thinking vacuum leak like everyone else.