[JG700]

Hello,

I reinstalled a freshly rebuilt 350 (bored 30 over, new rings, pistons, cam, timing chains, valves, etc.) into my 1980 Corvette (L82, automatic) and started it today. I ran it for about 40 minutes running between 2000 and 3000 rpms. I let it cool, then ran it again for about 45 minutes, even drove it briefly around the block. Here's the problem: the timing is supposed to be 12 btdc. When I set it there, the idle runs extremely high (1600+). So I turn down the idle, and the timing is off! What am I doing wrong? I disconnected and plugged the vacuum from the distributor (which drops the rpms), then set the timing, idle etc. When I set the idle to 1000 rpms, it drops to 500 in drive and stalls. How do I get it to idle properly AND be at the proper timing AND not stall in gear? Should I try it with the vacuum attached? Any help would be greatly appreciated.

JG700

[GMC boogie]

I do not know all the details of your engine build but,my first stab at it would be the valve setting is too tight. What camshaft? What converter?

[Blazin72]

Do you have a vacuum leak somewhere?

[JG700]

No idea. I had a reputable machine shop do it. I do know that he used a "better" cam (more lift?). Would that change the timing?

[Blazin72]

Cam won't change ignition timing. Vacuum leaks will make the engine idle high and cause you to chase your tail...

[GMC boogie]

Sounds like you are setting the timing correctly. 12º with distributor vacuum hose disconnected and plugged. I like to connect the vacuum advance hose to full manifold vacuum with the vacuum advance can modified with a stop to allow no more than 10-12º advance. Again,it sounds like a vacuum issue,valves too tight,or late timing...make sure the damper has not slipped and you are getting a false reading.

[JG700]

I also noticed that the idle speed varies from 900-1300 within seconds, shorts bursts up, then drops down. Vacuum?