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Old 06-22-2007, 04:46 PM
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350 timing

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

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Old 06-22-2007, 04:54 PM
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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?
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Old 06-22-2007, 04:59 PM
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You got a leaky spark tube...
 
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Do you have a vacuum leak somewhere?
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Old 06-22-2007, 05:01 PM
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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?
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Old 06-22-2007, 05:16 PM
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You got a leaky spark tube...
 
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Cam won't change ignition timing. Vacuum leaks will make the engine idle high and cause you to chase your tail...
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Old 06-22-2007, 05:21 PM
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Sounds like you are setting the timing correctly. 12 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 10-12 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.
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Old 06-22-2007, 07:40 PM
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I also noticed that the idle speed varies from 900-1300 within seconds, shorts bursts up, then drops down. Vacuum?
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