timing outta wack
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Drifting
Joined: Oct 2005
Posts: 1,615
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From: Forth Worth TX
No vac, rev engine to get 36*. What RPM? Based on your answer, will need to adjust springs/timing/etc..
From your statement above, if you are only getting 21* @ 4000rpm without vacuum, you have a problem.
Connecting the vacuum at idle and reading what the timing is was only to determine if you are using ported or manifold vacuum. You aren't making any timing adjustments at this point. Manifold vacuum is preferred over ported vacuum for the street.
Again, take it to someone who understands what they are doing and can TEACH you. A local speed shop, Corvette club, etc..
Last edited by Revi; Sep 13, 2013 at 09:40 AM.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Idle with no vac is at 8*. Idle with vac is 24*. This tells you that your vac can is pulling 16*.
4000 rpm, no vac 21*. This tells you that your mechanical advance has advanced by 13*. That's pretty low, it should be closer to 20* or so, for a figure of around 28*. It's probably not fully advanced at that rpm.
With vac 4000 rpm 36*. This is telling you that your vac can is pulling 15 degrees of advance. 15, 16, it's probably just a slight error in reading it.
Conclusion: You probably need lighter springs to bring the mechanical advance in sooner, and about another 8* of initial for it to be at 36* all in. This would put your initial at 16*, initial with vac at 32*, all in mechanical advance at 36*, and cruise at 52*. (assuming your distributor is giving 20* of mechanical advance.) It ain't rocket surgery, man.
Scott
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Take off the dist cap and rotor and do a visual and rotate the shaft. If it snaps back and the weights are moving freely then it ain't that.
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Le Mans Master
Joined: Mar 2008
Posts: 5,948
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From: Oxford MA-----You just lost the game!!!!
Race Director
Joined: Mar 2006
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From: Florida
4 speed
Now that you have it running good enough, just take it to a car show or local get together and ask anyone with any GM there if they can show you. Visual might be best and I'm sure many there would offer, might start a mutual car friendship.
DUB
You show far too much class.
Now that you have it running good enough, just take it to a car show or local get together and ask anyone with any GM there if they can show you. Visual might be best and I'm sure many there would offer, might start a mutual car friendship.
DUB
You show far too much class.