timing mess
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Joined: Jun 2010
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timing mess
I have a 79 vette 350, edelbrock intake ,edelbrock 600 carb,sportsman 202 heads elgin E920P cam 480 lift , msd streetfire distrib ,I set timing at idle with vacuum off distrb, to 12 degree ,when I plug vacuum hose back in timing reads 45 degrees at idle ,is this right ,car always has terrible rich fumes ,I've tried different carb, still smells rich, ,what do I do
Advanced
Joined: Mar 2006
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I have a 79 also, and found the Harmonic balancer is set in
rubber. After years the outer rim will turn and the timing marks
will shift. My marks shifted many deg. Replaced with a
very good after market no problem setting timing.
rubber. After years the outer rim will turn and the timing marks
will shift. My marks shifted many deg. Replaced with a
very good after market no problem setting timing.
Pro
Joined: Oct 2006
Posts: 734
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From: Bryan Texas
I'd be thinking you are getting mechanical advance also when you hook up the vac, are you idleing it back down after you hook up the vac before checking the timing? That vac advance pod should be adjustable. Use an allen wrench in the vac port. I'd probably rubberband the weights in the dist and then adjust the vac pod to get like 16 degrees of advance. It sounds like you are using manifold vacuum, if not, do... at least while you are adjusting things.
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Joined: Jun 2010
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yes using manifold vac ,should the timing ever be that high ,1..what should I set initial timing to with vac unplugged ,2.. what should timing be when vac plugged 3.. what should timing be when raising rpm wot
Burning Brakes
Joined: Dec 2005
Posts: 992
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From: Baldwinsville, NY
You should read Lar's papers about timing. I have set the timing with the vacuum plugged and all in at 32 degree at 2500 to 3000 rpm then the idle timing is about 10 or so. When I reconnect the vacuum the timing goes up to about 25 and max with no load on the engine and 3000 rpm is about 48 to 50 degree. I have Vortec Heads and the max timing is 32 to 34 but regular SBC might go as high as 36.
Go to VetteTech;
http://www.lbfun.com/Corvette/Tech/vettetech.html
Here is on of Lar's papers on HEI distributors.
http://www.lbfun.com/warehouse/tech_...I%20Tuning.pdf
Take some time an read up on it, you may not end up an expert but you should be able to get the timing set.
Go to VetteTech;
http://www.lbfun.com/Corvette/Tech/vettetech.html
Here is on of Lar's papers on HEI distributors.
http://www.lbfun.com/warehouse/tech_...I%20Tuning.pdf
Take some time an read up on it, you may not end up an expert but you should be able to get the timing set.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Very typically, a distributor vacuum canister will make about 15 degrees of crankshaft advance. If you are getting 30 degrees of vacuum advance, that is not right.
Not unusual for a smallblock to be happy with 12 crank degrees initial timing plus 20 or 22 degrees of mechanical advance, for a total of 32 to 34 degrees at cruise RPM (plus any vacuum advance).
Not unusual for a smallblock to be happy with 12 crank degrees initial timing plus 20 or 22 degrees of mechanical advance, for a total of 32 to 34 degrees at cruise RPM (plus any vacuum advance).
