Mid 70's 460 timing and distributor tuning
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AirForceVet
Joined: Mar 2004
Posts: 612
Likes: 127
From: Spotsylvania,Virginia
Mid 70's 460 timing and distributor tuning
I have a mid 70's 460, .030 over, A2A heads slightly modified (knocked the EGR hump out with a burr) Stealth intake with 750 Holley. With the vacuum advance disconnected, set the timing at 8BTDC, close to 20 inches of vacuum. Runs and responds fine, when I shut in down and reconnect the vacuum line to the distributor it doesn't want to start right off, it acts like it's to far advanced. If I leave the line disconnected from the distributor it starts fine. I am using a Pertronix electronic distributor which I just installed. I have not done anything to the distributor except install it. Looking for suggestions or advise, one other question, the timing pointer has a site hole, what is that for, I adjusted the timing to the edge of the pointer.
Cargo Master
Joined: Oct 2020
Posts: 2,685
Likes: 789
Vacuum advance really shouldn't come into play at all during cranking and depending on where you have it connected it might not do anything at idle either. What I've found many times is that an aftermarket vacuum advance will just go too far and give so much advance when the engine is revved up and at part throttle that it causes a misfire. Usually I get the base timing correct first and then add the vacuum advance. I just adjust it so that it adds maybe 5-8 degrees max so if I'm running 34 degrees total timing I don't want to see it go above maybe 42.
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AirForceVet
Joined: Mar 2004
Posts: 612
Likes: 127
From: Spotsylvania,Virginia
Yeah Dave, I'm doing some research on YouTube on my particular distributor, I'm thinking I may have to change the springs on the centrifugal advance, You are right, the vacuum advance shouldn't come into play during start up. It actually runs good, no pinging, no popping through the carb, very responsive. Just that sometimes its hard to start after shut down and wants to kick back while cranking sometimes.
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