HEI Vacuum Advance Adjustment

Tynan918

Royal Smart Person
Aug 2, 2021
1,112
63
I bought a brand new HEI distributor and it has an adjustable vacuum canister that I have never touched since I bought it and installed it.

Right now I have my engine base timed at 6 degrees TDC @ 500 (factory specs), and I cannot shut the engine off after a drive without the engine dieseling after I cut it off.

There's no way I'm too far advanced at 6 degrees TDC.

I have recurved the distributor by replacing the factory medium springs with some aftermarket light springs but I have never adjusted the vacuum advance canister and I think that's what's causing my issue of being too far advanced and causing the dieseling..
 

MonteLS_84

Apprentice
Jul 28, 2021
63
8
I bought a brand new HEI distributor and it has an adjustable vacuum canister that I have never touched since I bought it and installed it.

Right now I have my engine base timed at 6 degrees TDC @ 500 (factory specs), and I cannot shut the engine off after a drive without the engine dieseling after I cut it off.

There's no way I'm too far advanced at 6 degrees TDC.

I have recurved the distributor by replacing the factory medium springs with some aftermarket light springs but I have never adjusted the vacuum advance canister and I think that's what's causing my issue of being too far advanced and causing the dieseling..
What is your total timing at? That would matter more than your initial in this regard.
 
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Tynan918

Royal Smart Person
Thread starter
Aug 2, 2021
1,112
63
What is your total timing at? That would matter more than your initial in this regard.
Total timing was set to 36 without vacuum advance connected. Initial Timing with vacuum advance connected at full manifold vacuum is damn near 60° BTDC...in gear RPMs are 700-800 and the car runs great, but diesels at shut off.

I'm told to just disconnect the vacuum advance and set total timing 34 and go up 2° until it pings or backfired at WOT...
 

airboatgreg

Comic Book Super Hero
Oct 2, 2016
2,750
113
What is your curb idle speed in drive and neutral? How many miles on engine?
 
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xcookpac

Greasemonkey
Mar 15, 2012
165
43
Lower idle speed. Alternatively. Shut engine off with transmission in gear (and then shift to park).
 
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airboatgreg

Comic Book Super Hero
Oct 2, 2016
2,750
113
Idle to high in drive. See if vacuum to distributer at idle. If it is move vacuum line to ported vacuum(IE vacuum when throttle is opened) Readjust carb to 600-650 in drive.
 

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