Distributor setups for L78 or L72 engines?

[Jeff H]

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I'm not a fan of the GM hei pieces...while they will work, *IMO* they look out of place, and believe it or not a good points system can work just as well. Anyway, when is your total timing in? And what compression & pistons you running?

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Rob, the motor is a bit of a mystery to me since it was built by a previous owner. All I know is it has the 820 oval port heads which probably lower the compression a little, the stock L78 intake, Holley 750(that's been messed with), the GM HEI distributor and headers. As for cam and pistons, I have no idea but will assume they are stock. I don't plan on racing the car and I'm not worried about 100% stock appearance at this point in time. Regarding the vacuum advance, I'm reading around 36 of timing with the vacuum adv disconnected. When I reconnect it the total timing jumps up to around 50 or so. Is that correct? Should the vacuum advance still be adding in at higher revs? I don't get any pinging so it sounds fine.

[@wot]

The vacuum advance unit is non adjustable an adds 15 degrees to the mechanical advance on a stock L78, yielding 51 total timing. If you are positive there is no detonation, check the plugs to confirm, leave it alone. If it is high speed detonation, back off the timing a couple of degrees. If you detonate under load, its probably the too much vacuum advance. There is NO vacuum advance at full throttle, engine vacuum will be close to zero.

[@wot]

My L78 points distributor has a max mechanical advance of 18 degrees all in by 2750 rpm ( autommatic car). There is another 18 degrees on the crank for a total of 36, with no vacuum advance. The car has about 12 inches of vacuum at 900 rpm in drive.

[WILMASBOYL78]

Dean, that's a good setup for that motor...everything before 3,000 rpms
..just when an L78 starts doing it's thing. then hold on till 6500-7000 or whatever your brain can stand....

wilma

[@wot]

yeah... it seems 3000 rpm is the on/off switch for this engine. Once it is above 3000, you're really starting to roll. Although not applicable with the HEI, the dwell angle I use is 30 degrees.