Pontiac GTO Forum - View Single Post - Distributor Tuning
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post #5 of (permalink) Old 04-14-2019, 08:28 AM
cij911
 
Join Date: Oct 2017
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Thanks guys!

A few points of clarification:

(1) PJ - I did not say that my car likes 16* of initial, rather that is what I was told it should be around by my friend and seems to sync with LemansGuy's advice (albeit slightly lower).

(2) BigD - I have the car set for 36* total and the car runs strong. My questions were a bit more advanced and were focused more on the transient response and moderate load conditions (not wide open throttle or idle). My belief, even though I don't hear or see any issues, is that I am running too much timing because of my vacuum can advance (25*) and the amount of mechanical advance (30*) my distributor has.

So to recap my current setup:

Total timing = 36* (comes in by ~3400 rpm with Mr. Gasket black springs)

Initial timing = 6*

Idle timing = 31*

Vacuum advance = 25*

Mechanical advance = 30*

So if I understand this correctly, under light loads or engine braking, I could be seeing timing in the ~61* range (6+25+30) which seems way too high and is caused by two things the WRONG vacuum can and too much mechanical advance. All of the great engine builders appear to want timing to be more like 10 - 16 base, 10* vacuum, and 20 * mechanical, which at most would be ~46* at moderate loads.

I have a 10* vacuum can and will pull the distributor and swap out and log the affects of AFR and performance. I will report back.

Thanks again for your help.

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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