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engine timing and tuning
#1
All,

recently, I noticed the engine was developing some significant pinging under heavy load (like when you go WOT because you like that kind of thing). Some background: I have points/condenser ignition 302 2bbl. I have ported vacuum which has generally worked pretty well - car has generally run pretty great. I have had one nagging issue where I have to run with the distributor rotated as far as it will go towards water pump. In general it was fine there, but it has bothered me that I couldn't get to zero initial timing. Against water pump was 12-13 deg of timing if I recall. It would generally pull about 15in vacuum at 800 rpm idle.

I went around the engine to check the cylinders and plugs. All cylinders produce between 125 & 135 psi, and all plugs were generally clean and the ceramic was a nice tan color, and gaps were all good at .034.

Since pinging usually has something to do with timing advance, I was curious if I had developed vacuum leak somewhere, so I looked for one. Everything seemed ok (hoses have been replaced in the past year or two). but I checked the vacuum advance module with a vacuum brake bleeder, and found that the line coming off the side of the module (not the axial port) could not hold vacuum.

I changed the vacuum advance module out, and still couldn't get it to run very well. It was rough and irregular. I was frustrated by the inability to get to 6deg initial timing, so I re-stabbed the distributor one cog over. I also put in new points and condenser. The new points actually improved things some too.

With the distributor re-stabbed, the car starts and runs great up to 2k rpm. Now it runs ok with the dist rotation in the mid range, and all the way over to the water pump is too far. Initial timing is around 6degs, and it idles real well, and generally seems normal. Pulls around 15in vacuum (15 seems low to me - should be 18-20 right?). But, when I really put the gas to it, I get a lot of hesitation, and it generally runs badly. it's the 2500+ rpm range that I have the problem.

timing at ~3K rpm is high 20's (thats with both vacuum hoses on vac advance). Seems low... should be over 30 but not more than 36 right? How do I get it there? I remembered I had not adjusted the hex nut inside the vacuum module axial port, so I went out and played with that some, maybe some improvements, but nothing at the high end.

All that to ask, how do i hold the good situation at low RPM, and adjust the high speed advance up to where it needs to be? Seems like I'm almost there, but Im kinda stuck at this point.

Pics of The Car
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