[78MayanW87]

Experts—I have a 400 with #62 heads and HEI. What would be the recommended base timing for that setup? Thanks for the help!

[chuckies76ta]

I'm no expert, but you should post that question in the street section. More traffic there. Do you know what your initial timing is now? I like around 15 to 17 deg in engines I have had. I even went so far as to make custom stops for my total timing. I usually work backwards from total timing to my initial timing. So for example if my total timing is 34 deg and I want 17 initial, I will set it up for 17 mechanical advance. Are you running any vacuum advance on the distributor?

[Kenth]

Is it a Pontiac original HEI and what application number?

[nUcLeArEnVoY]

Need more info. How much compression are you making? What's the cam specs? Late 70's T/A's had really high initial timing due to their low compression and heavy advance springs - you'd only get around 14-18 degrees of advance by 4500 RPM, which is why their vacuum advance canisters add a ton of advance (as high as 25 degrees at 11" of vac for W72 cars) to compensate.

Your motor originally would've probably had 18 degrees of initial timing as originally equipped. This one with 62 heads, tho, not sure. You're better off just tuning for total timing, and then whatever the initial lands at and the motor likes it, is what you go with as long as it's not so high that it kicks back the starter on a hot start, and not so low that she starts running hot at idle.

[Skip Fix]

In '78 both different HP motors and auto vs manual had different advance curves and base timing per my shop manual.