Advance the timing before TDC. Why?
I've tuned it to about 9 degrees before TDC.
Why do I want it tuned that way?
Much of this has been more or less answered in the thread.
Because people here have some sense of what a 318 with that cam will need, the range of initial timings suggested here is going to be about right.
Your hot rod cam has more valve overlap at idle than stock. This means more exhaust dilution and slower burns. That's why it needs more time at idle. You'll have to experiment a bit because the more compression, the more efficient the burn.
A non-smogged 4 bbl 273 had initial timing spec'd around 10* BTC at 650 rpm. Tech's had discretion to bump that or reduce that depending on fuel quality and elevation. (That's the last non-CAP high performance factory smallblock, and your cam is more radical)
Still related to ignition. What would you suggest for a distributor to replace stock?
Stock is fine.
If it has an early CAP or CAS advance curve (initial timing of TDC or ATC is a big clue), then the advance off idle is going to be too long and too fast.
If so, then clip the start of the curve by welding up the inside of the slots. Or, send it to
@halifaxhops and he'll set it up for ya. (But yes you have to pay him. )
I'd start by measuring the timing from idle, as slow as you can go, to at least 2800 rpm.
Then plot that.
From there you can make decisions
