[wooftfd]

I did a couple of searches, but thought I'd put this thread up, see if anyone else went down this path...
Its a 64 421HO, .60 over, 068 cam (in roller profile), CR lowered to 9.5. 716 heads, mild porting done, Ram air manifolds, tripower with main jets one size up from stock. MSD HEI. Builder left the distributor out of the box setting, mech advance 21 deg, heavy spring for 4000 rpm all in. 12 deg on vac advance, (14 deg showing at idle). Stock for the motor is 6deg, but it runs better at about 12. With the factory setting on the mech advance of 21, im not hitting the 34-35 degrees folks talk about, and I feel like 4000 is a bit low for the "all in"?

anyone out there got some thoughts?

[tom s]

I run 12 int and 36 total on mine.Tom

[wooftfd]

Tom, do you know what rpm you get to total advance?

[Goatracer1]

How heavy is your car and is it manual or auto trans? If auto what do you have for a torque converter?

[wooftfd]

haven't run it over a scale, but think about 3400, and it has a TKX 5 speed in it...

[tom s]

All in at 2500.Tom

[Goatracer1]

I'm with Tom. That's as good a spot to start as any.

[Dick Boneske]

We always aimed for 12 degrees initial and about 34 degrees all in by 2500 rpm. That should work for your 421. If you want better fuel economy, adding vacuum advance will help, but be careful. The factory advance diaphrams often put the total advance into the 55-60 degree range. Dan Whitmore said that about 52 degrees total advance is OK. That's how I have both my 428's set up.

Your Tri-Power, with that cam and heads should be jetted .062 or .063 center and .073 end carbs. You also can improve idle and low speed operation by enlarging the idle tubes to .038 and idle bypass restrictors to .050. It may also help to cut about five turns off the power valve rod spring. I aim for between 125 and 150 grams of pressure to move the rod. This keeps the power valve closed under light acceleration. Stock s[ring pressure is 200 grams.