Intial, mechanical, and vacuum advance settings

76BBSub · October 27, 2001

After finding that my mechanical advance plates were stuck together (again!) I broke down and bought a new Accel HEI distributor. What a difference! It comes with the new module, cap and rotor, and I already had the Accel Super Coil on my old distributor so I swapped it over. The old Sub used to only rev to about 4000 RPM under wide open throttle, but now it will run up to about 5000 RPM before shifting. Also, transitions between the shifts are smoother, probably due to the mechanical advance working smoothly.

But this post is about ignition timing. I spent a couple hours yesterday dialing in the initial, mechanical, and vacuum advance to what I think is the optimum setting based on the SOTP test...seat of the pants.

Here's what I'm running:

16 degrees intial

33 degrees mechanical, all in at about 2200 RPM

12 degrees additional vacuum advance at idle, for a total of 28 degrees at idle

Rock solid 20" of vacuum at idle.

This is on a 454 with 100K miles, fresh valve job, Performer intake, cermamic coated headers, 2-1/2" pipes in a '76 Suburban.

What are you guys running? (other vehicles besides trucks are OK too for comparison purposes).

Jeff

Torque Junkie · October 27, 2001

In my 79 chevy, 350/TH350, Edelbrock performer cam, intake and 600cfm carb, Stock ignition system (or whatever came with the most recently rebuilt engine)

Unfortunately, my dail has no visible numbers, so these are just ballpark figures.

12-14 Deg. Initial (just before the first tooth of the dial)

~10 of Vacuum advance, at idle - pulling between 10 and 12" at idle

Mechanical I have no idea. I know it does advance it when reved, but how much and when I don't know for sure.

This seems to be running the best yet. In case anyone else doens't know, I just recently replaced a faulty vacuum advnace canister, and it seems to be making a huge difference at my idle and low-rpm performance and smoothness.

Who knows, maybe a new ignition system is going to bump itself up in priority on my wish list......

-Mike