amc 401 Total Timing Advance

[rixcj]

Hi. Does anyone know what the total timing advance is for a 401 ( guessing somewhere between 32-39)? Thanks, Rich.

[BREK]

Well it's not a 401, but my 390 made the most power on the dyno @ 36

[rixcj]

Thanks, Brek. But isn't this info in some sort of jeep bible, or FSM. Isn't this info also provided with some new cam kits?

[BREK]

I'm sure the info is in a tsm, my comp 292h cam kit did not come with any of this info in the box all it came with was a cam card.

[ironman_gq]

I think 36 is the generally accepted mark for max power

[rixcj]

Well,it seems that the general consensus is 36, so I'll go with that. Thanks!

[donwag]

Performance American Style (AMC factory performance guide) recommends 38-40 degrees total advance and all in by 3K rpm.

I used this guide on my 401, curved my MSD dizzy accordingly. Runs great.

[mike4089]

how do you go about setting the timing advance exactly??? i have a 360 that i believe i set the timing at 5 degrees when at idle...but how do you get it to 36-38 degrees above 3000 rpms....also is 5 degrees enough at idle...my motor runs a little warm always around 200-210 and i was told that maybe a change in the timing could cool it down a little

[tufcj]

I run my 390 at 14 initial and another 24 mechanical for a total of 38 degrees.

Mechanical advance is usually adjusted with springs, weights, and a stop, but how its done varies with the manufacturer of your distributor. The factory points style is basically a GM system, so you can use a GM recurve kit. 78-up electronic is Ford, there should be kits made for that.

I run a Mallory Unilite, they make a recurve kit and tool to adjust mechanical advance.

Bob
tufcj

[AMX69PHATTY]

It's debateable, but there is a write-up floating around out there on the web about attaching the Vacuum Advance to MANIFOLD Vacuum rather than PORTED Vacuum to help an engine run cooler. A lean mixture burns much slower than a rich mixture and idle mixture is adjusted to lean best idle so the addition of the vacuum advance at idle helps it run cooler cleaner and smother. Trick is to get the correct Vacuum Advance canister that will not "hunt" at idle depending on your engine vacuum at idle. Vacuum Canister should give Full Advance at 2 inches lower vacuum than engine manifold vacuum at idle.

Agree with the 36-40 total by 2500-3000 rpms, NOT including the Vacuum Advance.
Total of initial adv, mechanical adv, and vacuum adv, is about 50-54 degrees.
The Initial timing really doesn't "matter", what matters is with full mechanical advance, and NO vacuum advance hooked up, the total should be 36-40 degrees and the initial ends up being whatever it is.

Stock Advance set-ups are very conservitive and set-up with warranty in mind
and far from being what works for the best power and performance.

What Distributor are you running ?

Anyone running a Delco Points Type Distributor that wants to try attaching the Vacuum Advance to Manifold Vacuum,
I have For Sale the illusive apparently discontinued "desireable"
B28 Vacuum Advance Canisters mentioned in that article for the small cap Delco points type Dizzy.
It's compatible if the dizzy has been converted to UniLite or Petronix, etc.

Specs for the B28 Vac Adv Can:
Adv Start @ 3-5 inches of vacuum
Adv Fully @ 6-8 inches of vacuum
Total Adv = 8 deg Dizzy / 16 deg Crank