amc 401 Total Timing Advance

[mike4089]

what if your running an HEi unit....how do you go about setting that?? i think i need to look at my timing becuase i think i only set it at about 5 degrees at idle

[AMX69PHATTY]

Same applies to HEI Dizzy's.
Just the Mechanical Advance Recurve Kits are different part numbers
and the Vacuum Advance Cans are different part numbers.
I prefer the "stock" style off the shelf Vac Cans to the "pricey" Adjustable ones
available from Crane, Accel, MSD, etc.

On HEI's the Total Mechanical Advance is determined by the
Weights, Springs, and the Mech Adv Cam Plate supplied in the Kits.
On Points Type it's determined by a Pin, Slot, and a Bushing
that comes in the Kits and goes on the Pin to limit travel in the slot.

For the HEI, the Vacuum Can to get is:

Desireable "HotRod" Vacuum Advance Canister for GM HEI Distributors

AR15 - Stamped on Flange of ALL Brands

#1973508 - ACDelco
#DV1843 - Wells - AutoZone
#VC1843 - Echlin - Napa
#VC262 - Standard Motor Products - CarQuest
#DR347 - Niehoff - where ?
#V399 - Borg-Warner - Advanced AutoParts

Start Adv @ 3-5 inches of Vacuum
Fully Adv @ 9-11 inches of Vacuum
Total Adv = 7.5 deg Dizzy / 15 deg Crankshaft

"HotRod" Timing Advance Set-Up for HEI Dizzy:

14 deg Intial Advance set with NO Mechanical or Vacuum Adv at idle
24 deg Mechanical Adv all in by 2500-3000 RPM's
38 deg Sub-Total Initial and Full Mechanical Advance
15 deg Vacuum Advance
53 deg Absolute Full Total Potential Advance

... with Vac Adv Can attached to Manifold Vacuum
14 deg initial Advance
15 deg Vacuum Advance with Engine Vacuum at Idle above 11 inches
29 deg Total Advance at Idle with NO Mechanical Adv coming in at Idle

Be careful of Detonation.
Reduce Initial advance, or the rate and/or amount of mechanical if it pings.

A Dial-Back Timing Light is a "must have" to get it set up right.

[mike4089]

what does it mean when the motor has come up to running temperature and you get done driving and when you go to start the motor back up it turns over really slow for a couple of revs then turns over like normal and fires off....mine does this sometimes and i didnt know if it was the timing or what...i have a brand new battery so i know its not that...

[tufcj]

Your initial timing is probably a bit too far advanced. Try backing it down a couple of degrees.

Bob
tufcj

[AMX69PHATTY]

Agree, first guess would be too much initial timing making it difficult to turn over and start-up when up to temp. In Jegs and Summit they offer "Starter Saver" electronic boxes that reduce the spark advance by 10 or 20 degrees when cranking to help prevent this, or back off the initial timing as mentioned. Old school drag racers, and I guess even nowadays, completely locked down the distributor advance internally and sat the timing at 36-40 fixed total and used the "Starter Saver" to back it off so it could be easily started.