The advance bushings included with the MSD Pro billet distributor only allow a 18deg advance curve.
A special 10° and 14° limit bushing is available to cure this. It adds another $30 to the cost.
MSD does not sell this.
Fix what you got, for peanuts.
Crane and Mr gasket both offer and good replacement adjustable vac advance for HEI distributors.
The vac advance on your MSD HEI style distributor should be adjustable with a allen key. The allen key adjusts the spring rate
and rate of vac advance but not the vac adv stop limit.
It does not have a positive stop limit. You can fabricate this positive limit stop for the vac adv
for peanuts too.
But first verify the amount of vac advance travel and potential vac advance limit by testing with a hand vacuum pump
and timing light to see the limit you got at highest applyed vacuum. Should not be more than 15deg when highest vaccum is applied with the vacuum pump.
If it never gets beyond 12-15deg you are good to go.
The at rest point of the vac advance linkage arm also effects the distributor cap/rotor phasing alignment because it
moves the position of the mag pickup star ring. Poor cap/rotor phasing alignment causing all sorts of ignition issues like crossfire
cap arcing, detonation priignition , misfire, crossfire potential engine damage when out of wack.
This is how you blueprint a HEI disributor, reguardless of brand or price.
Last edited by F-BIRD'88; 09-09-2012 at 02:30 PM.