Attached is an article written by Lars Grimsrud covering the best vacuum advance cannisters for performance engines.
I recently bought the HEI distributor used in GM performance crate engines, #93440806.
The article written by Lars says this :
The “AR12” can is the most versatile and user-friendly unit for a good performance street engine.
Part # VC1838 AR12 (originally came on 1975 350 Buick) advance starts at 7-9" vacuum , total advance is 14 degrees @ 10-12" vacuum
These are still available. I bought one from Autozone, Part # DV1838, $18
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From the attached article :
Most GM V8 engines (not including “fast-burn” style heads), and specifically Chevys, will produce peak torque and
power at wide open throttle with a total timing advance of 36 degrees (some will take 38).
Also, a GM V8 engine, under light load and steady-state cruise, will accept a maximum timing advance of about 52 degrees.
Some will take up to 54 degrees advance under these conditions. Once you advance the timing beyond this, the engine/car will start
to “chug” or “jerk” at cruise due to the over-advanced timing condition.
Anything less than 52 degrees produces less than optimum fuel economy at cruise speed.
The additional timing produced by the vacuum advance control unit must be tailored and matched to the engine and
the distributor’s mechanical advance curve.
I recently bought the HEI distributor used in GM performance crate engines, #93440806.
The article written by Lars says this :
The “AR12” can is the most versatile and user-friendly unit for a good performance street engine.
Part # VC1838 AR12 (originally came on 1975 350 Buick) advance starts at 7-9" vacuum , total advance is 14 degrees @ 10-12" vacuum
These are still available. I bought one from Autozone, Part # DV1838, $18
-------
From the attached article :
Most GM V8 engines (not including “fast-burn” style heads), and specifically Chevys, will produce peak torque and
power at wide open throttle with a total timing advance of 36 degrees (some will take 38).
Also, a GM V8 engine, under light load and steady-state cruise, will accept a maximum timing advance of about 52 degrees.
Some will take up to 54 degrees advance under these conditions. Once you advance the timing beyond this, the engine/car will start
to “chug” or “jerk” at cruise due to the over-advanced timing condition.
Anything less than 52 degrees produces less than optimum fuel economy at cruise speed.
The additional timing produced by the vacuum advance control unit must be tailored and matched to the engine and
the distributor’s mechanical advance curve.
WHY I have No Idea! and Pert tech support Sucks IMHO
