When I look at the Datamaster displayed advance on my 90 vette, it corresponds to:

= Base Spark Table + PE advance when in PE mode

Is this total advance? or do I need to add the initial advance of 6 deg to get the total advance?

I suspect that it is total advance, because the factory PROM has 34.8 degrees of advance (Base + PE advance) @ 4800 rpm/WOT. If you were to add 6 more degrees that would take it up to 40.8 degrees, which seems excessive.

Carl

 

I read the Datamaster as total timing. I know when I check the timing at idle to the balancer it reads total.

 

88GTASTK,

At WOT, what does datamaster say your maximum advance is?

With a custom chip, mine says 32 deg at 5200. I am not sure if want to bump up the total timing, if it is truly 38 deg (32 + 6 base)

Just took off my heads for a rework. Later, I'll have to see if I get the same thing that you got at idle.

Carl

 

Mine says 26 degrees @ WOT. I've backed out the timing tables.

There are some correction / offset things going on at different times that I'm not 100% sure of yet.

 

Your advance reading looks low to me.

Datamaster reads 29.9 deg at 4800 and up @ WOT on my car.

Comparing to my PROM tables, this value corresponds to

= main spark table (extended) + PE advance - retard for knock (=0)

If I add 6 degrees of initial to the reading, I get 35.9 deg, which is where I would expect to be. I suspect that the Datamaster does not give total advance on cars where initial advance can be set via the distibuter.

 

The base timing is already included in the main s/a table.You do have 29 total timing.

 

KVU,

Thanks. That means that there is probably more room to play with raising timing.

Carl