1986 L98; I have the 7165 ECU. Stock AARL chip. I'm looking at Craig Moates software at idle; it says ~27* at 800rpm. TunerCat shows my chip is set at 20* at 800rpm. No problem; my static timing with EST disconnected should show ~7*, no?

So I hook up my induction timing light, clipped to #1 plug wire...And the damper hash mark is way up at 12 o'clock, nowhere near the timing tab...

The car runs good; I'm checking prior to making any changes in my chip...

Does this sound like a distributor that's one tooth off?

 

The ECM has no idea where your distributor is really set to. It's programmed to think the dissy is set to the factory spec on the emmissions label.

Fbodys are set to 6° initial with the EST disconected. Don't know about ybodys.

The value displayed on the scan tool does not reflect actual dissy position. If you twist the dissy to 15° initial the readout on the scan tool will remain the same.

I doubt you are "one tooth off". Perhaps the dampner ring has slipped, or the initial timing is way advanced. A piston stop and grease pencil will verify dampner accuracy in short order.

 

...Argh!!!...Every time I'm ready to burn a chip, something else comes up!!!...

The rubber does look "squeezed out" on one section of the damper...Feels solid, though...

Looking at my L98 alum head spark plug hole, how would I get a TDC indicator in there??? It almost looks like it's aimed 90* from piston...

(Darn! This is delaying me again; I have 180* thermostat, 200* fan switch, new hoses, all waiting for the new EPROM BIN, which is already burned...But how can I change BIN values with no reliable initial spark advance setting??? Argh!!!)

 

Better safe than sorry. Nothing like starting off with a faulty baseline.

I'm sure the piston stop will thread in far enough to contact the piston and hold it below TDC.

You might want to mark the dampner's hub and outer ring so you can tell if it slips in the future.