I was getting ready to remove my headers to send them off for coating but decided to do one more timing check to make sure the timing was synced up on the Ramjet 502 so I don't burn the headers up when they get back.
I'm running the engine with a Holley Commander 950 PRO ECU without the GM Spark Control Module and knock sensor wired up. So the ECU is controlling the distributor directly. The COMP double roller timing chain and GM distributor are brand new as is the MSD coil. Cranking ignition timing advance is set at 15 degrees and 18 degrees at idle in the spark map.
With the engine running and timing light hooked up the timing is wandering quite a bit. It's so bad I can't really tell where it is, but it's somewhere between 10 and 20 degrees I think. The engine idles a little rough with the cam I'm using, especially before it warms up because it's running open-loop under 120 degrees and runs on the rich side. But I believe the timing is set at the same at all RPMs I achieve at idle and a wide range of MAP signal. The next step is 20 degrees but I don't think I get to that RPM at idle. Warm idle is about 850-900 and cold idle starts at 1100, slowly dropping with temperature. It seems like no matter what the RPM does, the ignition timing should be steady when idling.
I don't know if the problem is the ECU, the distributor, or my timing light. I'm running the engine off of a different battery than the timing light, but both batteries are grounded to the engine. This is just for convenience, nothing else. The alternator is not hooked up but I have a charger on the battery. The timing light seems to be functioning correctly or at least it fires repeatedly like its supposed to.
I don't recall it doing this when I checked timing after firing it up for the first time, but maybe it did and I didn't notice it. It's a little hard to see the timing mark down there.
What's the most likely cause? Is there anything else I should be looking at?
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