Join Date: Apr 2014
Location: Sunman, Indiana
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1966 Ignition and Cam Timing Issue
I have a 66 with a tri-power set-up on a 389 that was rebuilt in 1990 and finally started for the first time last week (yes - a 24 year project). Cam is not factory (Cam Dynamics), installed by previous owner. It has 0.437 lift and duration of 224 at 0.050, so by my understanding, this is not too aggressive. Engine is bored 0.090 over. All else is largely factory.
Adjusted outer carb linkage to eliminate vacuum leakage. Finally got engine to idle at 750 rpm, but idle timing HAS to be in the range of 25 BTDC and seems to like 30 even better. Will not stay running at anything below 25 unless idle is cranked up. There is an inconsistent and somewhat deep knocking sound, which I suspect to be pre-ignition at idle. Engine revs and sound fine at higher revs. At idle, the engine runs consistently, but constantly shaking (not terribly bad, but certainly not smooth). Total timing is about 40-45 BTDC at 1800 rpm. Vaccum advance is disconnected and plugged for all of the above.
Could valve timing being off by a tooth? I hate to pull this nicely finished engine apart to check since I doubt it's wrong, but I don't know what else would cause such advanced ignition timing. Any idea's and other thoughts?
Side note - Interior is not installed, so car has not been driven on the road to see how it behaves. If it wasn't for the overly advanced timing and slightly rough idle, I wouldn't think anything was wrong at this point.