Lets go back to square one. I've had some good discussion and input from this collective wealth of knowledge on this irritating problem. I've made some changes/improvements but I still am not satisfied with the smoothness of this engines idle.
Back to the facts: 1966 289 2V, CA emissions heads, bored .030 over, Pertronix ignition, roller tip rockers, otherwise totally stock rebuild with original 2 into 1 exhaust. And the carb was "re engineered" by Pony Carbs. Transmission is a C4. I have about 500 miles on it at this point.
The problem: Idle shakes the car, not an intermittent shake, a constant one. As if it is misfiring. It seems to improve with the engine up to temp or a faster idle speed and/or more initial advance. If it's in gear with the A/C on (under load) it seems to smooth a little. Performance on the road is great, no hesitations, pulls strong, cruises smooth. Also there is one lifter that consistently ticks on startup but only briefly.
Things done to this point: Compression check, cold, no plugs in, carb wide open (good all up to 160-170 after 3 strokes). Vacuum reads a steady 18" at idle. Replaced stock rockers with roller tipped. Checked for low voltage effects on Pertronix module (none found). Checked for internal vac leaks with propane, no "smoking gun" found. Experiments with different initial timing, (Pony Carb method, no light, just adjust for max vac and smoothness, results in 40+ degrees initial advance! amazingly the thing actually runs well like this! The vac advance is detrimental here though. Duh!) (Recently re set by the light to initial 14 deg advance with carb adjustments back to 18" vac) seems more shaky under load now. And yes I've verified TDC on the balancer and even added a timing tape to measure more accurately and total advance.
Replaced 7mm plug wires with Pertronix 8mm. Added 40k volt coil.
So what am I missing here? All the vitals seem to indicate a good healthy engine. Does it need more break in time? Am I fighting a natural characteristic of a 289?
Back to the facts: 1966 289 2V, CA emissions heads, bored .030 over, Pertronix ignition, roller tip rockers, otherwise totally stock rebuild with original 2 into 1 exhaust. And the carb was "re engineered" by Pony Carbs. Transmission is a C4. I have about 500 miles on it at this point.
The problem: Idle shakes the car, not an intermittent shake, a constant one. As if it is misfiring. It seems to improve with the engine up to temp or a faster idle speed and/or more initial advance. If it's in gear with the A/C on (under load) it seems to smooth a little. Performance on the road is great, no hesitations, pulls strong, cruises smooth. Also there is one lifter that consistently ticks on startup but only briefly.
Things done to this point: Compression check, cold, no plugs in, carb wide open (good all up to 160-170 after 3 strokes). Vacuum reads a steady 18" at idle. Replaced stock rockers with roller tipped. Checked for low voltage effects on Pertronix module (none found). Checked for internal vac leaks with propane, no "smoking gun" found. Experiments with different initial timing, (Pony Carb method, no light, just adjust for max vac and smoothness, results in 40+ degrees initial advance! amazingly the thing actually runs well like this! The vac advance is detrimental here though. Duh!) (Recently re set by the light to initial 14 deg advance with carb adjustments back to 18" vac) seems more shaky under load now. And yes I've verified TDC on the balancer and even added a timing tape to measure more accurately and total advance.
Replaced 7mm plug wires with Pertronix 8mm. Added 40k volt coil.
So what am I missing here? All the vitals seem to indicate a good healthy engine. Does it need more break in time? Am I fighting a natural characteristic of a 289?
