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Re: 56 DeSoto Fireflite Spark Advance Curve

From: Steve in KY
Remote Name:
Date: October 01, 2003


Hmmmmm, this is not a nitro burning drag car, it is a DeSoto!!!! Please review my thinking here and tell me if you concur, or if I'm out in left field. The vacuum gives max advance at high vacuum/low throttle opening while the mechanical advance give max advance at high RPM ie 4400 and above. So the 2 sort of counteract each other. The only time the adance should get anywhere near 40 is at high RPM when you take your foot off the throttle. At low rpm with the throttle wide open, there should be minimum vacuum and mechanical advance. OK, so the problem is that when set at 4BTDC or even TDC at Idle, I goose the throttle and get 40+ degrees of advance. It was accelerating very hesitantly and missing heavily due to detonation. Thanks god I didn't drive it far. When I unhooked the vacuum and set it at TDC at idle, the car accelerated briskly (tar' smokin') and smoothly. But that only gives me 20 degrees peak advance and it hesitates at high RPM. I will take your advice and try some new springs. I think I also have a new vacuum unit here somewhere. Thanks Steve


Last changed: July 19, 2018