Engine Misfiring
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Joined: Jun 2013
Posts: 87
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Engine Misfiring
I have a 1968 327/300 HP engine modified with a mild cam, Mallory electronic distributor, Holley Sniper EFI and chambered exhaust. The car has been running perfect for many years, but on my last ride after driving for about 45 minutes it started to breakup around 2 - 2,500 rpm. Dropping down to 1,500 rpm it ran well enough to get the car home. In the garage it still exhibited the breakup and I did a data log and sent it to Holly. They informed me that all aspects of the EFI were within the normal range but it was getting an inconsistent rpm signal and that was causing the problem. A few days later I started the car again and it reved to 3,500 rpm with no breakup (cold engine). I have not driven the car since. I agree it is most likely an electrical issue. Many years ago I had a similar issue,with a prior car, and the culprit was a coil breaking down with heat. I'd appreciate any other suggestions. Thanks.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Most likely the Opti-eye in the Mallory is not pulsing properly, or is this a magnetic Mallory? They made both.....but that is where I would start as the Sniper gets its signal from distributor pulse.
Jebby
Jebby
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Could be the Coil in the HEI is failing as well. Try cleaning the optics or the magnet that jebby mentioned, THere could be years of dust and crud from normal wear. if that doesnt work look at the coil
