In this video Ray Bohacz explains how to diagnose and solve common problems associated with HEI ignition systems. These include marking the unit before dismantling, the care required during dismantling, checking the pick-up with an Ohmmeter, and examining the ignition module, which replaces the breakers by turning the coil on and off, and the remedy for overheating that causes intermittent spark.
A calm analytical brain and a manner that has won him many friends and viewers, Ray Bohacz is articulate and meticulous in his technical video presentations.
Watch and learn from Ray’s good advice.
New Jersey native Ray Bohacz is a respected engine builder. Though he relished the challenge of preparing race-winning engines, his earliest memories were linked to farming and its many aspects—particularly its mechanics. Recently he has combined these interests by demonstrating the value of short, technical trouble-solving videos.
My 1977 F350 with 351cid has always run rich and misfires in rainy weather. I changed the cap, rotor, wires and spark plugs but to no avail. Last time it rained, I tried changing the HEI module but still no joy. It started and ran fine and then I stopped it for a while. When I tried restarting, it backfired terribly. I discovered the distributer vacuum-advance mechanism was not working. I’m about to replace it but would like to identify the cause of my problem. Any ideas? Mike
In both Part 1 and 2 of my videos, I’m discussing the Delco General Motors HEI ignition, which is dissimilar to your system. From memory, your 1977 Ford 351 runs a Motorcraft Dura Spark I or II – most likely the latter. On a dry day when your truck is running fine, I suggest wetting the ignition system with a spray bottle, isolating one area at a time. The truck may have a cracked ignition coil. Let me know your findings, and if I can help further, please say. Good luck! Ray