Hello, Here's my problem if you could help please, 454/4sp, stock chevy HEI ignition. FIRST, it would consistently breakup around 5600 to 5800 rpm's. ? Today we went for a cruise and gently coming off a stop, ( after driving for 1.5 hours) I encountered a severe breakup at 3000rpm's. I revved it up again and noticed at the breakup point (3g's) the tach would fall off to 0. I repeated this 2-3 times with the same results. (it would run under 3g just fine). We pulled off and shut it off of course. It would not fire-up, spit, sputter, nothing but crank over. I thought maybe the rotor contact had shifted or a broken pin it the drive gear. No sir. Everything LOOKED fine. I jiggled a few wires in the distributor and nothing seemed loose or disconnected. So I put it back together (the cap & rotor) tried it again, it fired right up, so I took it home 1.5 hrs. the other way. It ran just fine, no breakup over 3000rpm's. Got it home ,shut it off and it just will not fire. After sitting in the driveway for three hrs., I went to put it away and it fired right up again. Can you help? :cool:

Sounds like a coil going bad alot of times they will act up when they get hot and will work when they cool down,that's just my guess!

I'm assuming you have a good connection to the B+ input and a full 12 volts on it when starting.

Had a HEI module act up. Car would run for days, then decide not to start, then start when it was good and ready. Problem was an intermittent GM HEI module. The removed 15 year old module tested good. I wasn't sure I nailed the problem until running the car for about 2 weeks without a problem. If you change the module buy a GM and use dielectric grease. Never had good results with the aftermaket modules.

Thanks so far, I replaced the module with after market (standard, Lee Auto parts). It back fired so bad on the test run the Flomasters exploded. I changed the coil and the same thing happens. I have a direct hook-up from the B+ to the battery, 13.8v, so the meter reads. Can the condenser be causing this or a short somewhere where the small two wires plug into the vacuum advance side of the module :rolleyes:

Check for continuity thru the the pick up coil. While checking wiggle the wires to see if it has an affect on the reading. This part rotates and the wires can break down over time causing an intermittant problem prior to a complete failure.