Hey guys: Hopefully I can ease this one in here...I have a vehicle that was originally Lean Burn equipped. I had all the hard parts on hand to convert it to an HEI, so I did. Since then, I've had ongoing issues getting it to run and to run right. It worked fine when I got it together. About 500 miles later, it lost spark after sitting about 4 hours. Tow home, try it several times and an hour later it starts and runs fine and hasn't repeated that episode just using it around the house. Yesterday I decided to replace the junkyard coil and pickup coil(in the distributor) with good quality new stuff I had. Took it for a drive today on my 5 mile test loop and picked up a misfire under load about halfway through which got worse the further I went. Felt like ALL the spark was randomly falling out, not just one cylinder. Further testing at home revealed that the misfire goes away when the engine cools down. Plugs, wires, cap, rotor are all recent and in good shape. Timing is 8 degrees BTDC with advance unhooked and mark is rock-steady. Pickup coil air-gap is set to .008 per the FSM. I want to post my setup in case I have done something glaringly wrong to cause this: 1979 318 vacuum distributor with new pickup and vacuum advance . Wells HEI module mounted on the passenger inner fender, on a heat sink and grounded to the chassis. Ford TFI coil mounted on the inner fender also and connected to the distributor with a good-quality 8mm 36" coil wire. The HEI module and TFI coil are both powered through a Ford cooling fan relay from a Crown Vic. The trigger for the relay was tapped off the key-on power to the original LB system, and the 12v run circuit for the relay is powered by another, separate 12V "battery voltage" circuit with a 30A fuse inline. Feel free to suggest improvements or point out something I did wrong. Thanks!