Spark Plugs Keep Going Bad
I have 302 V8 from a 1985 Lincoln Continental that I have dropped into a 1949 Ford F1 that I am restoring. The engine was rebuilt at a local machine shop. Here are the engine specifics:
Cylinders bored 0.040 over
New stock pistons
Stock heads with 120lb valve springs
CompCams Thumpr Roller Cam with 0.531 lift intake, 0.515 lift exhaust
Funnelweb 7-1/2" rise intake
600cfm Holley carburetor
HEI 50K Coil Disributor
I originally began with stock Autolite plugs. I start the truck occasionally to move out of the shop or a quick trip around the block. I haven't put it on the street yet. It began popping and backfiring on one cylinder and spread to 2-3 more cylinders. I tested everything I knew to test and finally bought a new set of Iridium plugs which cured the problem. However, a couple months later the problem started again. It got so bad the truck won't start now. I pulled the plugs and cleaned them but that didn't help. I pulled the coil, ignition module & pickup coil from the distributor and had them tested at the auto parts store. All checked out OK. I have since put new Accel wires on, tried a new coil in my distributor and finally bought a new distributor which is installed now. If I test a plug straight from the distributor I am not getting a spark. The plugs are gapped at 0.045. I tried one of my old Autolite plugs and I am getting a weak spark. I know if I buy a new set of plugs my problem will be cured once again for a short while. Since I have had 3 different new coils installed, I know it's not the coil, besides I have a new distributor in now. What is causing my plugs to go bad?
Thanks for your help......