66 Ford F250

put on a new fuel pump and filter. Just checked that spark. It had some orange in it. Was trying to start it before I changed the distributor cap and wires, and the muffler blew up. Now I have the new cap, wires, and plugs. I took off the head on one side to try and see if they were going up and down when I turned the motor they were thats when muffler blew.

Test the ignition coil sounds weak-also check the valve and ignition timing

rakkasans166,
Just a note about the blowing up of the muffler. Had a 1968 GMC Value Van w/fresh rebuilt engine. Could not figure out why it was backfiring, running like crap....also backfired so bad it blew up brand new muffler. About to give up when we took brand new cap off and looked at it in the sun, minor crack down inside. Could not see it in the dim light. That's all it was....Hope that may help. Don't overlook the simple things. Easy to do. :)