[72step]

I have been experiencing an intermittent miss-fire on my truck which I don't drive a whole lot. The truck has a high Perf 327 with about 4k miles since being rebuilt about 14 years ago. In the last two years I've replaced the carb with a new Quickfuel dual feed, I've replaced the plugs, and wires. The last time I messed with it earlier this year it would seem to help to mess with the dist. cap but I'm not sure it really changed anything. I started it up 2 weekends ago after about 6 months of sitting and it sounded like it was ready for the drag strip. Then last weekend I started it and moved it around to do some other stuff to it and it sounded good with a very minor hint of a miss. Then today I pulled it out again to work on some more odds and ends and it sounded horrible. Back firing with barely enough power to move around my property. I'm just trying to figure out what it could be. I suspect the ignition system which is a Mallory Unilite with a promaster coil. My second guess is a loose wire or bad ground somewhere. My third and more dreaded guess would be a flat cam? I appreciate any advice yall can offer to try and pinpoint this. Could it just be bad gas? Thanks....

It has a Comp Cams 280H hyd cam, roller rockers, SS valves chrome moly push rods, 9.5:1 comp ratio. geardriven-pretty stout engine and has always ran solid with no problems or smoke or anything like that.