I got around to checking the timing with a light, it was low so that mostly took care of the sluggishness. The idle misfire was worse though. I found the tiniest of vacuum leaks at the intake gasket so I ordered a Remflex to fix it. In the meantime I figured out that the distributor shaft bushing was worn, allowing the points gap to vary quite a bit so I hoped that would solve the misfire, but swapping in a better used distributor barely helped.
I ordered a new small cap HEI distributor, I wanted to be able to tune the advance curve but it wouldn't drop in all the way when I tried to install it. I noticed metal shavings on the cam gear, and matching scars on the distributor body. The stock distributor has a chamfer machined into the body to clear the cam gear, the new one didn't so I sent it back. I'll get a stock 70's HEI to replace it.
I took the manifold off last weekend to swap gaskets and found the source of the misfire... conditions in the head aren't the best for valve sealing. It has all the symtoms of burnt valves- misfire, lack of power, bad fuel mileage without the burnt part. I'm guessing the neighbor that took the truck to get it running must've left the intake open while he had it. There is no smoke or blowby so I'm optimistic that the cylinders and rings are ok. I've pulled a spare head out of storage to take to the machine shop to be skimmed and rebuilt with bigger valves and better springs, and I'll do some porting and add a lump port kit to help flow while its apart. He has a cam grinder so I'll take my extra cam and see what he can do with it.
The misfire isn't bad enough to not drive it, so it's up to about 500 miles on it now. The brakes seem to be holding a slight amount of pressure once they get some heat into them, and I've made sure the pushrod from the pedal isn't adjusted too far out so I have some investigating to do there. I'm guessing it's something inside the M/C, which I need to swap to a dual unit anyway.
