Hard to start after warming up

After my truck warms up (1973-302) it is very hard to start. It drags like the battery is dead. I've adjusted the timing, and when adjusted correctly is very hard to start. I end up turning it back a few degrees to help it spin over a little faster. My battery is new, just replaced the alternator. I checked my alternator by unhooking the battery while the truck was running and the truck died. Put on another alternator (spare, not new) it will now run with the battery unhooked.
My voltage gauge just bounces all over, hard to tell what its charging to. If I let the truck cool a little while, it cranks right over fast. What can cause this?

Jim

Jim,
First, dont ever take the battery cable off while the engine is running, it actually tells you nothing about the alternator, and does extensive damge to the alternator's diodes. I would think at this point yu need another new alternator, and this time check it with amp guage.

Your hard starting problem is mostly a worn out starter. Possible bad wiring, but about 90% of the time it is the starter. But dont forget to replace the solenoid on the fender as well.

Thanks Ray, I'll give those a try.

Check your grounds they are usually the biggest cause of problems.

It's the starter. The motor is always harder to start when hot. If it were a built up 347 or 351w I would say get a high torque starter. If you get a stock one get a decent one from Napa. The cheap lifetime warranty ones from the cheap auto parts stores don't last very long. Sure they replace it free(if you can find the receipt), but who wants to change their starter every year.

Sounds like worn out starter. Mine did the same thing when it got a little warm!