starts and runs fine until it is up to operating temp, then for no reason won't turn over. lights and radio work and it doesn't happen every time either. I am able to do the screwdriver to the coil trick to get it running and then it seems like when it cools down , works fine again. please help, thanks

 

starter solenoid might be going bad. Also check the battery ground.

 

Is the timing set properly? I have my timing advanced pretty far on my K5 and it will turn over slow when trying to start it hot. But it always starts.

Is the starter original? Could be a weak starter.

 

Have the Battery checked.
My 86 was doing the same thing when I first got it fom my nephew. He said the battery was fairly new. brought into Shucks to test and sure enough it had a dead cell. Good news was I got a free replacement under warranty. Good luck.

 

An easy fix for this is to install an ignition interupt switch(kill switch).
Turn it off while cranking then switch on while cranking. It will cure the slugish start from to much timing.

 

That works. I used to use that on the old dirt track cars. I run 12.5-14:1 compression and one of the rules stated we had to use stock oem starters. We only had an ignition switch and starter button. With as much as 33-36degrees advance Oem starters didnt hold up long. Then a drag racer told me to spin the engine over then kick on the ignition. It does work. But the the guy posting the question here said it would start with a screwdriver on the solonoid. Doesnt that mean the battery and cables would be working ok cold or hot. My guess would be the small wire to the solonoid to might be loose or corroded.

 

thanks, I will check the little wire.