I have a 68 Camaro with a 396. The car runs good until the temperature goes up from low speed driving in hot weather. The car starts running rough and sometimes will shut down and I loose all electrical until it cools down. Any ideas on what's wrong? Would like to figure it out before the Power tour

 

How is the Alternator?

 

What do you mean lose all electrical? It acts like the battery is dead, or just the ignition goes dead?

 

It acts as if the battery is dead. No power at all. Tha alternator is a new 100 amp.

 

Sound to me like your losing ground.

 

What would make it loose ground when the temp goes up?

 

Do you have a volt meter? When it goes dead, do you still have voltage at the battery? Have you cleaned the battery terminals, power connection at the starter, the battery ground wire to the engine block, and the ground strap from the engine to frame?

 

I have checked everything except volt meter check.

 

How original is your under hood wiring? On the drivers side of the radiator core support is the voltage regulator (if the alternator hasn't been updated), and your horn relay. The horn relay is also a major junction block for power. Have you checked those for cleanliness too?
And don't ask me why it would make a difference when hot. Some things electrical don't always make sense.

 

I took it to a shop last summer and they changed the alternator to a 100 amp with the internal regulator and said that they checked all the wires under the hood.