There is a difference in solenoids, also the strength of the solenoid plunger return spring.GM issued a softer return spring to ease hot start problems. I use the blue streak #SS200 starter solenoid.
If the brushes in the starter are wearing out the starter can draw extra amps and cause problems. This usually makes the starter move rough and jerky before it quits entirely.
Make sure all cables and switches are good, especially the neutral safety switch if your car has one. They wear out due to the sliding each time the car is put into gear. Throw in some dust (like on our farm) and it wears out even quicker.
The add on solenoid deal works if you don't have a switch going bad or other starter problems.
So far, with every one of the hot start problems I've had, I have solved it by changing parts on the starter or correcting other problems on the car.
This is on a fleet of over 20 vehicles.
David
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Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
[This message has been edited by davidpozzi (edited 10-21-2001).]