i have a 1977 350 olds motor that i had rebuilt and bored over .30, i put a elderbrock performer rpm package on it with the alum. heads,cam the usual stuff when u redo a motor. long story short i can cruise around town but when i decide to get on the highway it starts to overheat. got a 3 row radiator from autozone, flex fan didnt have a shroud, changed thermostats, carquest stock waterpump,even ran it without the stat, spring in bottom hose. still overheating any suggestions i would grately appreciate it. mike

 

Had same issue with my 1969 350 and did the same stuff as you. I added a electric fan and problem was solved. now I run between 170-180 degrees.

 

The fan has virtually no affect at highway speeds. That's why cars come with clutch fans. If the car is cool at idle but overheats at highway speeds, look at radiator size, internal blockage, collapsing hoses, sludge in the block, or something that's preventing coolant flow.

 

Lean mixture or improper timing can cause overheating at speed, too.

 

installing a electric fan and new water pump this wkend. i thought about changing to an aluminum rad but i figure the 3row from autozone was sufficient enough. i guess i find out this wkend. thanks for the feed back mike

 

Glad to have you with us here and hope you can fix your overheating problem.