Years ago I had my 1965 327/365 engine rebuilt. I spun a bearing. That's what happens when you drain the oil and replace the filter but don't refill the oil in the same day. Yeah, the memory doesn't get better with age. The shop said they shot peened the pistons to expand the skirts and replaced the bearings and rings. After that the engine would run cool as long as you were moving, but let it idle and the temp would climb quickly and boil over. No changes to the radiator, probably the same water pump, but I did change cams. I never figured out what was wrong, I sold the problem. Any ideas? Now I've bought a Ralley 350 Olds with the same problem. Tried different radiators, fans and shrouds no effect. This engine seems to have a very radical cam (loop and no vacumn at idea, probable the W31. Can a cam effect cooling as I describe?

 

Timing can!!! When was the engine last rebuilt?? Start with the basics, check tune, radiator flow, etc ...

 

If there is a fan clutch, make sure it is engaging. There will be a distinct roaring sound and a lot of air movement when it is engaged.

 

What exactly do you mean by overheating? Is the pressure cap lifting? What is the temp gauge saying? Are you sure the gauge is correct? Are your hoses collapsing? Just some things to consider...

 

Aftermarket water temp guage. Upon idleing for 5-10 minutes it will spew, but never a problem while running, ~180. It came with electric twin fans, tried clutch fan, even tried 2 other radiators. No difference. I think it must be internal to the engine. The Corvette was rebuilt and ran great. The Olds I have no idea except it seems to have a wild cam. Lopes at idle and no vacuumn at low rpms. The Corvette cam was degreed in and I always wondered about that. I hoped someone on here would have solved a problem like this before.

 

Is your pressure cap good? What temp does it lift at...180 is good while driving.