M38 Engine

[jimbob]

I have a m38 that runs hot when driven above 45 or 50 MPH. Engine has been bored 0.80 thousand. I think this may be the problem. Has anyone else had this problem.
Would it help if I had sleeves installed and put engine back to std. bore?
Jim

[TomM]

Did you rebuild recently? Did it ever not overheat? I have a GPW engine bored .080. It did have overheating problems when first assembled and always at higher speeds especially on hotter days. During the rebuild it recieved a rebuilt water pump and new T-stat.
The manual specs .040 max bore so I had the same concern you did.

Before jumping to a conclusion check timing and tune, cooling system health including fan, water pump, T'stat, clean block, shroud is in place on the radiator, hoses, coolant level, accuracy of gauges.
Did you recently rebuild the engine? Did it overheat before?

Solution: radiator flow was restricted after 60 years of use. A flow test was done by a local radiator shop who works on old brass/copper radiators. It was recored and since (now 10 years) then has never shown any changes in temp and runs strong.
It had never overheated before the bore/rebuild because it was in such rough shape that it didnt go 40MPH.

The .080 has not been a problem in my engine. You dont want to jump to a conclusion to rebuild/sleeve the engine and address the same symptom afterward. Systematically eliminate as many other possibilities

[jimbob]

Tom,

I had engine rebuilt, also new radiator, water pump and thermostat . Engine has about 1,000 miles on it now. If I drive it slow 30-35 mph it does ok and if weather is cool it does ok. I have tested temp gauge it is ok. also changed thermostat. thanks for your reply.

Jim