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Q & A: Hot Running

John:

You may remember I am Willard Brown's brother and had my '67 MGB rebuilt last year by Peter McCarthey of Midnight Auto here in New Jersey. You were kind enough to be supportive when ever I had questions on the details of the engine rebuild.

I am a NAMGBR and have an additional question about engine temperature. From reading my MGB owners manual / shop guide I have learned that the operating temperature for an MGB engine should not be greater than 190F.

I am concerned because while operating my newly rebuilt engine at 65 - 70 mph the engine temperature has been in access of 190F. The temperature has gotten as high as 200F on short 45 mile highway run. This concerns me because the ambient temperature was only 72F. You may recall my mechanic suggested that the car would not require an oil cooler, so on reassembley no oil cooler was used. A new radiator, water pump, 160F thermostat, all the recommended insulation for the bonnet and around the radiator have been applied.

The rebuilt engine compression has been increased from 8:3:1 to 9:5:1. I have driven the car approximately 1400 miles.

Is it normal for the engine temperature to be 195F or 200F?

What can be done to correct this problem?

We have retard the fuel mixture and changed the timing, it has not help. It has been suggested to me that the engine needs 2000 miles to really break in and settle down and may run hot until then. Is that true? I do not want to burn up my rebuilt engine.

Do you have have any suggestions? Please reply as soon as possible, thank you.

Paul M. Brown

PAUL!

The newer gasoline seems to produce more heat than the old gasoline -- this may seem like an urban myth (perhaps it is), but many of the earlier MGs (with precise instrumentation) seem to run much hotter now than they... read more