This Week At

by Cara Barrett on August 5, 2011

This week I got a call and an email from a ’67 GTO owner from Ohio. Here is his email:


I rebuilt my motor on my 1967 GTO.  The motor is a 400HO.  I cannot seem to keep the water temp under 210.  I have new 4 core radiator, 180 degree thermostat, fan shroud w/a 7 blade fan and new thermal clutch.  Is this an okay water temp?

Thank you,

Roger Maggert

Roger also called me and we discussed his problem in depth. Initially we discussed his current compression (11:1) and him using regular fuel with an additive. My suggestion was to try and use some race gas, which will put enough lead back in the combustion chamber that this may help. I also suggested to go to a 160 degree thermostat to see if that made any difference. It seems that lots of Pontiacs seem to run hotter (most over 220 degrees) than the Chevy’s I have built and ran over the years.

After having time to sleep on it, I also believe the GTO temperature sending unit is placed either in the head or the intake. This is where it’s reading from & it’s obviously pretty hot there. I would also suggest getting an infrared laser thermometer & check the cooling system for hot & cold spots. It just might be that the heat being sensed is partially from another source or possible blockage, even though the engine has been recently rebuilt by Roger.

Another thing to double check is to make sure the correct timing is dialed in and to check what water pump the car is running. There are 2 types of replacement water pumps, those with stamped impellers, and those that are cast. The cast impeller pumps cool better than the stamped. It may be advantageous to find the cast impeller pump. Let me know what works Roger!

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