This is a 455 oldsmobile motor,here is the story.This is a race motor,I start it up and in a few min. it builds pressure on the water hoses,then make a pass and temp goes from 160 to 220 in 1/8th,just started this about a month ago.No tstat just restrictor,I have flushed system,changed pump,cleaned rad.,pulled intake and heads,cked head gaskets and found no cracks in heads or intake also changed intake or blown gaskets.So anyone have any ideals

My old race engine had the same problem. I use an electric fan and aluminum radiator. Started using "Purple Ice" mixed in the antifreeze and lowered the temparature about 20 degrees. My new blueprinted motor had the friction coating done to all of the pistons - now it is hard for me to get to 180 degrees in the quarter mile. I too use restrictors and no theromstat. My compression went from 11/1 to 13.5 with the new engine and its running cooler. The friction coating on the pistons really helps. Sounds like you checked everything. Try the "Purple Ice." You only need to put two bottles in your radiator.

how about your radiator cap?

change rad. cap and same,so just changed from 16lb. to 13 lb. cap.also going to flush again and add something like that purple ice made by red line products.Thanks for the help,I will see what happens at the track tonite if it don't rain.

The only thing raising the pressure on the cap will do is raise the boiling point of the water in the system.I think for every pound of pressure you raise the system you raise the boiling point 2 degrees.

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71 RS split bumper with 383 & turbo 350

Took car out sunday and temp and pressure back to normal,don't know maybe leaking head gasket.