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1964 Olds Cutlass with 1975-- 455 engine running HOT


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I replaced the stock 330 engine in my 1964  Olds.  Cutlass with a 1975 Oldsmobile 455 engine from a Delta 88-Royale. I installed a new water pump but used all the pulleys from my 330 engine onto the 455. I installed a 26" double pass aluminum radiator purchased from SPEEDWAY. In highway I am running about 200 degrees--in city it tries to climb as high as 230--UNACCEPTABLE.

     I WAS WONDERING IF MAYBE I NEED A high volume PUMP INSTEAD OF A STOCK WATER PUMP??? We kind of figure the issue seems to be water flow!!!

     Discharge temp is upward to the high  limits stated---but the bottom hose registers about 190 degrees. I can accept the fact my water temp gauge may  be inaccurate--but not by as much as indicated.

     I DO NOT have a fan shroud--haven't figured out how to build one for the engine fan and my modified radiator installation---BUT not sure the issue is the air flow any way.

     Anyone ever encounter an issue like this???I really need some suggestions before I just start changing things. The engine runs excellent--and does not spit out coolant from the overflow as expected with the indicated TEMPS.---SO it really puzzles me as to why the TEMP IS SO HIGH---ALSO THE TRANSMISSION COOLER IS SEPERATE FROM THE RADIATOR SO THAT IS NOT THE ISSUE.

         Any help will be VERY MUCH APPRECIATED.




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Throwing together mismatched parts is a great way to uncover problems, so please back up and tell us EXACTLY what your configuration is. Many "cooling" problems are really caused by incorrect ignition advance or incorrect jetting.


What cam? What intake? What carb? What distributor? What fan? With or without clutch?

Is the carb jetted for the application and today's ethanol-laced gasoline?

Is the vacuum advance running on ported or manifold vacuum?

Have you recurved the distributor advance or are you running the 1976 emissions advance curve?

Are you sure the thermostat is actually opening fully? Is it facing the right way (some t-stats have a preferred clocking orientation).


Also, I don't know anything about that Speedway radiator, but I am underwhelmed by "dual pass" or "triple pass" radiators.  The dual pass doesn't increase the surface area of the radiator, all it does is double the flow path length while cutting the total cross section area of the tubes in half.  Cutting the cross section area in half will cut the flow rate through the radiator in half  also, which pretty much negates any "high flow" water pump. Do you have a spring inside the lower radiator hose? The suction from this flow restriction could cause the lower hose to be sucked flat.


Do you have a 1964 style water pump (driver side inlet) or a 1965-up style water pump (passenger side inlet)?


As you know, the 1964-65 cars use a down-flow radiator. I assume this dual pass radiator is a cross flow. How did you install it in the core support?


Assuming the carb jetting and advance curves are correct, I'd get the largest single pass downflow radiator I could fit in the core support. Here's one option for a large aluminum radiator for the 64-65 cars that uses two rows of 1" tubes. Core dimensions are 17.25 x 25.5. Use a six blade thermal clutch fan and install a shroud. The 65s came from the factory with a big block 400, a copper radiator, didn't use a "high flow" water pump, and didn't overheat. 

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