51 Straight 8 overheating problem

Posted by Classicdoug On 2023/5/2 15:24:05

I am restoring a 51 Packard Henney hearse for a customer. I inherited this project from another shop and have it reassembled. It is a decently low mileage car with what appears to be the original 327 engine. The current owner bought it at a car show but never drove it. It obviously drove because it was at a car show, but don't know any history.

We took the engine out, cleaned it, painted it, and put all new gaskets. The inside of the engine was very clean. The water distribution tube looks new. We installed a new water pump and everything else new as needed. We installed it and it fired right up. We ran it watching oil pressure, which is good, and the temp. The temp kept climbing and we turned it off when it hit 200. Since then we've tried everything we can think of to fix this problem.

We changed the water pump again, tried a different thermostat, took out the thermostat, had the head surfaced, checked the water distribution tube, put in a very large aluminum radiator, added an electric fan in front of the radiator, built a fan shroud for the mechanical fan, checked timing, richened the fuel mixture, etc. Nothing seems to help. Within about 10 minutes of running, it hits 200 degrees. We can see water running in the radiator so we know coolant is circulating very good. It just won't stay cool. Funny thing is even at 200 you can reach in, turn the key, and it starts and idles like a sewing machine. It even shuts off perfectly. It doesn't act hot at all. I'm out of ideas. Even my engine builder who's done many straight 8's doesn't have an answer. Any idea where to go from here?