[MT-2500]

Originally Posted by pwrbydeere

I've got a 454 that overheats while driving. Idling in heavy traffic on a 100 degree day is no problem, it runs at whatever the thermostat is. But get on the road and it will boil within 20 miles, no matter what temperature it is outside. It's a gen 5 454, I believe a 1993, in a 1971 chevy K20. Currently has a brand new heavy duty 4 core radiator, dual electric fans, highflow iron waterpump and a 160 degree thermostat. When I got the pickup it had a 3 row questionable radiator, a stock pump, a stock flexfan and a 195 thermostat. All these changes didn't help it a bit. I had thought that maybe the waterpump was a reverse rotation, spinning backwards (it has v-belts), the new highflow pump didn't help. Thermostats only change it's idling temp. It has stock '93 heads with what I call peanut ports (small) and a 60's era cast iron highrise GM 4bbl intake. The ports don't really match up. I don't know why this would affect heating though. It had a stock lowrise 4bbl manifold when I bought it. I have switched distributors, and had timing at every imaginable degree. No change. It had a 4150 Holley, now a 750 Edelbrock, no change. I have rejetted many times. I have double checked temps with other gauges and my infared thermometer. It runs great, good power. This engine has only 3500 miles on a complete rebuild. I found out that this engine was formerly in a 1947 chevy coe carhauler. It overheated for that guy too. He even plumbed 2 radiators to it. It was yanked out and replaced. A guy bought this engine, had it completely rebuilt and installed it in this K20, then I bought it. I'm out of suggestions. Any help would be appreciated.

You may want to check base time.
Does the heater quit working the same time it heats up ?
But if all else fails run or have a repair shop run a chemical /block/head gasket check on it.
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