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Engine failure when hot



I have a 79 automatic to which I installed a ZZ4 crate engine. The car rides great but I have a problem when the engine temperature gets close to 220 degrees. The GEN light lights up and the engine fails and sometime stops. It usually happens when running at 60 mph and more. First I taught it was the coil and changed it for a new one but it did it again!

Anyone as a clue about this? Recommendations are most welcomed.


The Gen light could be that your alternator is failing, just my guess. And running up to 220 is a little too hot I think, I'm in Florida where it's blazing hot all day, have a 383 stroker motor and it hasn't got over 180 yet even in the insanely slow traffic here (thanks to the blue hair geezers who should be riding the freakin' bus instead of smashing into everything), yes, I have issues with geezers :D :L


Do you have a fan shroud? What temp thermostat are you using? What is your'e rad cap rated at ? Could one of your'e rad hoses be collapsing? Have you flushed your cooling system? Is you're mixture of antifreeze more than50/50?

These are just some things you might want to check if you havn't already. But I aggree about checking the alternator. Is the belt tight enough as they do stretch quite a bit after being installed.

If all checks okay and you are runnung with a clutch fan you might think about a direct drive fan used for racing. ( not a flex fan ). We were running around 225-230 on the highway and made the above changes and dropped out temp to 200 on the highway which is not bad for a 454 in 90 degree weather. We are using a 7 pound rad cap now, 180 high flow thermostat, flushed system several times over a few day span, and most importantly replaced the fan shroud that the previous owner had removed. Also make sure you don't have an air lock in the cooling system!!!
We did the first time after changing the thermostat. If so you can do one of several things to get rid of the air.


Well-known member
Jul 3, 2001
Auburndale, Florida
1969 Killer Shark
We really need more details about your configuration (ignition/carb, etc).

My guess is that the igintion module in the distributor is failing. Most autoparts stores can test it for you. However, it may only open an internal connection at 220 degrees. So after it quits, you let it cool down and she will refire.

A new one is from $19 to $49 depending on where you buy it, and not a bad investment if yours is original.

As far as the temp goes, 220 really does not bother me, as the engine burns cleaner and is far more efficient at those temps. However, if you can get it to run cooler, I would suggest exploring that avenue. The problem with running 220 is you are just about 20 degrees away from total danger zone vs. being 40, 50 or more like most of us prefer to run.

There are dozens of ways to cool it down. You will appreciate that on the inside as well, because a cooler running engine means cooler toes, and less heat in your face.


I think you might also want to check your battery and ground cables. That "GEN" light is trying to tell you something.

Steve :w


My guess is you either have a bad ground ( acts up with heat ) or a bad alternator that also is breaking down as it gets hot. Try cleaning your grounds and make sure the connections are good. If that doesn't solve the problem then most likely you have a bad alternator.


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