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Wed Jul 02, 2003 8:46 am

I have just finished putting rings on a H block motor. Compression tested at 130psi. The motor turns over immediately. As soon as I drive it more than 10 minutes I start losing power and the motor is completely overheated. I checked the oil cooler. Even though its not a dog house cooler I figured it should still stay cool enough. The fins have been removed from the fan housing. The motor is exposed (BAJA) but I have put extra tin around so the heads would get a good flow of air. I think it must be internal but I have never heard of this problem except for poor air circulation. Any suggestions would help. With the new rings being put on a old motor have anything to do with it?

Wed Jul 02, 2003 10:58 am

The first things to check would be timing and airflow. Make sure that hot air from under the engine isn't being recirculated into the fan. You've got to have the bottom/top separated. The fins from the fan housing are important, especially if you're trying to run a non-doghouse setup. They direct airflow where it needs to go.

I would recommend going with the doghouse setup with the tin intact (within reason considering the exposed engine thing). The oil cooler cools the engine as much as (or maybe more than) the air. Between having the smaller surface area exposed to the airflow and the airflow being undirected, your cooling power is probably pretty minimal. I think your engine could make it with one or the other, but not both.

That's my (not-very-educated) guess, anyway...

Wed Jul 02, 2003 11:38 am

Mity, check your plug wires and timing.
I know, you already did, but check again.
I had exactly the same symptoms you describe when I rebuilt my engine. I pulled and reinstalled that engine 3 times, changed the oil twice, even tore it back to longblock and replaced the oil cooler, but it still overheated in minutes. After pulling my hair out for a month, I rechecked my plug wires and timing for about the 50th time. Discovered my timing was WAY off! (But I thought it was OK the first 49 times I checked it.) Fixed that, and a couple minutes carb tuning, no problems since.

Wed Jul 02, 2003 12:24 pm

there is an oil relief in the bottom of the engine you might want to pull it out and make sure its not stuck.

Wed Jul 02, 2003 1:07 pm

you might want to check your valves(too tight). I had a friend by a fastback that the owner thought the engine was blown. After ten minutes the engine would lose all power. We loosened up the valves and all better.

Wed Jul 02, 2003 5:29 pm

Thankyou all who replied, it will give me a start and the motivation to put the motor back in and get it cool again.

Fri Jul 04, 2003 8:53 am

Put the fins back in the fan housing.