overheating race car - stumped!

[71Nissan240Z]

Diesel water pump. Is it better than the normal petrol pump.

[cbuczesk]

Lighter as in cleaner. Everything about the head gasket looks fine. I went over everything for a long time with a flashlight and magnifying lens. I checked the head with a straight edge and it looks good. Whew! I think I'll prep the other head and have this one checked by the machine shop.

Chuck

[madkaw]

What HG were you using? Do you run just water or Glycol ?

I asked about the cleaner pistons because maybe some water was steam cleaning your pistons . It wouldn't take much of anything to pressurize the coolant system.

[cbuczesk]

I used a full FelPro kit. I've never had a problem with FelPro. I ran water for the first weekend of use and a mix last time. I think there was a little steam cleaning the pistons and chambers. I think it was a very small leak and the temp dropped to normal under normal loads. When I did easy laps and the cool down lap the temp dropped to normal. But after 2-3 hard laps it was 240 degrees.

Chuck

[Zed Head]

Any chance the head had some warpage? Was it machined to flatness before building, or maybe at the high end of the warp limits and used as-is?

I've never rebuilt an engine but I'm curious. I have a warped head in the garage and wonder how much is too much and what the effects are.

[madkaw]

Just curious of your engine specs as far as CR?

[cbuczesk]

The head was on an engine that I removed from a car about 20 years ago. I had the head resurfaced just to clean it and make sure it's straight. We aren't allowed to shave it to raise compression for IT racing. I have new 20 over pistons installed so compression is about 9:1...stock. Everything is stock except for +20 pistons, Hooker header, exhaust, semi-custom air cleaner, oil cooler, Taylor plug wires and MSD 6.

Chuck

[madkaw]

Personally I would spend the money on a Nismo gasket. They are pricey, but I think it's worth it. 125$ at Courtesy Nissan.

Edited July 20, 2013 by madkaw