thermostat housing problem

[n4ue]

Hello to all. I would like to share a near-disaster that happened to my SB Superformance this weekend........

My car has a 392" Ford Crate engine with a Speed Demon and complete MSD ignition system. It runs very nicely and has a whopping 650 miles on it. I did the motor install using a Superformance install kit. The wife and I took it for a cruise, and she noticed that we were running on fumes, so we pulled into a BP near home for some $2.27 / gal 93 octane......

As I was returning to the car, I noticed fluid dripping out the bottom. It was anti-freeze. Opened the hood and it was really leaking from the thermostat housing, where it mates to the Victor manifold. I packed the area with paper towels and returned home, keeping an eye on the temp guage. (I installed a fan over-ride switch and this really helps cool the car)......It never got hot.

After it cooled, I disassembled it to find out what was wrong. The root cause was a poor fit of the thermo gasket to the manifold. The gasket has 4 holes:
1, a biggie for the thermo
2, 2 small oval holes for the mounting bolts
3, a hole about 7/8" for the bypass

The bypass hole in this gasket is waaaay too big. The bypass opening in the manifold and expansion tank / thermostat housing is about 7/16". Looking at the crushed area of the gasket, revealed that there was about only .005" of gasket captured on the outside of the bypass hole, on the manifold side. Since it was 95 degrees, I guess there was enough pressure to push out this gasket and the result was a loss of coolant. Big time!

Today, I went to NAPA and bought a new thermo and gasket. The ONLY SB Ford gasket they had was EXACTLY the same! The new gasket and the original even have the same P/N......33633. I bought a sheet of gasket material and was prepared to make a gasket with the smaller hole for the bypass. On the way home, I stopped at Advance. Same thing, bypass hole too large. I explained to the counter guy what the problem was and as I was walking out, he called me. He had gone back and looked through the gaskets and found one that was a perfect match. It's Advance P/N85721, made by Engine Seal.

Now, I'm not saying that this could be a wide spread problem, but I strongly recommend that anyone with a Superformance SB, check that gasket. It's easy to change and it's the best $1 that I ever spent!

Have FUN!!!!

ron