Originally Posted by Crash!

Plugs were getting blown out on the old NON-PI heads, specifically on the Lightning. Under boost, the plugs were pulling the threads out of the heads. In 97, 98, and early production 99 heads, they only had 4 threads. From late 99 until the 3-valve came out, the PI heads have 8.

That doesn't mean the torque spec doubled. We are still dealing with aluminum heads.