The Racetractor. The End.

[Dave]

That head is perfectly fine you know mate, they crack and get to a point but dont really get any worse. I've had same head for years with these issues. You will eventually have a pre-cup fall out with lots of power as darren did, mine have started working out too, but it will always happen with more power.
Pushing 220hp it will happen on a brand new head.

Also, you'll get exactly the same issue with a brand new head due to the power/combustion pressures through the orifice, you cant get away from it on these IDI's, I just opened mine up a tad to release it abit more.