Well, my helpful mechanic neighbour figured out why my MLS head gasket failed. One of the coolant passages in the block is corroded to the point that the edge of the hole is under the sealing ring on the MLS gasket, so it took only 10,000kms for the coolant to get past the gasket.

Before I took the head off, I tested all the head bolts by checking how much torque to took to move them (to tighten them). The bolt directly beside the dodgy coolant passage was 40 lb/ft less than all the rest. I initially thought that the loose bolt was the cause of the failure, but it is more likely the symptom. The bolt is looser probably because of the coolant getting between the block and head there.

The correct way to fix the coolant passage is to replace the block. But I can't be bothered doing a complete swap on a freshly rebuilt bottom end. And using another MLS gasket on the existing block will just cause the same problem a few months down the road. But a quality graphite gasket will seal the coolant passage just fine. It might last only 150,000-200,000 kms, but that's about 10 years - which is enough for me.

My problem is that a normal graphite gasket is 1.30mm vs the 0.65mm of the MLS, reducing my compression ratio from 10.20 (with my newly skimmed head) to 10.03 - a drop of .17. That's not the end of the world, and I can live with it. But is anyone aware of a graphite head gasket less than 1.3mm/.051in thick?

Permaseal shows two non-MLS gaskets for the E-Series six: BR522 and BR522GP "Performance" Head Gasket. Does anyone know what the difference is? I believe they are both 1.30mm.

Thanks for the help.

High

I’m not sure of the part number but my build has a .035” graphite head gasket. I have .032” piston to head clearance, I studied and came up with the conclusion this helps with staying of detonation with a tight quench