[Grady Clay]

Jeff,

I was just about to write about the subject Philippe brings up.

First I want to hear about the condition of the pistons (specifically the ring lands) and the rings. Next, there should be some very careful examination of the rod bearings. You are looking for any hint of ‘spider web’ like cracks in the ‘copper’ layer under the ‘babbet’ bearing material. You probably will need a 10X microscope and look at an angle. The place to look is in the center of the bearing shell closest from the piston. The problem is the soft bearing material can mask the fractured harder ‘copper’ material. Is the bearing darker in that area?

Please tell us more about the engine configuration; type of piston, measured CR, cams, twin plug, sparkplug type, etc. What do the sparkplugs look like? What was your cranking compression? What fuel were you using? Octane? Did you have a head temperature reading? What was the weather that day?

How was the torque on all the head nuts? How are the other five head gaskets?



You say the mixture was too lean and there was detonation. Yes, there was the contemporary change in exhaust but what is the evidence of too lean and detonation (aside from a blown head gasket)?

I’m concerned you only focus on mixture and detonation and not investigate all possible causes. In fact there may be the confluence of multiple causes.

I think it unusual that the gasket failure is on the side. Most failures are just below the exhaust valve.



I have a similar setup in my ‘street’ 914-6; 2808 cc with 92 mm RSR Mahle Nikasil, 11.5:1 CR, S-cams, 2.4S MFI modified for proper mixture, 112 octane VP race gas, etc. I would regularly change from my original, stock 914-6 muffler to a Bursch 2-into-1 straight pipe. Yes it would lean slightly but never enough to be an issue. With either exhaust I had a nice light gray tail pipe and good looking plugs (NGK BP8ES or BP9ES depending on conditions).

One thing I do differently is use the “Rubbermaid Solution” with water into the cooling fan. This tends to keep the heads and cylinders much cooler that just air and huge oil coolers.


Jeff, I am very sorry to see this and I feel for you. Let’s make sure it is not likely to happen again.

Best,
Grady