[MeanGreen1LE]

I decided to do a leak down test before pulling the head to attempt to diagnose my oil issue. You may notice in the picture that I did not test #1, it has minor thread issues and did not want to seal. However all the others were about 5% or less leakage. While this is the first time I’ve done this I pretty strongly believe that is pretty good, especially cold. To me this is yet another reason that points to something besides the rings. The way I understand it is the only way it could be the rings with leakdown that are messed up or improperly butted oil control rings?

So anyhow I proceeded to begin the process to pull the Passenger side head. This went relatively smoothly and I was pleased to discover that I was able to get to the head without removing the water pump.

I had bought some split ball hole gauges to try and see what I could figure out on my own before taking the head somewhere as I want to know what the deal is so badly. I hate the subjectivity of the split ball gauge and wish I had a dial bore gauge that small. I have a mitutoyo that goes down to .7” and that thing is great! I got super repeatable measurements when I was checking the tolerance of my lifter bores to lifters. It’s just so hard to know what the correct drag is when checking.

Thus far I have only checked the intake and exhaust on the problem #6 cylinder. It looks like on the intake where the top portion of the guide is at least close to out of spec, (.0024) and interestingly the intake and exhaust seem to have pretty close tolerances. See pics.

But!!! Here is the crazy thing I discovered. While micing my valves I very consistently was getting .3110” and a couple .3109” It hit me like a ton of bricks while I was averaging all my measurements that .3110 is not an 8mm valve. 8mm is about .315” and I did some reading and the valves themselves typically run about .313X. 5/16 equals .3125 AND many 5/16 valves are .311.

So I ran an 8mm flycutting tool in a guide reamed for a 5/16 valve! Ugh! I feel so stupid. I’ve mentioned that it was tight and that was why. So this has got to be it.

Again I guess I only have myself to blame as I should have checked before polishing that cutter to make it fit. All the information on the Mast website on the heads showed 8mm and I just never considered anything different. Ironically they have updated the heads since I purchased and they now actually state they run 5/16 valves. Maybe mine were some early ones before they changed the literature?

I measured the Lindy tool down low by the nut and sure enough it measures .3131” where it was not ever spinning in the head. The rest of the shaft was .3115 to .3118”. Even after polishing with steel wool and spinning a ton in the guides it is still bigger than the valves.

Surely this is the problem, I may need all 4 intake guides replaced but the #6 one for sure.