[MeanGreen1LE]

“Fly cut they said it will be fun they said”. During the crazy supply issue times I talked myself into fly cutting instead of waiting on the .040” gaskets that were months out. Not my proudest moment but maybe one of the most frustrating ones was botching that up in a big way. I was having issues with the lock collar slipping as well as the tool inconsistently cutting and I went too deep. That necessitated buying drop ins in which Ironically I waited even longer than I would have for the gaskets doh!

But now I’m afraid this fiasco is still haunting me as I think maybe I reamed out the guides past spec by going at it so long with the drill/lindy tool.

I’m still having oil issues; namely oil sitting on back of intake valves with # 6 being the worst.
I only used one head to fly cut all 8 intake valves and since one head seems to be the problem surely this is the issue?

Anyone seen this happen or maybe have suggestions for a mail to cylinder head shop that could replace the guides.

I’ve asked this elsewhere and it seems most people think it’s not likely I bore the guides out of spec. But I will say the fly cut tool felt kinda snug compared to valve at first and I polished the tool with super fine steel wool to make it fit better. Just curious to see if anyone over here had any ideas or suggestions about where the oil might be coming from. Rocker bolts do not go through intake tract.

[Katech_Mike]

To R&R the valve guides would include installing bronze guides.

The cost would be around $900 + shipping.

The only OEM replacement guides offered are Chinese and have a tolerance that is non existent. We refuse to use them.

[MeanGreen1LE]

Originally Posted by Katech_Mike

To R&R the valve guides would include installing bronze guides.

The cost would be around $900 + shipping.

The only OEM replacement guides offered are Chinese and have a tolerance that is non existent. We refuse to use them.

I get that, it would kinda defeat the purpose to use guides that might be just as bad. These are Mast heads btw. Don’t know if that makes a difference or not.

[MeanGreen1LE]

I’m unsure of the validity of this test I created but it makes sense in my mind and points to my guides being out of spec. Laying awake last night I got to thinking about how to simulate oil leaking past the guides and seals with the car mostly put together. Yesterday I blocked the oil return in my heads and tried just pouring some oil over the valve spring assembly but never saw any leakage. Felt that was inconclusive and was thinking about how I’ve read over and over that bad seals and guides will often leak after getting on car semi aggressively and then letting throttle slam shut creating a vacuum that will pull oil through seals. Starting doing research on what vacuum cleaners would pull and learned that the intake manifold vacuum is significantly higher when throttle is shut like at idle. (Average household vacuums are in the 20kpa range my test is with a well used craftsman shop vac but would still be significantly below vacuum in manifold.)

Test procedure:
Cut a hole in a small plastic cup to place over spring to simulate oil in head.

Vacuum hose was just slightly too small to seal around intake port so I used electrical tape to seal a little better.

Turned vacuum on and began suction

Poured oil in cup till it was at the top.

I forgot to start timer but wife said vacuum was running about 3 minutes before oil ran out of cup. (It was not a perfect seal at bottom)

See pics.

[Katech_Mike]

Originally Posted by MeanGreen1LE

I get that, it would kinda defeat the purpose to use guides that might be just as bad. These are Mast heads btw. Don’t know if that makes a difference or not.

Not much difference as far as cost goes. Would just need to order the correct OD and length guides for those specific heads(if they do not use standard size).

I would take the heads to a repeatable engine shop. Have them disassembled and measure the guides properly with a dial bore gauge.

[MeanGreen1LE]

Originally Posted by Katech_Mike

Not much difference as far as cost goes. Would just need to order the correct OD and length guides for those specific heads(if they do not use standard size).

I would take the heads to a repeatable engine shop. Have them disassembled and measure the guides properly with a dial bore gauge.

Yeah that’s probably what I’m going to do I just wanted to do what I could to make an educated guess on the problem before I get to deep on the car. If I have bottom end issues I think I’m going to take it somewhere. I’m not sure I have it in me to pull the engine yet again on this one. Ready to move on to something else. Going to do a leak down test this weekend and if it shows good numbers or close to others I’m pulling head.

[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.

[6spdhyperblue]

Thanks for sharing

[MeanGreen1LE]

Just got word from the head shop that all the guides checked out fine. So I’m back to square one. I guess the difference in the valves was not enough to ream the guides out of spec enough to matter. Now I just don’t have any clue where the oil is coming from. Ugh!

[Katech_Mike]

Are you certain the intake rocker arm bolts aren't coming through the port? I have seen core shift on heads that allow the intake rocker bolt to poke through only certain runners and not others.

Also check the roof of ports for hairline cranks from spring pocket machining.