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[Z06] Warranty Replacement Heads at 15k mi. Part II - Bore Gauge Measurements
C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Maybe I am going blind like Michael_D, but I cannot find the .0108" clearance on any on the valves/guides in your table. Where am I missing the boat?
I only have 9000 on my warranty replacement heads. Mine were replaced just before yours and just before the 5 years my GM warranty ran out. That being said, I have a little more cam in mine, running 0.623/0.652 lift. Not sure what the cam lobe design is though. My going in plan was to have the valves wiggle tested at 15000 miles, as you did.
Like you, I have no original valve guide clearances from the install, which was done by Mac Haik Chevy in Houston. My valves, springs, and heads were all separately ordered by Mac Haik, and I have no idea whether they did the head assembly or farmed that out to a machine shop. Although I did the wiggle test myself with help from Jed Blanks last time, I think I will let someone else do the wiggle test next time, someone who can do the R&R on the heads, as it is starting to look like there is a fair chance that it will need it. I expect to ship it out to AHC for the MS90 guides, PSI 1511 springs w/Ti retainers like MTPZ06. I think I will pass on the rocker trunnions. I want to get rid of the PSI 1208X dual springs/retainers that are now on the heads anyway.
I am interested in your report on VZ Autoworks after they complete your work. I have not heard of them before. The other shops I was considering are VettTech (Katy) or 510 Racing (not sure where they are now, but they did a great tune on my Z06). PM me if there is anything you don't want to announce.
Were your original heads replaced under GMPP or under GM warranty? When Mac Haik replaced mine they told me the warranty on the replacement parts was only one year and that is long since gone.
^^^ The .0108 measurement is probably a "raw" wiggle measurement...and I believe the formula is .0108/2 - .0002 = .0054. His chart is a bore gauge (most accurate method) and it looks like he has a guide or two that are very similar to that .0054 number. Just my take on it...
Sorry if it didn't make sense, that picture w/ the 0.0108 reading was from back in 2013 when I measured the first set of heads. See post #8. The picture was just to show the measuring process and the tool used.
This time around none of the guides measured quite that bad, the worst were two intakes with about 0.006. The measurements in the table I posted are all from the 2013 replacement heads after another 15k mi.
I had a very good experience with Victor at VZ. He did the wiggle test, R&R the heads, ordered rebuilt heads from AHP, worked w/ GMPP, etc. VZ is in the same industrial park where 510 used to be.
The whole story in a few words:
Due to excessive valve guide wear, the original heads were replaced at 15k mi. by my Chevrolet dealer using new GM heads and valves and the GM 5yr 100k mi. powertrain warranty covered all the cost. 15k mi later, those heads showed excessive guide wear and were replaced by VZ using AHP rebuilt heads and GMPP covered some of the cost.
Hope that clears it up, sorry about any confusion. PM for more info
^^^ The .0108 measurement is probably a "raw" wiggle measurement...and I believe the formula is .0108/2 - .0002 = .0054. His chart is a bore gauge (most accurate method) and it looks like he has a guide or two that are very similar to that .0054 number. Just my take on it...
I'd heard, measurement/2 - .0005.
Also, don't use a dial indicator, use a "test indicator". With a test indicator you can measure immediately above the valve guide and 100% perpendicular to the valve stem. I intend to buy one this summer when I do my next wiggle test. The test indicator's design gives you a MUCH more accurate measurement than a dial indicator.
Also, don't use a dial indicator, use a "test indicator". With a test indicator you can measure immediately above the valve guide and 100% perpendicular to the valve stem. I intend to buy one this summer when I do my next wiggle test. The test indicator's design gives you a MUCH more accurate measurement than a dial indicator.
Sorry for the thread derailment...
Maybe that was it...didn't go back to check my notes. I'm choosing to have a few coldies, and being lazy today.
(Wiggle/2) - 0.0005 = (Greatest Bore Gauge) actually works out pretty well in practice.
There was lots of discussion a couple of years ago trying to come up with a Wiggle Test = Bore Gauge formula. Just keep in mind that bore gauge measurements can vary greatly depending on how deep in the guide you measure (due to the tapered nature of the wear) and trying to get 0.000x accuracy out of the poor old wiggle test is, um, optimistic at best.
Here's a nice test indicator for not too much $$. Mitutoyo quality and Amazon price.
Same as you...except I was local to AHP for my GMPP claim. I paid for the "upgrades"...MS90 guides, PSI 1511 springs w/Ti retainers, and CHE rocker trunions. I was content with that.
What springs are you getting? Kohle's default spring is typically the BTR duals for his package #4.
Do you think the OE GM Ti intake valves work better with the AHP proprietary powdered metal guides, or the MoldStar90 guides? The reason I ask is because Katech recommends their Ti/Mo intake valves for use with bronze guides only, (inferring that the OE GM Ti valves work better with the material in the OE GM powdered metal guides.)
I have no interest in higher lift camshafts nor do I have any other performance mods planned. I'd like to retain the OE GM stock appearance, sound, and performance. With these goals in mind, I haven't decided between the Ferrea F2042P exhaust valves the OE GM valves. I don't want to add weight to the valvetrain geometry, and the sodium filled exhaust valves are where I want to stay.
I'm otherwise leaning towards rebuilding my heads at AHP with their Package 4 and keeping/replacing my OE GM Springs. Per Katech's testing and research, I think the OE exhaust valves, springs, and rockers are just fine and all the more so in a OE GM stock configuration. Still debating the additional port/polishing. I like the CHE upgraded rockers but not certain I would gain anything since I'm keeping everything else OE GM.
Last edited by BigVette427; 12-18-2016 at 12:59 PM.
Do you think the OE GM Ti intake valves work better with the AHP proprietary powdered metal guides, or the MoldStar90 guides? The reason I ask is because Katech recommends their Ti/Mo intake valves for use with bronze guides only, (inferring that the OE GM Ti valves work better with the material in the OE GM powdered metal guides.)
I have no interest in higher lift camshafts nor do I have any other performance mods planned. I'd like to retain the OE GM stock appearance, sound, and performance. With these goals in mind, I haven't decided between the Ferrea F2042P exhaust valves the OE GM valves. I don't want to add weight to the valvetrain geometry, and the sodium filled exhaust valves are where I want to stay.
I'm otherwise leaning towards rebuilding my heads at AHP with their Package 4 and keeping/replacing my OE GM Springs. Per Katech's testing and research, I think the OE exhaust valves, springs, and rockers are just fine and all the more so in a OE GM stock configuration. Still debating the additional port/polishing. I like the CHE upgraded rockers but not certain I would gain anything since I'm keeping everything else OE GM.
The stock intake valves after we rework them work perfectly with either our hardened PM guides or our MoldStar90 valve guides.
If your looking for ultimate piece of mind you cant go wrong with a set of our heads with MoldStar90 guides. Our PM guides you can go wrong with either but M90 is just a "next level" type alloy.
The stock intake valves after we rework them work perfectly with either our hardened PM guides or our MoldStar90 valve guides.
If your looking for ultimate piece of mind you cant go wrong with a set of our heads with MoldStar90 guides. Our PM guides you can go wrong with either but M90 is just a "next level" type alloy.
That's why I went MS90...wanted to do this once, and not have to think about it again. Sure its an upcharge over PM, but its a drop in the bucket compared to other things for a car of this magnitude...and again, the convenience of getting it done while the car is already torn down is pretty insignificant in the grand scheme of things.
12-07-2016, 02:14 AM
That's why I went MS90...wanted to do this once, and not have to think about it again. Sure its an upcharge over PM, but its a drop in the bucket compared to other things for a car of this magnitude...and again, the convenience of getting it done while the car is already torn down is pretty insignificant in the grand scheme of things.