99Hawk262

AHP on both of my Z's. On the 2009 I sold it was the basic package with MS90 guides. On my current car, I stuck with the PM guides at the advice of Kohle and upgraded only the springs to PSI 1511's. My only regret while swapping is that I didn't check the lifters. Oh well, gives me motivation to upgrade the cam sooner than later. No mods currently outside of Borla Atak. I have ARH 2" LTs and catted X waiting to go on this spring (great black Friday sale on them, and getting the bolt ons out of the way so it's ready when I decide to go after the internals).

moose.b3

08Z with some track use. At 38,000 miles GMPP paid for new GM stock head replacement because of valve guide wear. At 60,000 miles and only 2 months of GMPP left, I had the wiggle test done to see if there was any indication of worn guides. There was and this time GMPP paid to have AHP fix the heads. I paid to have some upgrades and went with stage 4 with street porting, PSI 1511 springs, new lifters and MS90 guides.

Z064me2enjoy

I went with SPS in Kent, Washington. They put together a package for me that it would be hard to refuse and they have a shop (TMS Performance) they work with there that will do the labor work for $880.00 (8 hrs @ $110.00) They service your heads, valve job, use powdered guides, polish intake valves, use solid stems, new OEM head-bolts TTY, upgrade to Comp 7228-16 Conical .625 Valve Springs, mill the heads, head gasket, new oil and filter and antifreeze, filter flush, spark plugs for $1,725.00 plus $880.00 labor = $2,605.00. 2-day turn around. Talked about adding a BTR Cam with springs and pushrods with labor would be an additional $2,239.00 includes a tune. They offer pretty much anything you want but we felt comfortable that the basic head package would meet my needs. Very pleased with the finished product. They found all my valves guides were within specs at 48K miles but I decided to go ahead and have the work done. I spoke with a few others who have had there heads done with SPS who said not only did they do quality work using quality parts but just as important they stand behind there work! From being in the automotive repair business a few years my self in the past, thats important to me! Customer service........I try to learn from others mistakes. Happy motoring.

GTAZ06

I’ve got a set of AHP heads on the way. MS90 otherwise stock. However, I too would like to bring up the point that our guide wear issue could very well stem from lack of oil intrusion into the guide past the valve seal. Obviously the machining issue is real, but lack of lubricant makes matters worse. Your typical Engine with worn out guides will burn oil, puff smoke at startup, and have oil in the intake runners. We don’t typically suffer from that. Why? I believe the guides, are for the most part, dry. My reasoning for this is the cold oil temps that most all of us low mileage cars suffer from every time out. The “cold” oil can’t penetrate the seal properly. When my heads go on, I’m removing my oil cooler in hopes that if my theory is real then the problem will improve. Not trying to start anything. Just wanted to throw my ideas out there seeing that it was brought up a few posts up.

SSMOKE

In 2013 I was anxiously waiting the results of KATECH'S spintron testing. I was so paranoid that my 2007 Z with 10,000 miles was going to drop an exhaust valve, I ordered WCCH Stage 2 heads with bronze guides and SS exhaust valves before KATECH'S results were posted. (IIRC the spintron test results came out the day I received my heads from WCCH.) Those results did not inspire confidence in the decision that I made to go with the WCCH Stage 2 head package. (A TORQUER 110 was installed with the heads.)

Six years later (2019) my car has 24,300 miles. (14,300 with WCCH heads and TORQUER 110) Lately, I have been going through so much oil that I can not keep it on the dipstick. (FYI It NEVER smokes.) Last week I received my third oil analysis from BlackStone and copper went from 5 to 25 to 266. I am not a head builder or mechanic, but my guess is that the guides are worn out and again, I am paranoid to drive.

Because I can not sell the car believing it has worn guides, I am working with Kohle at AHP and it is likely that I will get their Package 4 heads with M90 guides. Needless to type, this is kind of an expensive nightmare.

Currently - WCCH Stage 2 with bronze guides, SS exhaust valves, T. polished OEM intake valves, BT dual springs and Staub trunnion upgrade. TORQUER 110 (.616 / .648)

On deck - AHP Package 4 with M90 guides, Ferrea hollow F2042p SS exhaust valves, T. polished OEM intake valves, PS1511 springs (I think.) and Straub trunnion upgrade. TORQUER 110 (.616 / .648)

Formula8

I have posted my thoughts on this three times and it never seems to get any discussion although it makes the most sense and is entirely consistent with the experience of people who have had their heads "fixed" again by multiple shops. I guess debating over which shop does your heads is sexier.

Formula8

I spoke with SPS extensively. They were extremely responsive and you can't beat the value anywhere. They get a lot of great reviews on Facebook. I ultimately went a different direction though and it may just be comfort level, no slam intended against either SPS or your choice to use them. Here were my issues:

1) When asked about what valve run out tolerance they can maintain, they state they have up to .001 per inch of of valve diameter. Otherwise around .0022. My understanding is that is rebuilder tolerance and not what I am expecting from a "competition valve job" as they advertise. In my opinion, that is near the service limit and for an application known to have valve guide issues to begin with and using the equipment they have, that is too much run out for my comfort level.
2) They finish the intake valves by hand with Scotchbrite. While you may get a satisfactory finish with this, I have no idea how you maintain consistency. Again, I am not comfortable with the process.
3) The comp spring they recommended for my application was spec'd for a 1.800" installed height. I asked them if they were using LS3 retainers to avoid excess shimming to work with the LS7 installed height of 1.959. They replied no, as the LS7 installed height is 1.800 their spring is a drop in and the LS7 spring is just spec'd out at 1.959. When I pulled my heads, my IH measured 1.955. Doing the math on the springs, if just dropped in, the comp spring would deliver far less pressure than the stock spring.

I really wanted to send my heads to SPS but considering I paid a premium for the car because the heads were previously fixed and the repair is not being covered by my extended warranty, it really didn't make sense to me to take chances just to save $500 at that point.

El Paso Vette

Heads completed by Cordes Performance Racing in Phoenix at 60,000 miles. Got CAI, Mighty Mouse catch can, American Racing Headers and exhaust while I was at it. The performance is noticeably quicker and more responsive.

Katech_Zach

When I see heads that have been repaired but have worn out again it's always with OEM (sometimes polished) intake valves. We tried tumble polishing the valves and did not achieve the surface finish we desired. The chrome nitride coating is too harsh on the bronze and will wear it out, creating a slurry of oil, guide material, and chrome nitride which just accelerates wear. When we use bronze guides with titanium/molybdenum-coated valves they don't have issues again.

RamAir972003

I had a who did you heads sticky moderators did not put it up can you please put sticky back up it's very informative....thanks.