MTPZ06

Anytime! Hopefully with the Lingenfelter build in your car, you'll check out to be alright. I'd say the odds are in your favor certainly over that of a stock GM engine. By all means though, better to be safe than sorry and have a quick look at the valve guides to see what going on.

SkymonkeyONE

46,000 hard-driven miles

Precision Race Components 285cc LS7 CNC heads by Texas Speed
Texas Speed LS7 cam
ARE dry sump system/reservoir
FAST LSXr 102 mm intake, throttle body
BillyBoat long-tubes, X-pipe, Bullet exhaust (incredibly loud)

Mobil 1 oil (9 quarts of it) at 3000 mile intervals

Hard street driving and power touring. I'm very hard on back tires.

InfernoZ

Mileage - 9500

Material - GM Factory Certified Heads.

Parts

Car used for.... Pleasure, Weekend Joy Riding.

Cam, Stock.

Follow up disassemble and data. Abel Chevrolet.

Oil change intervals... 3K

Type of oil, Mobile 1 5W30 Synthetic.

All seems to be ok, I have only driven the car a few hundred miles.

important

In which year did GM finally resolve this issue?

encasedmetal

Mileage-27345

Material-Advanced Induction 280cc CNC ported heads with CHE bronze guides

Parts-PRC 0.660 dual springs w/titanium retainers, Vararam CAI, Kooks 1 7/8 LT, Kooks O/R xpipe

Car used for....weekend beatings

Cam-244/252 0.640/0.650 lift

Follow up disassembly and data. n/a

Oil change intervals...once a year or every 3k miles

Type of oil - mobil 1 5w30

MTPZ06

Never...it hasn't happened yet, nor will it ever. GM simply has no plans to look into this...they've moved on to brand new shortcomings to ignore in the C7Z.

Too-Fast

Excellent response! This made me laugh! Great

MTPZ06

LOL...its sad, but true. GM knows people are experiencing heat soak and overheating issues with the C7Z when pushed at the track in "warm" weather. How do they handle this? By ignoring it. They know that consumers will either accept it for what it is, or turn to aftermarket accessories that will in turn void your warranty. Win-win for GM.

important

So regardless of which year Z we buy or how low mileage it has, the possibility exists that the valves may be too small and can fall into the cylinder at any time?

MTPZ06

Yes to the first part of your question...all years are affected. So this means it's an LS7 issue, not a C6Z issue...427 vert, Camaro z/28, etc.

As for the second part of your question...it's not a valve size issue; in very simplistic terms, it's a guide machining and stem to seat concentricity issue that causes excellerated guide wear.

important

Mmm hmm, indubitably.

GLmajer

American Heritage Performance, 2008 Z06, 23900 miles. Installed AHP Stage 4 performance kit. WOW!

LeManscoupe05

2009 JSB Z06 with 56,000 miles

Abel Chevrolet in Rio Vista

Today

agleason

2009 16000 miles. AHP head rework package. No problems at all.

American Heritage shipped reworked heads to me and I had a local shop (21st century muscle cars who were also great) install them. I worked with Khole at AHP who is knowledgable, professional, and made me feel comfortable with the whole process. I read fantastic reviews about AHP prior to fixing the heads and was happy to find the reviews were accurate.

I would highly recommend both AHP and 21st century muscle cars.

Adam

AzDave47

My 09 Z has 46K miles. I worked with Cordes Performance Racing on my HCI install. They sent out a set of LS7 heads with 20K mile to WCCH for Stage II with Che bronze guides, Katech TiMo intake valves and new OEM exhaust valves, Ti retainers and PSI 1511 springs.

The heads from my car are being redone at WCCH and will go on another CPR LS7 build. I'll report on guide clearance specs from my 46K heads in the next week or two.

Here is the thread on my guide spec, all exhaust valve guides and 6 of the intakes were out of spec.

https://www.corvetteforum.com/forums...d-exhaust.html

bd4airman11

Did my own work about a year and a half ago....I had a small shop in Moses Lake, Washington do all the machine work....Precision Engine Machine...Joe did a great job.
I bought all the parts I wanted and they put them in the heads.......
And YES, at 30,000 easy miles the stock set up was so bad I still cringe at what I was driving around with...............
YT rockers
Ferrea SS Ext.
BTR Ti spring kit
BTR stage 3 cam
Texas speed hardened pushrods
Tommy Wong tune
Mobil 1
Tommy put 526hp to the ground and is the best to work with ever...."Thanks Tommy"
Very happy with my build...After 1 year I checked everything and it is running clean and no problems.....

American Heritage

Thanks for the nice words/ review Adam.

http://www.americanheritageperformance.com/

_BlueZ06_

I forgot to post when I redid my heads.

Reher Morrison

Year: 2008

Mileage: 20,900

Material/Parts: CHE valve guides, SS exhaust valves, stock intake valves, Valve job.

Car used for: Street and track usage

Oil change intervals: 2-3k miles or two track weekends

Type of oil: Joe Gibbs 5w-30

User Omega

Was done 2012

WCCH CNC Level 2

Year: 2008

Mileage: ~6000

Oil change intervals: 2 dealer oil changes

Oil: Mobil 1 5w-30

Use: Street only

REDZED2

2008 VR 3LZ Z06 12,600 miles

Advanced Induction 260cc ex. port 100% cnc ported.CHE Precision bronze guides. Hollow Ferrea ex. ss valves. Milled .025.

Stock cam.

96 octane.

Comp. Magnum 7.750 PR's. Stock rockers.

Mobil 1 0W 40 European Formula from now on. 1 oil change every spring.. less than 2K miles a year from May to October.