Gary '09 C6

Well folks, I finally had my LS9 cylinder heads and valve-train fixed last month ! It took me a very long time to act upon this project,
but I feel better now. I’ve just been very busy with work and travel, and was unable to focus on having this matter attended to
during the past couple of years; haven't driven the car much during that time, either.

I bought the car new eight years ago; it currently has 15K+ miles. I don’t do road course work anymore, but I have run the car at the
October Texas Mile from 2012—2016. I have about 75--80 passes total with a p/b of 179.0 mph (all stock). I could not run my car in
October 2017 due to the date-code restriction on the tires, and in October 2018 a C-F friend was very generous in allowing me
three passes in his car over two days. Now that my car is fixed (and the tires replaced). I can bring it back !

Right now I can’t say enough good things about both American Heritage Performance in CA (Harbor City/L.A.)
and 21st Century Muscle Cars in TX (Addison/Dallas).

I spoke at length with Kohle at AHP last year about recommending a work plan to address this issue for my OEM stock C6 ZR1.
He recommended (in writing) new treated GM stock valves, Moldstar 90 valve guides, PSI 1511 springs w/titanium retainers,
and some mild porting/milling still allowing me to keep the stock cam and tune. (Kohle says this specific porting/milling also adds
about 30 to 40 hp at the crankshaft).

I accepted these recommendations ! During the build process, both Kohle & Jake were very accessible and kept me informed.
They even sent me their internal build sheets and pictures of the newly-machined heads to keep with my documentation.
My original LS9 cylinder heads were removed and shipped still assembled to AHP for core exchange. I had AHP measure
the valve-guide clearances to document the “out-of-specification” condition of the guides.

Matt G. (Shop Director) and James V. (Technician) at 21st Century Muscle cars were equally helpful. Matt provided a work plan
for the labor for this project, along with other deferred maintenance that was needed: R & R the cylinder heads; flush, re-fill & bleed
engine and S-C coolant; oil/filter change (M1 0W-40 w/UPF-48R filter); clutch system flush, re-fill & bleed; brake system flush,
re-fill & bleed (Motul 600 used for the latter two items). In addition, Matt arranged for new tires to be properly installed
(MPSS ZPs in OEM stock sizes) and for a new four-wheel alignment to be done (to Pfadt Performance Street specs).
I also had front & rear tow hooks installed !

I retrieved the car recently and drove it back home…it was just glorious knowing all the work was complete !
The ambient temperature was in the mid-50*s F that day and the new tires were fine. The car ran great !
Keep in mind, the car always ran great before this engine project…but I knew it needed to be fixed.

Years of reports and vigorous debate on the C-F regarding both LS7 and LS9 valve-train issues just could not be ignored.
A collective thanks to everyone who shared knowledge and participated in those on-going discussions.

My thread compiling a list of LS9 valve-train matters reported on the C-F continues to document the latter:

https://www.corvetteforum.com/forums...on-the-cf.html


The message regarding possible accelerated valve-guide wear for these engines still needs to get out. I have concluded some time ago
that all LS7 and LS9 engines are potentially affected, and need to be properly checked for this issue.

I hope my own experience and information is helpful to others.

Gary
















posted with permission of AHP




posted with permission of AHP







AHP measurements of original LS9 heads...

blackvetterzo6

What may i ask did this cost. Looks sweet

Gary '09 C6

thanks...PM sent.

MTPZ06

Congrats Gary! Glad you took care of this. Seeing the intakes out of spec doesn't surprise me...GM clearly learned that skipping out on the micro-polishing step for the C6 Ti valved motors was a mistake. A mistake they aren't willing to admit; but nonetheless, they corrected that mistake going forward in the C7's. Go figure...

EDIT: Also, thanks for taking the step to go bore mic on the measurements...eliminates all the "wiggle" blah blah noise that can typically accompany such a thread.

Gary '09 C6

thanks Mike !

American Heritage

Hey Gary, Great Thread!
PIcs and Hard Data what else could anyone ask for!!!

Thank you for the nice words about Jake and Myself!
We pride ourselves on building some of the best LS heads in the industry backed by the best customer service you can find anywhere.

Gary thank you again for you business and this AWESOME thread with all the data and pics!
If you ever need anything dont hesitate to let us know.

https://www.americanheritageperformance.com/

Boba Fett

detailed and descriptive as usual, nice Gary