Hi Guys,
I´m hoping to get some advice from pro´s.
Short backstory, I´m in Germany and bought a wrecked z06 that was rear ended and rebuilt that, haven´t really put a lot of mileage on it yet.

A friend in his z06 dropped a valve a few days ago, so i got super paranoid about mine (97k miles) I planned to do it in winter, but after seeing his carnage i immediately pulled my engine.
Especially since mine blew some blue smoke on decel after a 4700 rpm decibel test. Also it made some, what i can only describe as light misfires during idle which caused the idle to drop maybe 30-40 rpm every so often.

Engine is completely stock from what i can tell.

My plan was to just replace the guides, cut the seats and put it back together but then i saw some scoring in the cylinders, presumably from some of the carbon coke that fell off the valves.
I can definitely feel it with my finger when going over it but i can´t catch a groove with my fingernail.
Car has been running stong until i pulled the engine.

Hence why I´m seeking help. I wasn´t planning to fork out the cash for a full rebuild with new pistons etc.
Can the Pro´s look at my pics and see if i can just run through the bores with a 3 stone hone and maybe deglaze with a flexhone and put the pistons back in with maybe new rings?

Also another question about the valve guides. It seems only my intake valves are badly worn, the exhausts arent nearly as bad. I attached a short video where i go through them. I guess my issue is less with non-concentricity as much as it is with the rough CrN coating of the Ti intake valves. I´ve been doing lots of research but there´s just so much. I´ve been contemplating getting the AHP Moldstar90 guides which are longer. But i heard the CrN coating doesn´t work very well with the Bronze guides. Should i put Bronze on the exhausts and AHP PM guides in the Intake? Or just put the cheaper CHE guides in and check every 5k miles?
Since my exhaust guides aren´t so badly out of spec, can i reuse them without fearing that they suffered damage already and may drop even with replaced guides?

Attached are the pics.
Here is the Video

Thank you very much
Max

 

Those intake stems look bad... Good thing you decided to pull them off.

Moldstar90 and Ti Moly work amazing together. In fact MS90 guides and Ti moly intake valves is about the best combo you can go with. We have seen zero wear from the Moldstar90 and Ti Moly Combo even on high lift race engines.

We also ship to Germany (we have a few sets of our heads on c6z06s over there).

Shoot me an email if you have any questions
HP@americanheritageperformance.com


https://americanheritageperformance.com/

 

Hi,
Thank you for your answer
Do you mean the exhaust valve stems? the intake valve stems look like new and measure like new
Ive heard that the Ti Moly(bdenum) valves work well with bronze, however the ls7 intake valves are CrN coated, are they not? I´ve read that they wear through the bronze very fast.
Thanks
Max

 

No I meant the Ti intake stems look bad. The exhaust stems look obviously terrible.
Correct the factory LS7 ti intake valves are CRN coated and that coating on some of the valve in your pictures appears to be damaged. In short any small defect/damage in the factory ti intake valves CRN coating on the stem renders the valves junk. In your pictures some look like they are polished tword the bottom of the valves. The polish look on a crn coated stem is bad and is where the coating has essentially been worn/polished away.
Take some more up close pics of the intake stems and post them up and I will try to show you what im seeing.
Yes Ti Moly intakes is the way to go. Ti Moly works great with Moldstar90, Bronze and even PM guides.

https://americanheritageperformance.com/

 

Here´s some more stem pictures. i tried my best with the photos and light, it´s hard due to the round, shiny surface. the close ups are from the two worst valves, the rest looks pretty good.
If i replace those two valves, would they live with the moldstar90 guides or would they see-saw through there too? I don´t know if i want to swallow the $1500 Moly intake valve pill, or rather, bill.
What about the exhaust valves? Since none are really worn, they are all around the service spec, can i reuse them or should i go for solid stainless exhaust valves? Which springs do i need to run then for the heavier valves?
Can you also comment on the scuff marks on the cylinder bore? Would i be ok with a deglaze? I wasn´t trying to spend crazy money on this rebuild

 

Anyone?