AW794

iTrader: (7)

Have any vendors experienced a "bad" batch of stock ls7 heads? Over on cf, there's a bunch of guys that are dropping exhaust valves. Kinda making me a little concerned as my car has the (what has been determined "normal") ticking between 1500-2500 rpm. I'm suspecting that there is something amiss with the rocker geometry causing excessive valve guide wear but don't have any real evidence.

I was hoping some venders could shed some light on this.

AWDTBSS

Interested to hear what LS1tech vendors have to say

AW794

iTrader: (7)

That's what I was hoping for.

whatcop?

I can tell you that my 07 dropped a valve. I can also tell you I haven't seen outside of 06-08 cars do it. Also a thread popped up recently on cf claiming it was a manufacturer problem in the geometry of the valve tunnel in the heads themselves.

AWDTBSS

There has been a 2010 that has, stock iirc

whatcop?

Wasn't that one due to a spring failure. I was referring to valve heads breaking off.

AWDTBSS

Can't remember, so much of this posted on cf I lose track lol

ramairws6

iTrader: (33)

My guides were all wore and out of spec on the exhaust side. Richard at WCCH redid my heads and is pretty confident it's a heat issue on the exhaust valve and it's cooking the oil and gauling the valve and thus wearing out the guide. The stock valves are also 2 pieced and sonic welded at the head of the valve. There also has been some shown to be very inconsistant in the stem thickness after cutting them open. Get new bronze guides put in and get those sodium filled stockers out and all will be fine

merim123

iTrader: (11)

if you read through all the CF threads, this is happening but it's not a catastrophic failure of ls7 engines. probably 1% of all engines having issues and most of the issues are coming up on cammed cars.

ramairws6

iTrader: (33)

I believe this to be untrue as most of the stock Zo6's haven't been apart so the only way we find out if the guides are out of spec is if they pop their motor. My heads were stockers when i bought them and all exhaust guides were out of spec....

whatcop?

I agree with your cause more than the whole geometry issue. I think GM changed the oil pump to the higher flow rate ZR1 pump in 09 but never revealed it. Jason from Katech at one point even stated that the sprocket on the Z06 from 09 on was that of the ZR1. Doesn't make much sense to only change the sprocket and re-engineer the oil pump to fit the new sprocket.

Higher lift cams would exacerbate the problem above. More lift means more travel which means more heat.

Frans96SS

iTrader: (15)

They all do it. Its not a bad batch... LS7 exh valves are hollow and break... Replace them with stainless valves.

whatcop?

Hey Fran do you see the same amount of failures or valve play in the 09-12s as in the 06-08?

Frans96SS

iTrader: (15)

I havent seen a difference from the years.

AWDTBSS

Fran which would you do:
1. Have WCCH do their Stage 2 package heads with the SS valves, comp cam 3/8 7.800 push rods, trunion upgrade, and manley springs with reused stock intake valves
Or
2. Buy Texas Speed PRC 285cc heads with titanium intake/SS exhaust valves

If there's any changes to any of those setups feel free to chime in

AW794

iTrader: (7)

Thanks for taking the time to respond. In your opinion, what is causing the excessive valve guide wear?

AWD if it were me, and it might be soon. I think aftermarket casting might be the way to go. It would completely rule out any geometry issues stock LS7 heads might have. Not sure if there is even a problem, but something is definitely wearing out the valve guides

blackonblacksls

iTrader: (1)

Rich at wcch said its the valves lack of ability to pull heat out of the stem that cooks oil and kills guides. This leads to the failure.

ramairws6

iTrader: (33)

??Hahahaha..... isn't that what i just posted above??

Katech_Jason

iTrader: (19)

There was some speculation that the LS7 got the LS9 pump after 2009, but it wasn't the case. The LS7 still gets the same pump that it did in 2006. The crank sprocket changed in 2009 to accommodate the thicker pressure section of the LS9 pump and rather than continuing to make two sprockets they just made the one sprocket go on both engines since it fits on both. A 2009 crank sprocket will fit with a LS7 oil pump, but not the other way around.


To answer the OP, there is nothing wrong with the LS7 exhaust valves. There is a frenzy of people on the Corvette Forum who refuse to accept that conclusion, but we are continuing to use them in racing engines that we have to stand behind and we do not see a problem. We are seeing excessive guide wear (intake and exhaust) on LS7 and LS9 (especially with higher lift camshafts) which we are continuing to gather data on, but we do have a fix that we are doing for any track-going car which is bronze guides and our titanium/molybdenum intake valves.

427LS7HCI

I heard that bronze guides and SS valves were only a bandaid to the issue.