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Drop vavles, cam

17K views 37 replies 21 participants last post by  bumblebeeZ06 
#1 ·
Dang it, I was shopping today for cam, long tube headers, I was told that heads need to be redone for valve drop issues, before I get started I am not going say were the shops are, they are very well established shops that back there stuff and have a very great REP.
As a bonus I was shown the heads and the problem, trust me when I say this there is a problem. My question to all you peeps, has anyone else been told they need to address this issue first.
From what I have been told by both shops its mainly on the LS7.
 
#8 ·
Yes if you are going to race your 06-07 Z06 have the valves replaced.

Mine dropped a valve at 30k miles luckily it was still under warranty. Took the whole engine and cats. with it. The warranted bill at the Chevy dealer was over $17k...:thud:
 
#9 · (Edited)
Its the valve guide I seen first hand one that was getting ready to go and one that has. As far the year and Gm they filed bankruptcy. So no deal for replacement for me under warranty.
This a very serious problem modded or not.
 
#27 ·
Yup. My showroom stock 2006 had defective valve guides. Luckily I detected it at 38,000 miles, before anything catastrophic happened. Last month I replaced my cylinder heads with stock heads that had been overhauled by WCCH to replace exhaust valves with stainless steel, and replace stock sintered metal guides with bronze. Cost me 4 grand. but at least I avoided a valve drop, which most likely would have resulted in a blown engine. Some say 50% of all LS7 engines have defective guides. GM's official position is that the numbers are very small, and limited to those produced prior to a certain date. The truth is perhaps somewhere in the middle of these two extremes.

Here's an easy test that every owner of an LS7 should perform: remove your spark plugs, and inspect the threads (yes, threads) for oil. If your plugs have oily threads, there is a strong possibility that your valve seals, and your valve guides, are defective.
 
#11 ·
One easy check that you should do is to pull your spark plugs...see if there is oil on the threads (the threads should be dry). Oil on the threads indicates valve seals and guides are probably shot, and need R/R before a catastophy happens. Dry threads is certainly no guarantee that all is well, but wet threads indicate upcoming trouble. Some have said that if you have oily threads on your spark plugs, that you should PARK YOUR CAR, and not drive it until the heads are fixed.

Once valve guides are shot, the valves can wobble, and eventually break, with the valve head dropping down into the engine, only to be hit by the piston, which breaks a rod and puts a hole in the block. Soon after that, the really bad stuff happens.

Good luck.
 

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#13 ·
What Raid and Ivan said. Remember, the LS7 rocker ratio is 1.9:1, so the ramp is more severe. Couple that with a 7k red line and a bigger cam, the valve springs are going to take a beating. There were a lot of documented spring failures in the earlier LS7's...then sump issues...supposedly all fixed in 2009. If you are going to road race the car, I would suggest looking into improving the sump system.
 
#16 ·
Ther rocker ratio is 1.8 on LS7, there are documented dropped valves from 2006-up through 2011. Due in most part to bad or worn valve guides, or bad valve train geometry by some...Bad needle bearing end caps in LS7 rockers from jan 2007-late July 2007, bad batch...caused needle bearings to end up in oil pan.
 
#14 ·
I have posted this before but it deserves repeating...

It is critical with an LS7 to warm up the motor before beating it. The tollerances on this motor are very close and designed to only be correct when the engine is at opperating temps. Metal expands when it heats up and aluminum moves much more than cast iron.

I never rev higher than 3000 RPM until the engine oil reaches 100 degrees. Do not go by water temp as that is controlled by the thermostat to get hotter sooner.(the hotter water helps warm up the metal) The metal in the engine needs to soak the heat to expand into it's design specs. The metal temp is better represented by oil temp than water temp, and there is no metal temp guage. :thumbsup:
 
#20 ·
Last month a valve dropped from my buddy's 2006 Z06, A bone stock street car, with ony 37K miles. We removed the heads and found the cylinder sleeve cracked, most probaly another LS7 engine written off.
My Z06 was a only few cars later on the production line, with 35K miles also completly stock, both of our cars share the same defects which came along, cracked starter button, doorpads, clutch fluid, battery etc. To avoid valve drop problem with my Vette, I decided to replace the exhaust valves for the new Katech Ti/Mo exhaust valves. With the Molybdene steel stem they run excellent with bronze guides. I want to keep my original Ti intake valves but want to replace the guides. These all Ti guides doesn't run well with bronze guides, so I want to have the original Sintered steel guides. But they are not easy available, anyone has suggestions ?

Thanks in advance,
Regards,

Mang
 
#21 ·
Last month a valve dropped from my buddy's Z06, A bone stock street car, with ony 37K miles. We removed the heads and found the cylinder sleeve cracked, most probaly another LS7 engine written off.
My Z06 is only a few VIN later produced, with 35K miles also completly stock, we share all the defects which came along with our Z06, cracked starter button, doorpads, clutch fluid, battery etc. To avoid valve drop problem with my Vette, I decided to replace the exhaust valves for the new Katech Ti/Mo exhaust valves. With the Molybdene steel stem they run excellent with bronze guides. I want to keep my original Ti intake valves but want to replace the guides. These all Ti guides doesn't run well with bronze guides, so I want to have the original Sintered steel guides. But they are not easy

available, anyone has suggestions ?

Thanks in advance,
Regards,

Mang



Check with Lingenfelter, I believe they have access to the original guides...See if you can speak with Graham Behan, cheif engineer at LPE...Also, if the Ti Valves are coated properly with the Molyb, then bronze guides will be fine...See bold on your post ...
 
#22 ·
Shop vrs HOME SHOP

I do not drive my vette much right now but looking at the shop doing the work vrs me right now the shop has me beat 2 yr 24 warranty, for 7500, cam head work port polish headers and a tune, doing the work I would save a little money but no warranty:thumbsup:. Very hard not to let them do the work.
 
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#23 ·
It really does not matter what year, from what I have been told and have seen at the shops, it would be in my best interested to do the job on the heads. The great upside is better flow and power. For a little more cash its worth it:thumbsup:
 
#25 ·
So to sleep better at night, I need Valve / Guide / Spring replaced on heads?
(I'm not looking for any HP increase from head work)

If I were to get some reputable shop to do this work, how much should I expect to pay for the work? (head refresh and install)
 
#26 ·
You need new valves. I am getting mine done this Friday. Going with Stainless Steele ones. Since my heads are going to be done and engine opened up, I am also throwing a mild cam and other things.

I have researched this issue for two years now and was initially very weary about modding my Z. Since my warranty just ran out, I am doing something to get a peace of mind.
 
#29 ·
I looked into this and its not my first time doing heads.
Goodson is the one place to look for the kits, but when it comes right down to it, if you mess up,,,,, well you know. If you let a CNC machine shop mess up its there cost. jm2cents
 
#31 ·
Like the earlier poster, I've been following the "dropped valve" story for around 2 years now. If you go to "the other forum" and look around the Z06 section, you have to dig through cat fights and drama, but will eventually find the info.

An overview? GM released an official statement saying that a "machining error" had occured at the head supplier. Officially, they stated that this affected "a small number of cars", and was "contained as of February 2011 with all heads inspected after that date". One milling machine had been setup wrong at the head supplier. Now, exhaust valves have been dropping on LS7s starting with the 2006 model year. Considering how few LS7s are sold each year, how many head milling machines do you suspect the supplier had? Well...."the other forum" asked its members to pull their valve covers and showed them how to measure the amount of wiggle (or play) their exhaust valves showed on a gauge. 40 members have done it so far, and JUST OVER HALF ARE OVER THE SERVICE LIMIT FOR EXHAUST GUIDE WEAR. The numbers, photos, and owner reports are available. This is why quite a few people think that there might be two machines producing heads at the supplier, and if one of them has been setup wrong from 2005 to 2011, then that would mean that half of the LS7 heads in the field are machined wrong. This may be correct, and it may not even be close. Do not know. But, that is where that came from. They continue to have members check and report, so it will be interesting to see where the numbers go.

That forum has -tons- of blown LS7s from cars that were never tracked and were bone stock. One of the cars that received a replacement LS7 under warranty for a dropped exhaust valve had severe misfire at 400 miles. Turned out to be caused by excessive exhaust valve guide wear! ALREADY! AT 400 MILES! Valve was closing crooked! Here is the kicker, This replacement warranty engine from GM had a build date of September 2012. LONG after GM claimed the problem was fixed.

There will always be those who do NOT have a problem. One of my friends with a 2006 Z06 has 92,000 miles on his and NEVER a problem. I assume he got heads from the good machine! LOL! But, guys.....at this time we just do not know the truth. Is it really 50% of heads? I don't know. BUT, I personally have zero doubt that this IS a very real problem. Considering how few Z06 are sold each year, and how few of those buyers post on forums, an alarming percentage of those who DO are showing up with blown motors. I *will not* overhype or try to scare people, but I do feel this is serious enough that everyone should be aware of it. Everyone should NOT ignore it or claim it does not exist. Everyone should do some reading to learn what symptoms to look for (louder than normal valvetrain noise and oil on plug are bad signs), but be aware that some cars have dropped a valve with NO warning signs. If you track your car or go with an aftermarket cam then you are really playing with fire if you do not have your heads done. Bone stock cars are at risk as well. The bad part is, we just do not know how high that risk is.

WCCH is the place that most people and shops alike send their heads to for valve guide and valve replacement. Katech sends their heads there. I do NOT yet own a Z06, but once my Xterra is paid off this fall I plan to buy one to go with my Viper. Yes, even knowing about this issue. Because MY plan is to either buy one that has already had the heads done, OR I will simply budget that in as part of the buying process. Once the heads are done, I will KNOW that I do not have to even wonder if the car is ok. Small price to pay to enjoy such an incredible machine. For those of you who will choose to not worry about it and not do your heads, I am completely cool with that too! Enjoy your cars. But I did at least want to let everyone know that this issue was out there.
 
#38 ·
Yes, I have seen all of the posts on the other forum. As you stated there are lots of cat fights and drama. But once you read through all of it you get a sense of this problem. But its unclear how big or small it really is. I am not going to abandon GM because what has happened, in fact I purchased a 2013 Zl1 last October. As an engineer I understand how problems like this can happen when manufacturing work is subcontracted out to other companies. I have dealt with it many times in my profession.

Your plan to budget this as part of the acquisition process on C6Z is a good idea. But what is good to hear, are the C6Z owners with high mileage on their cars with no issues.
 
#36 ·
Dang it, I was shopping today for cam, long tube headers, I was told that heads need to be redone for valve drop issues, before I get started I am not going say were the shops are, they are very well established shops that back there stuff and have a very great REP.
As a bonus I was shown the heads and the problem, trust me when I say this there is a problem. My question to all you peeps, has anyone else been told they need to address this issue first.
From what I have been told by both shops its mainly on the LS7.
just send ur heads to wcch. I bought a set of heads done then sold mine. not worth the risk.
 
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