[Z06] What are the stock LS7 valve guides made of?
#1
Le Mans Master
Thread Starter
What are the stock LS7 valve guides made of?
Just curious what the stock valve guides are made of and if excessive wear was occurring would it show up in an oil analysis as an elevated metal reading?
U.M.
U.M.
#2
Safety Car
sintered iron alloy - and the idea is that your iron levels would be elevated but I'm not aware of any direct correlation between oil analysis and guide wear.
FWIW my oil analysis showed slightly elevated iron levels above universal averages, but the next owner pulled the heads and found the guides to all be well within spec.
You also have to allow for the possibility that the guides could coming out-of-spec from production ,versus acutely wearing down during normal driving over a few thousand miles.
FWIW my oil analysis showed slightly elevated iron levels above universal averages, but the next owner pulled the heads and found the guides to all be well within spec.
You also have to allow for the possibility that the guides could coming out-of-spec from production ,versus acutely wearing down during normal driving over a few thousand miles.
Last edited by Random84; 09-28-2012 at 07:38 AM.
#3
Le Mans Master
Thread Starter
My last few oil analysis have shown increasing levels of iron... above the industry averages for LS7's they've received samples from. The car is not tracked. Could this be an indicator my guides are wearing?
U.M.
U.M.
#4
Unless your valve seals are leaking oil does not get onto your valve guides.
And if your valve seals are leaking, then you'll start seeing smoke and using oil.
In a normal situation the iron from your guides will never make it into your motor oil. Smoking at startup though would give you an indication that something was up.
But unless your valve seals are leaking, the worn iron from your guides, is more likely to end up in your exhaust system. That is until the guides wear enough to compromise the seals and you start getting smoke on startup from oil making it into the combustion chambers.
Bottom line is motor oil, and the type you use, is not going to solve the valve guide wear issue and a Blackstone oil analysis is not going to tell you much of anything about valve guide wear.
Take a look at the posts by CGZ06, whose motor in his 2009 just popped yesterday coincidentally, when it broke an exhaust valve and an intake valve.
http://forums.corvetteforum.com/c6-z...post1581583974
Last edited by '06 Quicksilver Z06; 09-28-2012 at 08:30 AM.
#5
Well, read 'em and weep boys. Anything over .0037" is out of spec. Howie's iron, according to the reports, has been looking good the whole time, and most of his exhaust guides guides, and some of his intake guides, are out of spec.
Anybody who was hoping that motor oil and oil analyses were going to help in keeping an eye on this matter, can now let those thoughts go.
I'm looking at what they tell Howie in the "comments" on this last one done in December of 2012, about a month before he pulled the heads on the car:
http://forums.corvetteforum.com/c6-z...rack-days.html
http://forums.corvetteforum.com/c6-z...bil1-0w40.html
http://forums.corvetteforum.com/c6-z...ent-motor.html
Anybody who was hoping that motor oil and oil analyses were going to help in keeping an eye on this matter, can now let those thoughts go.
http://forums.corvetteforum.com/c6-z...rack-days.html
http://forums.corvetteforum.com/c6-z...bil1-0w40.html
http://forums.corvetteforum.com/c6-z...ent-motor.html
Last edited by '06 Quicksilver Z06; 02-27-2013 at 10:16 PM.
#7
Originally Posted by SKF Sealing Solutions GmbH
Valve stem seals are devices that are engineered to allow a small amount of oil to pass through their lips (oil-metering) to lubricate the valve stem / valve guide interface of an engine (see figure 01).
If too much oil passes through the lip of the seal, emissions are worsened and coke builds up on the valve, potentially causing the engine to lose power or even fail. If too little oil passes through the lip of the seal, the valve does not receive enough lubrication and will scuff, which ultimately will cause the valve to seize. The ideal metering rate lies between these two extremes.
http://www.skf.com/files/867381.pdf
If too much oil passes through the lip of the seal, emissions are worsened and coke builds up on the valve, potentially causing the engine to lose power or even fail. If too little oil passes through the lip of the seal, the valve does not receive enough lubrication and will scuff, which ultimately will cause the valve to seize. The ideal metering rate lies between these two extremes.
http://www.skf.com/files/867381.pdf
#8
Race Director
DH's experience is probably the most on the spot example for this question!!!! You couldn't ask for more data on this. He has been doing the oil testing since the new engine and posting the info in here. He then pulls the heads and has just about every guide out of spec..........
#10
DH's experience is probably the most on the spot example for this question!!!! You couldn't ask for more data on this. He has been doing the oil testing since the new engine and posting the info in here. He then pulls the heads and has just about every guide out of spec..........
As Quick noted, that stuff is probably going to get blown out the exhaust pipe.
#11
DH's experience is probably the most on the spot example for this question!!!! You couldn't ask for more data on this. He has been doing the oil testing since the new engine and posting the info in here. He then pulls the heads and has just about every guide out of spec..........
His "geometry" was good too, and his guides are shot.
You know, I was just thinking about you Mark.
You still have the rest of my old stock OEM exhaust valves that I sold you?
Do you want to buy the springs that came with them?
I'll cut you a good deal on them, same as I did the used exhaust valves. Shoot me a PM if you are interested.
Last edited by '06 Quicksilver Z06; 02-28-2013 at 12:01 AM.
#12
Burning Brakes
#13
Burning Brakes
I just got new heads from GM under warranty and the heads arrive to the dealer raw, not assembled. The gm service advisor said the guides looked like they were bronze, but a magnet stuck to them. Do the sintered iron guides look like bronze or has gm changed something?
#14
Rockin, I don't think Bronze Guides have ever come out of the LS7 heads from the factory or dealership. There might be some confusion from the service advisor, but if indeed bronze, I'd have to wonder if GM caught onto something...
#15
Le Mans Master
I just got new heads from GM under warranty and the heads arrive to the dealer raw, not assembled. The gm service advisor said the guides looked like they were bronze, but a magnet stuck to them. Do the sintered iron guides look like bronze or has gm changed something?
#17
Team Owner
#20