Uncle Meat

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.

Random84

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.

Uncle Meat

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.

'06 Quicksilver Z06

No.

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

'06 Quicksilver Z06

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

Jawnathin

Wet cardboard.

Mark2009

WhiteDiamond

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..........

Chonger

U.M

Do you have any other signs something may be wrong?

Excessive valve train noise?

Smoke at start-up?

Oil consumption?

Have you checked your plugs for oil?

Mark2009

Yeah, it was pretty much a long shot but this does clearly show that, at least in the initial and middle stages of wear, nothing is going to show up in the oil analysis. Probably nothing in the terminal phase as well (.010 and up).

As Quick noted, that stuff is probably going to get blown out the exhaust pipe.

'06 Quicksilver Z06

Yup.

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.

clogan

They're actually made of macaroni...you know, hollow stemmed and all.

rockinSeat

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?

Jawnathin

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...

jimman

It's not just iron, it has a percentage of copper and other elements to meet their recipe. Copper as you know is the fundamental element of Bronze and used in this mix to enhance thermal conductivity.

EX1

From my expierence after these past few weeks, the stock guides hold up about as well as ultra thin condoms.

93Polo

So you're safe right?

EX1

My son was born 4 months ago

2k Cobra

Since his are among the few "Good Ones", GM should buy them back to find out what they did right.

Mark2009

Perhaps you have excessive clearance... try a smaller size?