jta98z

Hey guys. Been doing some research in preparation for getting my heads fixed. Not sure if this is just an anomaly or an actual cause and effect. What I've been looking for is moderate to high mileage cars that haven't had engine trouble and taking note of any differentiating factors. One thing I seem to have noticed is many of these problem free cars are very lightly modded. Intake and tune only etc. And it seems like most of the failures I read about were on either bone stock cars or cammed cars.

Is there any way possible a tune helps minimize wear or is this all just a coincidence? I know there was that poll a while back on failures and the bone stock cars failure poll double the failures of the intake and tune cars. But I know that should be taken with a grain of salt because there are many more people with stock cars to respond to the poll than intake and tuned cars.

Idk. I'm just rambling. Does any of this stick with anyone else?

Road machine

My car is bone stock except for mild to wild switch. Although I don't have lots of miles (15k) I drive it hard and have had no issues at all. One thing I always do is let the car warm up well before any high revs or hard acceleration. I use the oil temp as a my guide as that more closely will reflect block temp. I always wait till the oil is over 100 degrees, before getting on it at all. The tolerances on the LS7 are very tight, and the engine is designed to run at temp. Hopefully my engine won't blow up next time I start it after saying all this.

AZDANZ06

Nope, it is the fact that a percentage of heads were machined correctly and a percentage of them were not, my bone stock 2008 with 27K had 4 exhaust out of spec, 2 intake out of spec, and the rest were all on the borderline of being in/out spec. Get them checked and fixed if necessary

I just wrote a review on American Heritage Performance who re-did my heads and is doing all the R&R work in there shop:

https://www.corvetteforum.com/forums...post1588709256

Mark2009

No.

Z06_1

Cylinder wall wear is another story - an excessively rich tune can wash the oil film off the cylinder walls, dilute the oil, and create some other nasty side-effects.

Michael_D

Tuning could cause damage, but it's not a cause for guide wear.

Chiff

I have a 06 z with 50k on the clock ., nd it runs smooth with no problems at all ., nd never have had the valves checked., car is also stock

Johnjan

Could also be that Owners with tunes are arguable more "enthusiastic" than Owners with bone stock cars. Therefore, a more "enthusiastic" Owner is more likely to post about his car.

Until ALL Z06's are accounted for, meaning even those Owners without a presence on this forum, any statistical analysis or prediction of whether one car or another is going to have problems is worthless.

Your mileage may vary of course...

Hib Halverson

First, we have to define "tuning" with respect to the LS7 engine controls.

Most "tuners" will evaluate the stock calibration as: "rich at WOT."

The reason GM cals rich at WOT is to lower combustion temperature because:
1) reduce emissions–lower combustion temperatures reduce NOx emissions
2) reduce the possibility of detonation–lower combustion temperatures tend to not detonate as much
3) reduce exhaust valve temperature.
4) insure the engine will not be lean if the owner uses oxygenated fuel (ie: E10 ethanol blended gasoline)

The conventional wisdom amongst many tuners is to lean out the AFR at WOT to eliminate the over rich condition and gain the modest extra performance which comes with that.

As to the question: does "tuning" cause guide wear?

I think the answers are "Probably not" or "Yes"

If the cylinder heads' stem-to-guide clearances are within production tolerances (.001-.0026-in.) and no non-concentricity of guides and seats is present, leaning out the WOT AFR somewhat will probably not wear the guides excessively as long as you don't go more lean that about 12.6:1 for gasoline and 12.2:1 for E10.

If the cylinder head's stem clearances are already beyond production tolerances and are nearing or exceeding the service maximum of .0037-in. and guide wear is occurring due to non-concentricity of guides and seats, then, yes, tuning, such that the WOT AFR is more lean, will likely make the guide wear problem worse by accelerating the wear rate. When the guides wear, the heat transfer path between the stem and guide is obstructed which overheats the exhaust valve. If you change the AFR at WOT such that higher combustion temperature causes the exhaust valve to run even hotter, a corresponding, further increase in the rate of wear will likely occur.

0Anthony @ LGMotorsports

I don't think there is enough info out there across the entire production run of the cars to know that for sure.

My car had 70k miles on it when I sold it and did show some signs of wear but was not out of spec....at the same token I had seen 08 cars (same as mine) fail less than 10k miles.

FWIW my car was intake, tune only.