BDASSZO6

Agree with dar02081961. Thats why GM has mechanisms in place to prevent damage. The fuel shut off occurs well before a potential catastrophic event can happen. The LT4 is bullet proof. Unless you hear something, just drive the car!

timmyZ06

Ls7 is a whole is a whole different story! When mine happened it didnt really had time to overreved too far, but it happened few times! I was listening for weirds noises . Maybe i got lucky, but after the LDT was sure about no damages. Once gain, its super easy to go in 1st instead of 3rd, i dont get it!!

timmyZ06

My buddy's supra had GSC2 cams on it, when he did the same, bent all the valves right way!!

TXshaggy

There is no protection for a mechanical over rev due to a missed shift. With that being said this sounds like a minor excursion with no immediate symtons so I’d just continue to drive and be more careful.

Lucky this isn’t a Porsche which logs every overrev and would result in diminished value on sale.

BDASSZO6

Fuel shut off is not a protective mechanism?

TXshaggy

While fuel shut off will occur, the mechanical rotating drivetrain will exceed redline. If the overrev is significant it may lead to valve float and piston to valve impact.

vdavenp802

Definitely sell it NOW, and really, get an automatic, much quicker and no missed shifts...........

SGT_G

Lol if I sell it, which I won't, I'll defect to a viper.

Bill Dearborn

Jason has far more experience than a lot of people on the forum. I do know that an Over Rev that goes into the range that Jason mentioned can damage/weaken the valve springs and eventually lead to a broken valve spring which may then lead to a swallowed valve.

Bill

Katech_Zach

I'll go back to my response and use of the word "probably". "Probably" and the cost of replacing an engine don't go together for me. I would rather replace valve springs than risk it. Like I said in my instance of over-rev last year, the valve springs were within spec still. I wouldn't want to worry about it for future track days though.

FYI - even 9000rpm over-revs don't typically fail engines immediately. They can fatigue valve springs which can lead to failure later. That's why you hear people say "I was just driving down the highway and the valve spring broke", failing to mention the mechanical over-rev on the track day the weekend before. We have had 9000rpm over-revs in World Challenge engines and finished the race. When it's a sprint race and GM cared more about winning than hurting an engine they just went for it. Of course, valve springs got changed after the race if not a whole rebuild.

dar02081961

Technically what folks are saying is correct and what can happen during a "over rev".
A mechanical 'over rev" is a physical condition based on the mechanical capabilities of the valve train, the bottom end rods and rod bearings.
And all of the things you mention can occur during a "mechanical over rev".
Generally any damage done during a mechanical "over rev" will show itself within 10-20 thousand miles probably sooner. (just a swag here to make a point later).

However in this case the OP states the information available to him indicates the engine didn't exceed 6900 rpm or so.
While we all know the rev limiter on the LT4 is electronically set at 6600 rpm from the factory, we also know 6900 rpm is not really an "over rev" for an LT4 in mechanical terms.
There are a few folks in the Z06 community pushing these LT4s up to 7000 rpm without any rev related issues.
Not going to get into why they feel safe doing so but there is some solid logic behind it.

My point is the OP should have many thousands of miles of warranty left on the engine/car.
If he actually had a "mechanical over rev" (which the data suggest he didn’t) the damaged components have plenty of time to fail while he is still covered by the warranty.

I agree if you were racing this engine without the factory rev limiter and had unlimited available resources, a valve spring and lifter replacement would be in order.
But for us normal folks based on the information presented, chances are the OP can drive the car long enough under warranty to determine if he damaged the engine.

I am betting he will be just fine.

TXshaggy

^^^^I wasn’t responding to you, but rather than the poster that said these motors have rev limiting protection and to not worry.

dar02081961

Sorry, didn't mean for it to sound as if I singled you out.
Corrected.

My comments are trying to make the point the OP states in the original post the max rpm he hit was 6900 rpm.
6900 rpm is not a " mechanical over rev" for an LT4.

Katech_Zach

If it was truly 6900rpm you're right it will be fine. I was basing my engine speed calculation on 80mph in 1st gear. We're not really sure whether it actually hit that without data.

Road machine

This is why I didn't go for the M7. I loved the M6 in my 2008 Z06.......why did they get rid of it???

There is no protection for a mechanical over-rev so slow down your shifts.....if in doubt push the clutch in and let the stick go to natural neutral, which falls between 3rd and 4th. then you know where you are. Unless you are racing for pink slips the insurance this move will give you is worth it to save your motor. I would agree that there should not be any motor damage if ti still runs fine, but if you do this into a curve you will lock up and crash.

Sub Driver

Fuel cut-off will only stop you from over-revving your car while accelerating in one gear. A mechanical over-rev condition happens when downshifting. In this case, as soon as the clutch is engaged the engine will rev up on its own to match the speed it was at in the previous gear. So if you were doing 90mph in 2nd gear and immediately shifted into first the engine will rev up to wherever it needs to be to match 90mph in 1st gear. There is nothing that can prevent this once it is initiated. It can also happen so fast that the tach doesn't have a chance to register just how high it went right away.

TXshaggy

Stop manhandling the M7. 3/4 is the easiest shift since the M7 always returns to this gate on its own...gentle pressure left/right gets you into 1/2 or 5/6. Hard pressure right and up for 7th. Don’t grab the shifter..use the palm of your hand and the gate springs to guide you.

Mr. Gizmo

exactly -- It certainly takes some life out of the engine with a huge jolt to all the internals - 2nd gear at full on is 88-to 92 mph. if the OP was ***** out in 2nd and powershifted to 1st meaning to grab third -Something had to have gnashed on the inside.

Dwyer

So in your opinion damage was done to all the internals (because something gnashed on the inside) and Katech is wrong?

What qualifications do you possess to give that assessment to the OP or anybody for that matter?

SGT_G

Honestly I must not have fully releases the clutch because the tracer for the highest point you rev was at the 68-6900 point. If I was really in the 8k range, that tach should've shot hard to the right. Additionally, like I said, I wasn't redlining 2nd but rather at the higher end of it.