Noticed something interesting on my LT5...

[bdw18_123]

I was in the garage tonight looking at the numbers on my '90 LT5 that I have on an engine stand and noticed something interesting.

The Mercury Marine numbers stamped on the oil-pan flange, driver's side look like the last part of the "10ZSH..." number was ground out and redone. Mercury Marine stamped the "10ZSH..." number, right?

Apparently, they didn't completely grind out the mistake, you can see very faintly that the end part of the previous number said "X0052299". They must have accidentally stamped the last 4 digits of the VIN instead of the "0001" that was supposed to be there. So Mercury Marine knew the VIN's of the cars that each engine was going in?

Here a picture of the driver's side oilpan flange showing the number:


Then I noticed that the VIN stamp that GM puts on was also re-done (what a coincidence, GM & Mercury Marine both screwed up their stamps on the same engine!). The passenger side transmission-mount flange of the LT5 where the VIN stamp usually is, is stamped out with "X"-type things.

Here is a picture of it:


Reading this from the ZR-1 Net Registry site explained that one:

"GM NEVER re-stamps an engine except for one reason which we will mention below. First, let's discuss the stamping process:

VIN numbers are put into a handle, then stamped on the right rear of the engine, where there is an upright portion. This stamping was done at the third station on the transmission line when the trans was attached to the LT5. Both the trans and the engine were stamped with the same stamp. As this was done manually, there is a chance that a mistake could be made. Sometimes the stamp wasn't changed after a previous stamp was made, maybe the L98 engine stamp was used mistakenly on a LT5. After all, they were both coming down the same line, a ZR-1 no closer than one every three units (there had to be 2 vehicles between each ZR-1 for assembly time purposes).

After the stamping process, the next station performed a quality control inspection, verifying the VIN stamped matched the build sheet. If a problem is discovered, there were alternate locations for a re-stamp. After the wrong VIN was XXXX'd out, the correct stamp was made on the opposite side of the engine, near the same place. Same with the trans."

The correct VIN was then re-stamped on the driver's side flange (the "9's" are hard to see, but they are there):


The transmission VIN stamp is the correct "1L5802299" though and is not "X'd" out so the LT5 must have gotten stamped before the transmission.

Just thought that that was interesting, so I thought I'd post it up. Anyone else find re-stamps on their LT5's?

Thanks, I'll have to check mine out from curiosity now since my block is on the stand too.

[ZR1Vette]

Interesting... where exactly is the stamp "driver's side oil pan flange" and is it visible without the engine removed?

When I was down at BG watching my C6 being assembled went over the the engine assembly area (meaning the engines sans accessories and drive train that come from the engine manufacturing facility are mated to accessories) the VINs are all computer/bar coded generated and then a device is placed in the correct location of the engine and 'engraves' the number...no stamping or human involvement (other than placing the 'engraver' on the engine)... at the same time elsewhere in the assembly plant a device is 'engraving' the chassis with the same VIN.

[1989ZR1#74]

Another possibility is the engine was a MM remanufacture swap. Do you know the entire history of the car? Like you said, what are the odds?

How does 3/07/1990 engine cast match with your build date?

[Ccmano]

Originally Posted by 1989ZR1#74

Another possibility is the engine was a MM remanufacture swap. Do you know the entire history of the car? Like you said, what are the odds?

How does 3/07/1990 engine cast match with your build date?

Sounds about right time frame wise. My 90' is sn#1723 with a casting date of 2/15/90. No cross outs and engine is original to the chassis.
H

[bdw18_123]

Originally Posted by ZR1Vette

Interesting... where exactly is the stamp "driver's side oil pan flange" and is it visible without the engine removed? ...

It's on the flange of the block on the driver's side just above the oilpan. It's a number stamp that Mercury Marine stamps on at the time of engine manufacture. It would probably be very hard to see it with the engine installed, the exhaust manifold would be in the way.

Here is a pic of the driver's side of my LT5 with the driver's head removed to give you an idea where the MM stamp is at (ignore the red dots at the top, was a mistake ):

Originally Posted by 1989ZR1#74

Another possibility is the engine was a MM remanufacture swap. Do you know the entire history of the car? Like you said, what are the odds?

How does 3/07/1990 engine cast match with your build date?

What exactly is involved with a "MM remanufacture swap"? I don't know what the build date of my car is, is it on the build sheet or do you have to calculate it somehow?. There was no build sheet on my gas tank, however I did pull the one out of the front crossmember. Lots of it is unreadable though, I need to get a copy from the NCM.

Here is a pic of the buildsheet from the crossmember:


As for the history of my car, I do have a carfax printout (I know that doesn't tell you a whole lot) and also a bunch of service records from the early ninties. The guy I bought the car from, bought it new, so I am only the 2nd owner.

The first record that the Carfax shows is an emissions inspection report with a date of 12/30/1993. There are no records before that. The PO did mention that the car had been sitting at the dealership for awhile, so maybe that's why there's no records before '93?

[1989ZR1#74]

Originally Posted by bdw18_123

It's on the flange of the block on the driver's side just above the oilpan. It's a number stamp that Mercury Marine stamps on at the time of engine manufacture. It would probably be very hard to see it with the engine installed, the exhaust manifold would be in the way.

Here is a pic of the driver's side of my LT5 with the driver's head removed to give you an idea where the MM stamp is at at (ignore the red dots at the top, was a mistake ):

Well it is a Friday Mistakes happen.

[1989ZR1#74]

The LT5 was not serviceable at the local Chevy dealer. If there was a problem with the engine they would pull it and send it back to Oklahoma and have MM rebuild it, or the customer could opt for a replacement MM LT5. I was thinking outloud that perhaps this ZR-1 had it's engine replaced by MM under warantee. And the factory numbers reapplied. The bad LT5 would then be rebuilt and placed in inventory for a future replacement. I have never seen a replacement LT5, but I would imagine the markings would deviate from standard production practice. Since, as you point out, the likelyhood of both MM and BG making a mistake is rather low, it should be considered. It would be the equivalent of a CE block in C2/C3 corvette world.

[rhipsher]

Must of been a Friday car.

[A26B]

I have friends at Mercury who were core personnel in the LT5 program. I'll ask them about rebuilds @ MM. Frankly, I would be very surprised if any engines were rebuilt at MM.