Noticed something interesting on my LT5...

[LGAFF]

Originally Posted by 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.

My 90 engine was rebuilt in 1993, numbers match.

[1989ZR1#74]

Originally Posted by LGAFF

My 90 engine was rebuilt in 1993, numbers match.

So the LT5 was shipped back to MM, they rebuilt it and sent it back for install. The customer had the option of a replacement LT5 to expidite the repair. So the rebuilds look the same, now we need to find a swap LT5..

[bdw18_123]

I searched through the service records that I have on the car, but I didn't find anything mentioning the LT5 getting removed and sent off for repair.

I did find the temp ID tag for the car when it was first delivered from the lot. Delivery date to the original owner from the dealer was 11/22/1990. Then on 12/13/1990, it went in to a GM dealer for service. 8 issues are listed (a heck of a lot for a brand new, couple week old car). One of them states "Engine RPM's surge badly - when coming off fwy wants to stall, nec. to throttle" and just below a tech wrote "Check & set min idle to specs", which I guess is all they did to fix the problem. I don't think re-setting the min idle to specs would fix bad rpm surging.

The next service record was on 8/14/92, so who knows what happened between those dates. One clue is a receipt from the DMV stating "Acknowledgement of Nonoperational Status" valid from 11/24/91-11/24/92, with an issue date of 11/27/91. License plate number listed on this matches my ZR-1. Weird for it to be put into Non-Op with it only being 1 year old, maybe it was during that time that the swap was done (if there was one)?

[LGAFF]

I just have a service invoice from the dealer that says "Engine Rebuild" no cost listed. I spoke to prior owner, Former CEO of Illinois Tool, and he did not remember why they redid the motor, all he recalled was that it took forever to get it back. I would be surprised if it went back to Merc Marine......car had 69K miles on it. Prior owner said it was done at no charge however.

[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.

[1989ZR1#74]

Originally Posted by 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.

Let me ask then if not MM where would it go to?

as LGAFF said " took forever to get it back" back from where?

I have read in several sources (not available to me right now) that it was what they did. The LT5 was way too complex to rebuild at a dealer.

[1989ZR1#74]

From the registries archives:

"However, the question still remains: once an LT5 problem is diagnosed as being other than with engine management, what framework is in place to acquaint dealer service departments with the revolutionary technology of the LT5? At the press introduction of the LT5 at Riverside, California last June, that question was raised. Chevrolet said that training would commence a few months before the introduction of the ZR1 and until servicing ability is up to speed, any LT5 problem requiring the opening-up of the motor will be handled with an engine exchange. The dealer will remove the offending LT5, replace it with a known-good unit then ship the bad motor to Mercury for repairs. "

http://www.zr1netregistry.com/LT5tech.htm

[1989ZR1#74]

So #2299 has an LT5 with a deviation in the MM stamp/markings, and with the BG stamp/markings. Both correcting a previous mark/stamping. It was clearly done at two seperate points of manufature 100s of miles apart. It was delivered to customer on 11/22/1990. It has a block casting date of 03/07/90. It has a documented history of being off the road for a year early in it's life. Engines, at least in the early days of the ZR-1 were shipped back to MM for repair. The only point I can not foot note right now is my belief that the customer was given the option of repair their LT5 or replacing it with an available "core" from MM.

There is nothing in what I just typed that will ensure that that did happen, but there is also nothing as of yet to prove it did not happen.

Another thought/theory, "Mary" the inmfamous BG lot driver who in 1990 was cold starting ZR-1s at WOT and grenading the LT-5s must have taken out several LT5s. What process did Chevrolet go through to replace these engines? What did they do with the damaged blocks? when did Mary stop killing LT5s? Could #2299 have started it's life with a new block because Mary killed it? That would make #2299 an interesting footnote in the lexicon of ZR-1 history. Time to order your build sheet and invoice to find out when it was built and when it was shipped. If there was a large gap maybe it was waiting to get a new LT5.

[A26B]

I just spoke with Chris Allen who was the man in charge of design & supervision of the LT5 assembly line at Mercury.

Chris said "to the best of my recollection, for the first year, dealers were not allowed to open an LT5 engine. He went on to say "I only recall one engine that was ever returned to Mercury. We opened it up and the only thing wrong with it was carbon buildup. We cleaned it up & sent it back to the dealer with no other work."

Chris also said that Mercury did not have any procedure for rebuilding LT5 engines and that he would have known about it if they did.

Apart from engineering development & test units, there appeared to be a couple of warranty replacement engines in the group of 30 engines I had that were remaining from the lot of engines GM sold off 2 or 3 years before I got them. As I understand it, what actually happened was that dealers did not rebuild LT5's. The dealer received authorization and was shipped a new crate engine from GM stock (not Mercury). The dealership returned the original engine to GM, in the same crate the new one was shipped in, where upon receipt, it was simply placed in a storage warehouse with all of these other test & development engines. The warrany replacement engines were never rebuilt as the cost to GM would have been greater than the cost of a new crate engine.

I probably have some photos of the engines I think were returned & recall some instructions to the dealer about what all to remove & return to GM. Those crates were different than the crates I've seen for crate engines offered for sale.

It seems probable to me that procedures & policies perceived to be feasible when written may have turned out in actual practice to not be practical.

[1989ZR1#74]

Good stuff Jerry, you have moved the ball forward and I learn more and more. Ok so if the block was replaced it would not have been restamped.

2 seperate issues:

So why was MM mark on #2299 restamped? The fonts on the MM restamp appear to be the same. They appear to have been done to document not to deceive (ie like a 63 Corvette Restamp) Perhaps you could send your friend the link for the picture and ask him what he thinks.

VIN stamp. This LT5 perhaps was destined for another 90 Corvette at BG but was diverted to #2299 that would explain the VIN restamp again to document not to deceive. At what point was the LT5 assigned to a ZR-1? how much time is there between assignemnt and installation?

It does not seem plausible that an outside repair shop would go through the effort to restamp the block. Nor would they have access to the correct stamps/fonts etc. So I would think this had to have originated at MM and BG.