HELP: info about early '90 cam failures - ZR-1 Net Registry Forums

ZRWON · 10-08-2009

FACT or FICTION: If my memory is correct the cause of the problem was when the very early ZR-1s cars were being loaded on the truck trailer for delivery in the winter of 1989 & 1990. The drivers would start the motor and immediately rev it up for a sprint up the ramp onto the delivery trailer. To solve the problem a 4-5 second delay in starting was programmed to allow the motor to crank long enough to get oil to the cam and eliminate the cold start loading problems.
Some of the cam problems were not evident until the car had been driven several miles. BG/GM and Mercruiser covered the LT5 replacement and/or repairs? I have #553 with an assembly date in early November with only 14K miles on it. It really runs great but it has some strange things about it that I never noticed on either of the '91s that I owned.
I often wonder if #553 was one of those problem cars from the winter of 1989-1990. Are there any records that will identify which of those early LT5s were replaced or rebuilt? Is #553 one of them?

tccrab · 10-08-2009

Page 73, Heart of the Beast, Chapter "High Tech In the Heartland"

Behan and Barton were walking in the parking area behind the plant where Corvettes were being loaded onto trailers. The weather was bone-chilling, well below freezing. They both heard the familiar whine of the Nippondenso starter motor of the LT5 as a ZR1 was being started up and then heard the LT5 go to maximum rpm-something no ZR-1 owner in his or her right mind would ever do. Benhan turned to Barton and said, "I think we've found our problem". He walked over to the young woman starting the cars, introudcted himself and asked her if she started all the cars that way. She said yes.
<snip>
.......It ended up that some cam journals were out of spec. Also, CPC had shortened the engines crank to start time without informing Lotus or MerCruiser. Each cam from a failed engine was checked at an independent laboratory. We caught all the cars with this problem at Bowling Green. One got to a dealer, but we caught it before it was sold. We made changes to our tolerences, Bay City tightened up it's quality control, and a rev limit was set on the engine in a cold start situation.

No mention of any cars that may or may not have failed after being sold. Or if it was cam failure related.

Early in '90-91 Chevy techs weren't allowed to disassemble a LT5. If there were internal problems, the engine was removed intact and shipped back to Bowling Green. A replacement motor was sent in exchange. Ron Hassleman had a storage unit full of prototype motors and "take-out" motors a few years ago that he eventually sold. Maybe he kept a list of the serial numbers of the motors he had.
Where did those engines all wind up anyway? I was really surprised that parts and pieces didn't show up on eBay or here on the registry. Did the new owner send them off to Area 51 or to that warehouse where Indiana Jones found the Ark of the Covenant?

Have you ever looked to see if the serial numbers match on the heads and the block?
The '90 is the most different of all the LT5's. What about yours makes you suspicious?

TomC
"Crabs"

scholtmj · 10-09-2009

I believe it was actually 1991 when the problem came up. Like the HOTB states, none of the suspect motors were sold to the public.

On that other forum I got flamed for quoting the HOTB and saying it was cam journal tolerances, not the starting method. Yikes

10-08-2009	#1
ZRWON Join Date: Jun 2005 Location: Whidbey Island WA Posts: 258	HELP: info about early '90 cam failures FACT or FICTION: If my memory is correct the cause of the problem was when the very early ZR-1s cars were being loaded on the truck trailer for delivery in the winter of 1989 & 1990. The drivers would start the motor and immediately rev it up for a sprint up the ramp onto the delivery trailer. To solve the problem a 4-5 second delay in starting was programmed to allow the motor to crank long enough to get oil to the cam and eliminate the cold start loading problems. Some of the cam problems were not evident until the car had been driven several miles. BG/GM and Mercruiser covered the LT5 replacement and/or repairs? I have #553 with an assembly date in early November with only 14K miles on it. It really runs great but it has some strange things about it that I never noticed on either of the '91s that I owned. I often wonder if #553 was one of those problem cars from the winter of 1989-1990. Are there any records that will identify which of those early LT5s were replaced or rebuilt? Is #553 one of them? __________________ ZRWON '90 #553 & BEAST2 '93 #211, an AutoMasters Street Skinner version of a BlackWidow LT5 [URL]http://www.zr1netregistry.com/ZR1_faq.htm#66[/URL] NCRS#894 "It's not the car; it's the people" ...Doug Johnson 1953-2003 40 years VETTE history @ [URL="http://home.comcast.net/~bbstrow/"][COLOR=#555555]http://home.comcast.net/~bbstrow/[/COLOR][/URL] [URL="http://www.youtube.com/watch?v=p21dz80uGaA"][COLOR=#333333]http://www.youtube.com/watch?v=p21dz80uGaA[/COLOR][/URL]

10-08-2009	#2
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,654	Re: HELP: info about early '90 cam failures Page 73, Heart of the Beast, Chapter "High Tech In the Heartland" Behan and Barton were walking in the parking area behind the plant where Corvettes were being loaded onto trailers. The weather was bone-chilling, well below freezing. They both heard the familiar whine of the Nippondenso starter motor of the LT5 as a ZR1 was being started up and then heard the LT5 go to maximum rpm-something no ZR-1 owner in his or her right mind would ever do. Benhan turned to Barton and said, "I think we've found our problem". He walked over to the young woman starting the cars, introudcted himself and asked her if she started all the cars that way. She said yes. <snip> .......It ended up that some cam journals were out of spec. Also, CPC had shortened the engines crank to start time without informing Lotus or MerCruiser. Each cam from a failed engine was checked at an independent laboratory. We caught all the cars with this problem at Bowling Green. One got to a dealer, but we caught it before it was sold. We made changes to our tolerences, Bay City tightened up it's quality control, and a rev limit was set on the engine in a cold start situation. No mention of any cars that may or may not have failed after being sold. Or if it was cam failure related. Early in '90-91 Chevy techs weren't allowed to disassemble a LT5. If there were internal problems, the engine was removed intact and shipped back to Bowling Green. A replacement motor was sent in exchange. Ron Hassleman had a storage unit full of prototype motors and "take-out" motors a few years ago that he eventually sold. Maybe he kept a list of the serial numbers of the motors he had. Where did those engines all wind up anyway? I was really surprised that parts and pieces didn't show up on eBay or here on the registry. Did the new owner send them off to Area 51 or to that warehouse where Indiana Jones found the Ark of the Covenant? Have you ever looked to see if the serial numbers match on the heads and the block? The '90 is the most different of all the LT5's. What about yours makes you suspicious? TomC "Crabs" __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B] Last edited by tccrab; 10-09-2009 at 12:06 AM.

10-09-2009	#3
scholtmj Join Date: Nov 2008 Location: Grand Rapids, MI Posts: 384	Re: HELP: info about early '90 cam failures I believe it was actually 1991 when the problem came up. Like the HOTB states, none of the suspect motors were sold to the public. On that other forum I got flamed for quoting the HOTB and saying it was cam journal tolerances, not the starting method. Yikes