Background:
99 WS6 154k miles. decided to pull the motor and freshen it up. New rings, mains/rod bearing and cam bearings. While there put in the GMPP ASA cam with new lifters, push rods, and springs. had the trunion upgrade already.

On first start of motor I had good oil pressure. Ran it for 30-40 minutes while bleeding the coolant and tuning it to idle. held oil pressure the whole time. no odd noises. Went to park it and the motor instantly stopped while at approximately 1500 RPM. Again no noises, putter, nothing. just stopped like it hit a wall.

With a breaker bar, the crank would move about 5 degrees each way in rotation then I could not spin it further. eventually by luck it freed up while trying to spin it backwards. This was all with the plugs out. Since then it has spun freely.

Took motor out. Found that there is significant scoring and ground in of the back of the cam gear, both sides of the cam retainer plate and the front surface of the cam where it hits the retainer plate.
With rockers off and the cam gear off it will spin freely and move in and out freely. When I fut just the cam gear back on it will only spin with the ratchet but freely and it does not move in and out even a little.

things that were changed in relation to the cam:
- cam bearings
- retainer plate (victor reinz flat style like original - not recessed)
- upgrade to ls7 chain only
- cam
- lifters

Things not changed:
- cam gear

Please note that the old retainer plate has no wear at all.
Measured the snout on both cams and there was 0.0005 difference and the new cam snout measured the same around the circumference (not cut at angle). Cam bearings look like there were a few high spots that wore down.

Anyone have ideas as to what caused this much wear in less than an hour of running? And caused the motor to lock up?

is it an oiling issue with the plate? a cam problem? something else?
Thank you in advance

outside of retainer plate:


back of cam gear:


back of retainer plate:


old vs new retainer plate:


asa cam:

 

My cloyes ls2 timing set had a needle thrust bearing that went between the cam gear and retainer plate. Was the gear on the crank pressed on far enough so they were perfectly aligned?

 

What's the thickness of the New junk plate Vs. Old Oem plate?

 

they measured the same.

I have a new plate and gear coming and I'm going to check cam end play. Also going to check with cam out and gear bolted to it to see if there is any clearance to the plate.

 

Are all the cam bearings lined up properly in relation to the oil gallery hole? Does it appear any of them spun?

 

We used a camera to look at all the bearings (trying not to take motor apart and start all over again). they all appear lined up correctly.

now unless they had spun when it locked up and I somehow spun them back perfectly when I got it to unlock....

 

I am reaching for anything logical as I have never seen this type of failure before.

I am intrigued to find the root cause.

 

So you don't think there is metal all through the motor?

 

You say the snout length was within .0005 of the other cam.

Was it measured before or after the failure? Is it .0005 larger or smaller than the old cam?

 

measured after failure on the cleanest areas on the snout. Paper is not in front of me but I believe the new one was larger.


It seems like there was no oil to those surfaces but I never lost oil pressure.

 

at this point I am looking for ideas about the cause. if I can't find a cause its all coming back apart for new cam bearings and cam again as well as pulling all the pistons and looking at the bearings and rings. that means the heads come back off. If I can find a cause I can just pull the oil pan and not have to completely disassemble .

 

This:
And how much crank endplay did it have...?

 

as far as I can tell the sprockets are lined up correctly. I will measure the crank endplay tonight.

 

Pretty crazy, I've never seen wear that bad on the thrust plate before.

 

update.
with new cam gear and gm retainer plate the cam end play was 0.0015 which is the minimum spec. I took the cam gear to a machinist friend. runout on gear was 0.001. He took the mating surface of the gear to plate down some. end play is now 0.0052.
I am going to try this.

crank end play was 0.0035 also in spec.

does anyone have picture of the original cam gear from post 1 from the back side? the new gear has slots cut into it:

 

This is the stock gear off my 1999 TA.

 

thank you for the picture.

 

so far it is working. I ran it for a few hours yesterday and it made no weird noises and didn't lock up.

 

Do an oil change yet?

 

Happy to hear it. Did you ever find anything?