Lifter failure cause determined!
Thread Starter
Instructor
Joined: Jun 2006
Posts: 172
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From: Seattle WA
Lifter failure cause determined!
After 500 miles on my rebuild I ended up with 3 turned lifters and several flared ended lifters. I've finally determined the cause. It's not an issue with the lifters, rods, rockers, pre-load, or any of the things I was suspecting.
What I noticed was that on all of the flared lifters one edge of the side of the end of them appeared nicked. I figured this was the result of the flaring, but I also noticed that they didn't appear to be rolling dead center on the cam lobes. The edges of the lifters were dangerously close to the adjacent lobe. I then took a screw driver and tried to slide the cam side to side. It moved!
I determined that the cam can move towards the back of the engine (but NOT past the correct location towards front). I'm not an expert but what this says to me is that the cam thrust plate is in place (cam can't move to the front), but whatever holds the cam from going to the back isn't doing it's job. I assume that he bolted on cam gear keeps the cam from going towards the back. When I reinstalled the cam gear I torqued to spec with red locktite, could the bolts have walked out? I don't want to start tearing into the front of the engine until I figure out the possible causes.
What I noticed was that on all of the flared lifters one edge of the side of the end of them appeared nicked. I figured this was the result of the flaring, but I also noticed that they didn't appear to be rolling dead center on the cam lobes. The edges of the lifters were dangerously close to the adjacent lobe. I then took a screw driver and tried to slide the cam side to side. It moved!
I determined that the cam can move towards the back of the engine (but NOT past the correct location towards front). I'm not an expert but what this says to me is that the cam thrust plate is in place (cam can't move to the front), but whatever holds the cam from going to the back isn't doing it's job. I assume that he bolted on cam gear keeps the cam from going towards the back. When I reinstalled the cam gear I torqued to spec with red locktite, could the bolts have walked out? I don't want to start tearing into the front of the engine until I figure out the possible causes.
Former Vendor
Joined: Feb 2004
Posts: 9,615
Likes: 13
From: Burlington NC
Yes the cam bolt-retainer plate bolts could have came lose. Or when the camshaft was made there could have been a bit of extra play in the front of the cam. There is a shim that you can use to suck up some of the end play. I have seen a couple cam retainer plates that have gone south very fast from not enough end play, or not the right lube in there during break in.
I don't know if you have looked in the front end of a LS engine. But it's pretty simple, camshaft, retainer and timing chain sprocket.
Randy
I don't know if you have looked in the front end of a LS engine. But it's pretty simple, camshaft, retainer and timing chain sprocket.
Randy
Instructor
Joined: Dec 2005
Posts: 248
Likes: 31
From: TN
I feel your pain.
I had the same thing happen on a new LS3 crate motor. I changed to a three bolt cam and torqued to GM spec sheet I found online. Turns out the spec sheet was wrong. The cam gear bolts should be torgued to 26 ft lbs. The spec sheet I used had the spec at 18 ft lbs.
The cam bolts backed out and cam walked back which took out the lifters and cam. The short block was destroyed as the metal from the cam and lifters went everywhere. Metal on the piston skirts wiped out the bores on four cylinders. I could not beleive the amount of metal in the pan.
Were you using a three bolt core and what torgue spec did you use?
DJ
I had the same thing happen on a new LS3 crate motor. I changed to a three bolt cam and torqued to GM spec sheet I found online. Turns out the spec sheet was wrong. The cam gear bolts should be torgued to 26 ft lbs. The spec sheet I used had the spec at 18 ft lbs.
The cam bolts backed out and cam walked back which took out the lifters and cam. The short block was destroyed as the metal from the cam and lifters went everywhere. Metal on the piston skirts wiped out the bores on four cylinders. I could not beleive the amount of metal in the pan.
Were you using a three bolt core and what torgue spec did you use?
DJ
Thread Starter
Instructor
Joined: Jun 2006
Posts: 172
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From: Seattle WA
The car already had an aftermarket cam in it with the stock gears. I was replacing the chain only in this part of the rebuild. I followed the torque linked from the FAQ section of the C6 area. It says 18 lb/ft.
http://forums.corvetteforum.com/c6-c...tions-new.html
It seems like this is wrong and the correct value is 26 lb/ft. It would seem that RPOWU8 also used this value and lost an engine to it. I may as well.
Once I tear things down and get in there I'm expecting that those bolts will have backed out.
http://forums.corvetteforum.com/c6-c...tions-new.html
It seems like this is wrong and the correct value is 26 lb/ft. It would seem that RPOWU8 also used this value and lost an engine to it. I may as well.
Once I tear things down and get in there I'm expecting that those bolts will have backed out.
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Thread Starter
Instructor
Joined: Jun 2006
Posts: 172
Likes: 0
From: Seattle WA
According to this thread on another forum they concluded that 18 lb/ft is correct for the three bolt LS2. (26 lb/ft is for the LS1)
http://www.ls1gto.com/forums/showthread.php?t=220565
Assuming that I didn't make a mistake with the locktite or the torque wrench, the only other possibility is that the bolts were not cleaned well enough before going back in...
http://www.ls1gto.com/forums/showthread.php?t=220565
Assuming that I didn't make a mistake with the locktite or the torque wrench, the only other possibility is that the bolts were not cleaned well enough before going back in...
Instructor
Joined: Dec 2005
Posts: 248
Likes: 31
From: TN
They didn't use a different size bolt on the LS2 cam. Bolt stretch is dependant on bolt size, material, and torque. Having the proper bolt stretch is critical to keeping things together. My crate motor last about 500 miles before it ate itself. I feel that someone at GM just transposed the numbers when creating the torgue spec sheet.
You can look up recommened torque by fastener size on the net. Unless they use a totally different bolt, the proper torque should be a least 26 lb ft.
I bought ARP bolts and torqued them down to 28 ft lbs with red loctite this time.
What do some of our engine builders think?
DJ
You can look up recommened torque by fastener size on the net. Unless they use a totally different bolt, the proper torque should be a least 26 lb ft.
I bought ARP bolts and torqued them down to 28 ft lbs with red loctite this time.
What do some of our engine builders think?
DJ
Instructor
Joined: Dec 2005
Posts: 248
Likes: 31
From: TN
I am comfortable with the increased torque and the red locktite this time. I would prefer old school hex head bolts with bend over tabs.
I was amazed to see how much the cam bolts backed out but were still spinning the cam. It had pulled the pin out of the cam as well, found it in the pan.
DJ
I was amazed to see how much the cam bolts backed out but were still spinning the cam. It had pulled the pin out of the cam as well, found it in the pan.
DJ
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
My friend GTODoug lost an engine the same way with the cam bolts backing out. Same symptoms. I bet you found your cause. I'd ask him to chime in but with 2 kiddos he's now on the G8 GXP boards! Cool car by the way.
If I recall correctly and I hate to mention this, but I think he broke a couple of lifter bores in the block too. So check yours.
Seems Loctite is the key.
If I recall correctly and I hate to mention this, but I think he broke a couple of lifter bores in the block too. So check yours.
Seems Loctite is the key.
Last edited by Joe_G; Feb 12, 2010 at 06:28 AM.
Pro
Joined: Nov 2006
Posts: 667
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From: Eagle River Alaska
I did my cam install according to LS1Howto: C5 Heads/Cam Swap, Part 4: Installing the new cam, count eight pictures down on the left states in this section “Now bolt the cam gear to the cam using the old 3 10mm bolts, again, placing locktite on the threads. These should be torqued to 26lbft.”
No issues.
Sorry to hear that you are having these issues.
My 07 had one camshaft sprocket bolt in it. Something I never saw before. This was only for 2007. I had to do some triple checking research about the torque specs for a three bolt camshaft sprocket.
No issues.
Sorry to hear that you are having these issues.
My 07 had one camshaft sprocket bolt in it. Something I never saw before. This was only for 2007. I had to do some triple checking research about the torque specs for a three bolt camshaft sprocket.
Advanced
Joined: Feb 2008
Posts: 66
Likes: 1
I can't remember what I torqued mine too, you can run em pretty tight, Thing is most torque wrenches struggle to get accurate readings that low and most people actually torque past the figure. I can remember reading 18 foot pound, and I am sure I torqued to 25-26, The rocker bolts are 22 I think I used the same setting plus a bit more lol. Anyway I lock tight the cam retainer plate. I dab some 243 loctite on them as 262 will pull the thread out on ally, On the cam I usually use plenty of the blue stuff and I have never had them come loose. Loctite and new bolts are important in this area.
I use a double row with torrington bearing.
If you have a bearing in there did you drill a small hole in the retainer plate to lube the bearing?
I use a double row with torrington bearing.
If you have a bearing in there did you drill a small hole in the retainer plate to lube the bearing?
Thread Starter
Instructor
Joined: Jun 2006
Posts: 172
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From: Seattle WA
Finally had a chance to get the front cover off. The cam bolts were loose and had backed out about 1/4in. They did have locktite on them but I'm fairly sure that they should have been cleaned better and torqued down more.
Final damage:
Several lifters nicked up on the edge due to adjacent cam lobe hitting.
1 lifter turned slightly and worn.
1 lifter turned completely with end destroyed.
1 scored lifter bore from removal of destroyed lifter.
A couple of cam lobes show slight wear.
Cam lobe of destroyed lifter is heavily worn/damaged.
The brand new C5R timing chain might be shot.
The cam bearings might also be in bad shape.
Possible next steps:
The lifter bore seems to be ok after a very light sanding.
Lifters can be replaced.
Cam can be replaced (and hope that the bearings are ok?).
Timing chain can be replaced (or hope that it's ok?).
The other option is to just give up on the motor, but that just seems like overkill...
Final damage:
Several lifters nicked up on the edge due to adjacent cam lobe hitting.
1 lifter turned slightly and worn.
1 lifter turned completely with end destroyed.
1 scored lifter bore from removal of destroyed lifter.
A couple of cam lobes show slight wear.
Cam lobe of destroyed lifter is heavily worn/damaged.
The brand new C5R timing chain might be shot.
The cam bearings might also be in bad shape.
Possible next steps:
The lifter bore seems to be ok after a very light sanding.
Lifters can be replaced.
Cam can be replaced (and hope that the bearings are ok?).
Timing chain can be replaced (or hope that it's ok?).
The other option is to just give up on the motor, but that just seems like overkill...
