[QUOTE=SethU;19475361]A lot of assuming takes place in internet diagnostics. It's very difficult to get every little detail.

Here's my assumptions:
The springs are (actually and factually) as specified and provided by the cam manufacturer
The springs are installed at least reasonably close to their specified installed height
All of the cam lobes are within spec
The piston to valve clearance was, in fact, accurately measured on one cylinder
The block wasn't decked and the heads weren't surfaced after checking piston to valve clearance (Pretty sure you'd know that)
The cam was checked with a degree wheel
The cam was installed straight up, not advanced (or retarded)
The cam was not advanced after checking piston to valve clearance
The engine could easily be turned over manually
The engine cranked over normally
The engine idled smooth
The engine ran fine up to 4300 RPM
The engine didn't exhibit any odd noises prior to it shutting down

Is any of that incorrect?


That all sounds on the money to me. I will get it out, onto a stand, drop its pants and push the two stuck lifters thru, maybe we will learn more

 

So got on the stand and pulled sump off and so on, but I've got what I think is a very big problem. I can't get the cam past the stuck lifters! I have pulled them up as much as possible and thought sweet just twist the cam past them, but of course I forgot about the bearings on the cam and it hits the lifters by a few mm what shall I do?

 

Well it's midnight, I've I had a win and a loss. I tipped engine upside down and was able to punch the lifters out a bit more which was good but I also discovered the other issue making the cam hard to get out- a spun cam bearing, shell glued to the cam, knocked that off and cam drew out. It's been hot, will that have totaled the block? Any how here's the culprits, it's like they have tried to weld themselves in there! Here's a pic of each side of them.Thoughts please

 

That's a bummer, did they tap in the cam bearing incorrectly and block the oil passage?

 

The last engine failed after oil supply issues ?

 

That's correct, this one had a new hv pump and ran good pressure,we never got fast enough or ran hard enough to have any oil supply issues here, everything is oiled up nicely

 

Weird.

Lifters should alway have a good oil supply...so strange they could get like that.

Cam bearings walking.....just seems a random thing. After it happened me once a few years ago, I've mine pinned now. They wont be doing that again !

 

Hey Huffa,

Glad you were able to get those lifters out of the way and get it all tore down. How do the two lifter bores look/feel? Are they caked up like the lifters? Are they any different than the other 14? Anything look or feel off in the other 14 too? Scratched like the lifters?

The cam bearing that spun... was it the one closest to the two lifters? Did the cam or bearing have the same kind of shmoo on either?

I would have to take into strong consideration that the cam bearing is part of the chain of events. Can't see it not being. Question is, was the bearing a victim or the culprit? I could see it going either way.

If the oil galleries were not cleaned out, some bearing material may have been in there from it's previous life (or death) and smeared on the lifters and cam bearing journal causing them to bind up... sticking the lifters and spinning the bearing.

Or, the lifters stuck first, not wanting to travel to their peak lift, which overloaded and killed the bearing... while at the same time holding the valve open until the piston came up to "help" close it.

Or, perhaps the bearing spun first and it's material is what gummed everything up?

Shmoo McGoo, where did you come from?


At this point, I don't think it's worth trying to save the block. More cost effective to just replace it. And I agree with the LS9 cam recommendation. Given the torture test GM put's their engines through it would be a very good cam to run in your case. And less than $150US? Can't beat that either. You can probably even use one of the sets of springs you already have with it too.


Side observation:
I've never seen (not that I see all too many anyways) an LS7 lifter with a Chevy Bow Tie inscribed or with such poor Quality Control. Not to say the lifters did/didn't cause the issue, but are you sure they're genuine GM Parts #12499225? Just did a google picture search and didn't see a Bow Tie inscription in any of the photos.


Man, I really feel for you. This is supposed to be, and should be about the simplest method to respectable and fairly reliable horsepower. These problems just shouldn't be happening. I'm really sorry buddy.

I guess the bright side is you'll have a lot of spare parts.

 

For the record, I'm not 100% convinced the last failure was a oil supply issue. Pretty sure it was a thrust clearance issue.

 

FWIW my GM ls7 lifters did not have the bow tie emblem sign on them. Got mine on ebay form a seller specifically stating they were original GM parts and not china knockoffs. (no idea if thats true)

 

The bad lifter bores look sad, but I can't get my finger in to feel. It looks more like a build of material that may hone off? I guess that's wishful. The last engine definitely an oil supply issue, everything was dry as a chip, timing chain/rockers so on, actually starting to think thats was an overful issue causing the crank to beat the oil to a pulp aerating it, definitely nothing to do with bearing loading from jet unit, heaps of back forward free travel on driveshaft. I will look into the lifters, actually asked the builder yesterday who got them and he was positive they were the good ones.

 

Ls7 lifters don't have bow ties on them. At least mine didn't. Bought mine from gm

 

I'd be curious to know if the buildup on the lifters can be scraped off with a razor blade.

As far as the block goes, I was thinking more of the cost of machining to fix the cam bearing bore vs. the cost of a replacement short or bare block.

Pointless at this point to make the argument for the last failure. Maybe just keep it in the back of your mind that it may or may not have been an oil supply issue. If it was, you have taken steps to resolve it, if it wasn't... sounds like you've taken steps to address that as well.


The next one is going to be all smiles. Right? Third time's a charm.

 

I'll be honest, its getting challenging all these engines blowing up, this is #3 for the year and next to no hours boating. My family boat running blown 350 shat itself earlier in the year after only 13 hours on a rebuild.My mate just said to me the other day most guys would have given up jet boating with the bad luck I've had, not sure what the next best step forward is.

 

I feel your pain. It does, for sure, suck.

Food for thought

You already have all the hard parts (well, except for some lifters and maybe a cam) and all the creative thinking has been done.

A few hundred for another engine, quick tear down, file the rings, check the bearings, and slam it back together. If you had the engine now, you could easily be in the water this weekend.

After all, isn't part of the beauty of using junk yard engines that they're disposable?

 

Thanks for that. Yes you are correct the whole purpose of the 5.3 is that its disposable. I chose that direction as I don't have a fat wallet for rebuilding big blocks or buying new ct525 crate motors, just didn't bet on changing them like the rubbish bag! Anyhow, yesterday I did order a set of Johnson high lift lifters from ebay, thought they looked a good bet, made is usa, $100us,hopefully no one tells me otherwise. The chap who supplied me the engine has kindly offered to measure it up and fit new cam bearings if possible so will get it back to him and see what's the story

 

After my experiences with cam bearings I wouldnt be running any engine that didnt have them pinned. It's just far too much hassle to take a risk !

Unless perhaps you picked up a 100% standard engine...and installed that as a test bed, no turbos etc. In case there is something wrong elsewhere that is causing the problems.

Although the most recent has to be down to the build/cam timing or something, unless there was again a lack of oil supply that screwed up the lifters somehow.

 

So what's involved/cost having bearings pinned? Are bearings any more or less likely to shift in a cast block compared to an alloy block? I'm sure you are correct in saying get it done, and I can remember reading a bit about it, but there's heaps of LS powered jetboats around here and I've never heard of anyone doing that or heard of them having issues,apart from this fella. Just how common is it to have the cam bearings move?

 

IMO… All the oddball machining and BS is what causes 99% of the problems in the first place. If an OEM engine can go 300k without pinned cam bearings it isn’t necessary. The whole point is cheap easy/fun power. Grab a bone stock engine. I’d look for a 4.8 (they are always cheapest) in the best condition you can find. Run a mild OEM cam (zr1 would be my choice) If the engines been together running fine for 150K+ leave it alone. Inspect it, file the rings if needed… and run it.

 

Cost for me was very little as I did it myself.

And no idea which is more likely ( mine is alloy )......as for how common. Considering how many LS's are out there, it probably isnt that common. But it's a pain in the bloody hole when it happens to you.

It did to me...it will never happen again.