cam bearing destruction?

M

metalgearscout

New member
Just swapped in good used trans. Took for voyage and all was good other than running on the hot side (220f). Was idling to warm up to add water after replacing tstat and it made a sound like a diesel and ran rough. Diesel sound continued and I hoped for something broken in the valve train. Rocker, rocker shaft, something happy like that. Pulled covers and all seems good, tight, clean. Ran it with covers off. Did pump some oil, but noise was intense. Well I have great oil pressure still, never dropped. Changed to 20w50 and was just gonna run it to the bitter end. Started it up, warmed up and ran bad hot. Vac gauge was reading way low and the needle jumped like crazy. Sound like cam bearings? The clatter is amazingly loud! Tia (I did check torque converter bolts right away, they are tight)
 
I don't think you would be able to "hear" cam bearing failure in an engine, simply because failure of the bearings wouldn't affect how the cam itself interfaces with the valves in a major way. The bearings just end up letting go of their mounted positions within the bores and spin with the cam - destroying the bore. Though I guess if the bearings disappeared -entirely-, there'd be a lot of "slack" in the cam.

What you are describing sounds like something else entirely - perhaps your lifters are "collapsing" as I've heard they are prone to do in a used motor, or something else like an irregular (damaged) cam lobe or few. Either would create quite a bit of tapping racket.

Hopefully you can get it figured out before it becomes a big issue.
 
Scout engine noise video by tbone - myspace video

Link to video of noisey engine
I've read and reread the thread on the lube system and just doesn't seem to apply. I've always used mobil1 and changed it regular. It did sit for a few years before I got it and was pretty carboned up, but after running it for some years with the 195 tstat and constant oil changes it really cleaned up. Seafoamed it back in the late 90s too. Not sure how much oil should be coming up thru, but gonna pull the covers and clean everything off to check that. If lifters went south what are the odds they would fail instantly like that and make that much racket?
 
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Unfortunately it does sound like a cam bearing problem. May have spun or eaten the rear bearing that supplies oil to the lifter galleries. No oil equates to all lifters collapsing at the same time.

Drain the oil and see what comes out. Next cut the oil filter open and look for metal around the outside of the element.

If it ran that well before starting to tick, I would pull and freshen up the engine and run it for 20 more years.
 
Thank you for the responses. It does make sense, the rear bearing and no oil up top. When I ran it with the covers off it flowed some oil onto the exhaust manifolds, but not what I expected at all. This was a strong engine, but I have no garage and not much time. Might become an engine swap at this point.
 
There is one sure way to determine the issue. Diagnose!

The process is posted, do the work!

There is not a day goes by I don't get an email from someone regarding this same exact situation. And the end result is always the same, the cam bearing(s) have taken a shit. A stuck valve(s), broken valve spring(s), noisy/collapsed lifter(s), broken rocker arm(s), flat cam lobe(s), bent/broken pushrod(s), etc. Are all caused by lack of lubrication to the valve train/rocker assembly or lifter oil gallery.

http://www.forums.IHPartsAmerica.co...I-4-sv-engine-non-oiling-rocker-assembly.html

And:

http://www.forums.IHPartsAmerica.co...IH-lifter-rattle-syndrome-what-do-I-have.html
 
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