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TR6 Worn #1 Exh Cam Lobe - TR6

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Bob_Carroll

Bob_Carroll

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Actually, this is a 73 TR6 engine in a TVR 2500M. Seemingly overnight, I seemed to have a "dead" cylinder. Although compression was even all around and I've verified ignition and carburation, I still have this problem. So, suspecting a "jumped" tooth on the cam timing, I pulled the cover, but no sign there. Subsequent check of valve clearances (had recently done this) indicated clearances a bit tight on all but cyl #1 - which was in spec. However, the exh valve only opens about 1/2 that of other cylinders. It's looking like a single worn lobe. Is this common? I was told when I bought this a few months ago that a prior "may have" installed a hotter cam, but I have no way of knowing if that is true or what the cam specs may be. Before I pull this puppy out, I'd appreciate hearing from anyone who's heard of this kind of single-lobe wear.
Thanks,
-Bob /ubbthreads/images/graemlins/patriot.gif
 
Bob, I have had trouble with the TR6 engine on a few occasions giving cam wear on no. 1 and 2. In each case it was a lube problem, (stopped up rocker shaft or excess wear on the rockers themselves). I hate it but you may have two problems to deal with, cam and rocker assembly, hope I'm wrong. Wayne
 
Thanks Wayne. I was starting to suspect a possible lubrication problem, but hadn't even thought to check the rocker for wear. Any chance it could just be a worn rocker and/or shaft? I guess I'll have to pull it off to check. Sure would be a lot easier than pulling the engine and replacing the cam.
-Bob /ubbthreads/images/graemlins/patriot.gif
 
Bob, I would sure check that first, you can't always tell by rocking it side to side because there is a busching on the rocker that wares into a grove in the shaft, if they are both worn it doesn't give you much lift. Wayne
 
Bob,there were a bunch of soft lifters floating around awhile back. If the PO changed the cam and used one of the bad lifters, that could cause a single lobe to go flat. It happened to me. Or, if he used the old lifters on the new cam, that could do it too. You can check for cam wear by pulling the rocker assembly, and measuring the lift at the pushrod of the suspect valve, and comparing it with the rest.
I hope it's something simple, but realistically, I think you're going to wind up pulling the cam and root causing the failure. /ubbthreads/images/graemlins/cryin.gif
Jeff
 
I just loosened the rocker on the suspect valve/lobe and it feels fine. Just looking at the movement of the pushrod it's obvious the lift just isn't there, so it's got to be a worn lobe. Unfortunately, in a TVR, there's a frame member that's going to make it impossible to remove the camshaft w/o pulling the engine. /ubbthreads/images/graemlins/hammer.gif

While I'm thinking about it, does the front support plate have to be removed before the cam can be extracted? If so, what do you use to remove timing cover oil seal adapter sleeve? I don't see how a puller could be used.

-Bob
 
Bob, I've never done a TR6 engine, but plenty of GT6's, and I believe they're the same. You don't have to pull the front plate. Just the timing cover, drop the cam gear and remove the cam keeper plate, and slide the cam out. Of course, by this time you already have the head off and the lifters removed. Make sure you check the oil pump out carefully, as all that metal from the cam failure went through it. As well as through all the bearings. I would imagine that you are going to wind up completely tearing the engine down to get to the bearings and oil passages, though.
Jeff
 
Yep. Given that I've got to pull the engine anyway, it's going to have to be completely torn down. I'm afraid I'm probably going to just button it up for now so that I can move it around (too many cars and too little space) until I can get some other projects out of the way. /ubbthreads/images/graemlins/cryin.gif

Any idea how to get that timing cover seal sleeve off?

-Bob
 
Hello Bob,
the timing cover seal is a simple lip seal and can be drifted or levered out with a seal remover.
If the crank pulley is worn, don't drift the new sleeve to the bottom, this will let it run on a fresh part of the damper.

Alec
 
Well, after two days of trying to remove the head, I finally got it off. Despite an apparent recent rebuild, the head studs rusted to the head and even with lifting the engine by the head itself, it still took about 6 hours of prying and tapping to work it off.

Anyway, I finally got the cam out and discovered four badly worn lobes. In fact, the #1 exhaust lobe was nearly non-existent.

Thanks for the help everyone.
 
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