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Triumph TR6 - Bearing sizes

Hi Guys

I am looking ahead to next winter and already know that I need work done to my head (read that how you will!) but I am wondering about changing out bearings and such "while I am at it".

As I understand it, oil pressure is a good guide to the condition of an engine, so here are the numbers for my engine -

Cold, idle - 80 psi
Warm, idle - 40 psi (drops to 25 psi after 30 minutes or more driving)
Warm, 2000 rpm - 50 psi or so

These seem pretty much okay to me, with the possible exception of the hot idle? Am I right?

If I decide to drop the sump and fit new bearings, how do I work out what size to buy? How can I measure so accurately that I can decide between standard or 10 thou oversize, for example? It seems like changing the main, big end and thrust bearings would be a wise investment (if anything TR6 related can be called wise or an investment!).

One other question about my engine fears - I seem to have some oil seeping out of No 2 spark plug hole. This is a mystery to me, since there is no real play in the valve stems for that cylinder, so the oil must be coming from below, right? It struck me that this could be a piston ring issue - does that sound likely? If so then would it be possible to change the piston rings with the head and sump off, or should I just man up and admit that the engine has to come out? I am trying to avoid pulling the engine because with my "might as well" mentality it will turn into a very expensive process!

Thanks, as always for any thoughts or advice.
Cheers
Alistair
Alistair

Those numbers don't really sound that bad, not stellar, but there are much worse out there.

The bearings should be imprinted with information indicating if they are standard, .010" undersize, .020" undersize, etc. Look for scoring of the crack and the bearings, is there any evidence that the bearing has worn to very near the backing material, etc. You can check bearing clearances using Plasti-gage, just follow the package directions. Swapping out bearings and thrust washers is a worthwhile thing if you have low oil pressure or you're just flat nervous about things and can be done with relative ease in situ.

Oil control ring issues are not unheard of even with good compression. Yes, you can knock the pistons out and swap out rings without engine removal. Same things apply about checking for scoring, etc. If you go there, you may as well get a good measure on the bores since you have the head off and pistons out. Which in turn gets us to the next paragraph.

Bear in mind that you could very well be setting yourself up to yank the engine anyway. If the measurements you take on the bores show excessive out of round conditions, clearances, or the bearing clearances are too much for a readily avialable bearing but not large enough for the next undersize, etc the engine need to come out. You can't really bore the cylinders with the engine in the car nor can you grind the crank.

I am afraid that most of us on the board are well aquainted with the "might as well" or the "whil I'm at it" syndromes. As far as I know there is not much out there to address those afflictions.
SteveP

Steve
You are being kind. I know you know the best solution is pull it and do it right. It really is not that hard to pull a TR6 engine and tranny.
Alistair.....2 things
Scott Helm...thrust washers
and BPNW.... VP2 King Brand Bearings
Rick
Rick Crawford

Yup..

I had the syndromes Steve talks about. I was going to do it from the bottom but when I got in there I found that I could just put new bearings in but 'It would be best' to get the crank reground. I could have gotten away without the crank grind but there were some slight ridges on a journal so 'I might as well do it right'. I ended up pulling the engine and doing the works with .030 pistons and heavy duty crank and rod bearings. The same crank and rod bearings from BPNW that Rick Mentions. Great bearings.

Don't be surprised though if your hot idle PSI isn't much better than 25lbs even after a rebuild. I think it has a lot to do with the generous bearing to journal clearance that Triumph allows. That's probably one reason the manual specifies 20W50. If you go on the tight side of their clearance you might get that hot idle oil pressure up. When that 20W50 oil is hot it's pretty thin. If I recall the Triumph clearance spec. is .001 to .003. Mine was on the high side of that clearance.

The whole rebuild process was easier than I thought. It also helped that I found a great machine shop that talked me through much of it. And of course they did my machining. Do some research of good engine machine shops in your area. It makes a big difference.

Good luck.

Henry
HP Henry Patterson

This thread was discussed between 20/06/2007 and 21/06/2007

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