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Triumph TR6 - Confusing Engine

Picked up a spare engine for my 71 TR6 yesterday. To say the least it has me a little confused....

The engine was pulled some time ago from a 74 TR6. It has the late head, late intake manifold and the dual pipe exhaust manifold. So everything seemed to check out.

Didn't notice till I got it home it has a 'KF' prefix. That should make it a (1973?) GT6 2.0L engine - not exactly what I was looking for. Decided at that point to tear into it to see what parts were useable for my needs.

Pulled the head and found stock 2.940" bores still with cross hatching and no ridge. It does have the cylinder counterbores for the later head gasket. Then rotated the engine and found it has a 3.740" stroke. So I guess it's not a 2.0L after all, but a 2.5 instead? Pulled a couple of main caps and the crank has been ground/polished .010 under. BUT, it's the 'long back' crank with the pilot bush in the crank, not in the flywheel. It looks like I have a 'Frankenmotor'!

The BAD news is both of the thrust washers had dropped out and the crank is a mess along with the main bearing cap. Haven't been able to check the block yet to see how bad it is.

Looks like this will have to visit the machine shop to get cleaned up and custom thrust washers made. Has anyone else had to do this? And to think I just wanted a decent runner to drop in while I rebuilt mine!

I'd appreciate any comments or suggestions you guys have.

Tom Sotomayor

Tom- Not uncommon

Frankenmotor indeed by the sound of that lot!

Possibly a "one off" build by an "enthusiast" hoping to get the best fo all world within the Triumph sphere?

I do know of something similar done to a GT6 when the original engine finally expired (through years of total neglect I might add) and the then new Triumph 2.5 PI engine was fitted as a replacement.

The "builder" was less than competent and promptly managed to plumb the high pressure fuel pump to fill the spare wheel compartment from the fuel tank !

Interestingly the cross hatching is still visible and no bore ridge so it seems to have done little service perhaps?
The undersized crank means an earlier refurbishment but no problem if all is straight and true.

Your suggestion of having a decent machine shop take a good look is the way I would go as well.

There may be a way out of the maze after all.
Hope so anyway.

Keep us updated as to how you progress.

Cheers , Pete.
Peter Thomas

Thanks for the input guys. Haven't dug any further into it yet, may get to it next week when I'm off for the holidays.

Well, it's already in my 'machine shop' - don't know if it's decent though! Touching up the crank in my lathe won't be a problem. Not sure if the block will fit in my Bridgeport mill or not. Had that torn apart over the last 2 weeks fitting a longer table and haven't had a chance to measure if the table can be dropped enough.

Reading Roger Williams' books he talked about making custom thrust washers out of phosphor bronze. Big $ there just for material! May opt to make a split carrier for standard thrust washers. I'm planning on doubling up the washers and making the carriers attach to both the block and cap.

I'll keep you posted on progess.

Tom Sotomayor

Here are the thrust washers you want...and made to your requested size to boot! $20.00 eash.

Scott Helms BETTER thrust washers.
Rick Crawford

Add an oil port to the last thrust washer

Rick - Thanks for the link to Scott's site. I read through his saga and it's not surprising he had trouble with the stock thrust washers after he damaged his crankshaft. With the uneven wear on his crankshaft it greatly reduced the surface area contact on the new bearing. Add to that it wasn't able to build up a hydrodynamic oil film and you'll get the rapid wear he experienced.

Don may have hit on the key to it all. I may just try that, but probably not the way he envisioned!

Having a lot of experience with MGs it's not uncommon for those thrust washers to last 150k + and still look like brand new. Sometimes you'll see a little scuffing, but not enough to warrant replacement. The only real difference I can see is those cover 360* while the one in the TR only covers 180*. This goes back to my earlier comment about a hydrodynamic oil film. It's tough to maintain one if the bearing surface is not continuous. No oil = rapid wear.

To work it back to Don's suggestion - If the thrust washer is on one side of a main bearing, the oil ejected from that side will fill any cavity between it and the encircling thrust washer. In effect you get (at least some) pressure oiling. In any event you'll get a steady supply of oil rather than relying on the oil fog / splash found in the crankcase.

Anyway, that's my theory!
I've also found a more reasonable ($) source for bronze so will probably make my own. Hey, playing on the machine tools is almost as much fun as playing with LBCs!

Just wondering about something. The MGs have a graphite clutch throw out bearing that wears VERY quickly if people hold in the clutch while waiting at a stoplight. I wonder if it could be the same issue with the TR thrust washer....

Tom Sotomayor

This thread was discussed between 12/11/2006 and 15/11/2006

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