GT6 GT6 Crank Journal Measurements

[boeingpilot]

Okay, this has me stumped (not hard to do). I have stripped the engine of my '69 GT6+ down for overhaul. I was in the shop today making sure the bores, crank journals, etc. are within specs. Everything is as it should be except the main bearing journals on the crank. Both of my GT6 rebuild guides list main bearing journal diameter at 2.0005 to 2.001. My measurements are (1) 2.296 (2) 2.289 (3) 2.292 (4) 2.293.

After some head scratching I pulled my TR6 rebuild guide and found the main bearing journal limits to be 2.3110 to 2.3315.

Has this car had a TR6 crank installed somewhere in it's past? Is that even possible?

It appears that this is a TR6 crank that has had the main bearing journals ground .020 under.

Of course these things always seem to happen on Sunday when the shop is closed!

 

[TR3driver]

Definitely possible. Somewhere I've even got a period magazine article describing how to do it. Hmm, maybe it was the TriumphTune catalog instead of a magazine?

 

[davidk]

My TR-6 has a '69 GT-6 engine (according to the engine number). The last time I had the head off I measured the stroke and found out I have a TR-6 crank! If possible, measure the piston stroke distance.

 

[vagt6]

If it has a TR-6 crank, the stock GT6 oil pan probably wouldn't fit properly without some "creative" hammering in key places at the bottom of the pan.

Does your GT6 have a stock oil pan? Does the pan fit properly in the engine bay?

Not unusual to have a TR-6 crank. And if you do, you now have a 2500cc engine to boot!

let us know . . .

 

[boeingpilot]

Okay, here's the word from the shop. It's not uncommon to see GT6+ engines with TR6 cranks, rods and pistons. By substituting these parts you add 500cc to the displacement. The catch is that the block has to be machined slightly to make rook for the larger counterweights on the TR6 crank. My block does indeed show evidence of machine work. The oil pan, however shows no signs of "creative" hammering like vagt6 suggested. I'm assuming, therefore, that it must be a TR6 oil pan as well as the exterior of the blocks are identical.