Moss Motors, Ltd

I bought a TR6 "kit" and afterwards I found the engine is a GT6.  I have a spare 74 TR6 engine I am about to start rebuilding but the engine in car was running bad so I decided to do an incar rebuild just to make it through the summer.  #5 cylinder was very low.  I pulled the pistons out and found a large part of the piston ring grooves missing.  I really need just one piston.  There is a number inside the skirt AE 17753.  It is 020 over size and it's obvious the engine has been rebuilt so I'm thinking it was done with TR6 pistons.  Both the TR and GT have the same bore size.  The difference is in the stroke.  Would that be in the crank/rod length difference or would that have to be in the piston too?  Crud, I wonder if they put a TR6 crank in there?   Anyway, the bottom line is I'd pay about $300 for a cheap set of pistons & rings for a TR6 rather than a $450 for a set of GT6 pistons.  Remember, I going to only run it for six months and that money really needs to go to the TR6 engine rebuild.

The stroke is only controlled by the crankshaft throw, that is, the distance from the center of the main bearing axis to the center of the rod bearing axis. Different rod lengths and piston crown heights are then used to determine the location of the top of the piston when it's at top dead center.

You need to determine what your crankshaft throw actually is. Then you'll know what parts have been cobbled up to make this engine. Are you sure you want to spend this money for a sorta-rebuild? Personally, I think I'd delay gratification and get going on the "real" engine, but that's just my perspective. I'm sure you have your reasons.

Why not pull the actual TR6 engine apart and compare pieces? Then you'd know for sure what you're dealing with. Repost if this doesn't help

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

I know the stroke idea, and the rod length can be changed to locate the piston, but does it mean that the piston is acutally diffent?  Remember the Midget engine was completely renumbered even though it was a Spitfire engine so who knows from the part numbers.  The reason I'm not jumping into the "real" engine is I use my TR as a near daily driver and I don't have the money now to do a proper rebuild of the TR engine right now.  The idea was to mayby spend $200 on rings, bearings gaskets and maybe a piston and then I could take my time and rebuild the engine right without feeling rushed and putting myself into depbt and I'd rather not have the engine laying about in pieces until I do.  I have many uses for my garage and don't have the space.  I didn't count on the everyone sells only full sets of 6 pistons part.   Anyway, I've decided to use a TR6 piston since that's whats in it now (part# AE 17753) and found a place in Canada that will sell only one at a time at about $60.