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MG TD TF 1500 - Pistons 3 ring vs 4 ring

Tried to search. Came up with nothing.

I noticed a set of four ring pistons for the TD and then looked at Moss and they have three rings ones. The price difference is huge. $1000 vs $125. Trying to save some money on a rebuild of a spare engine.

Can I use these? Pro and cons?

Thanks

Joe
JWP Policastro


As far as I know, the factory only used three ring pistons. I use the four ring pistons offered later. I feel that the fourth ring helps stabilize the piston against "piston slap" as well as possibly providing more oil control.
Joe, this ought to start a lively discussion.
Jim Merz

Oh boy. I did not know I was walking in one of those MG TD mine fields. Sorry Jim.

Joe
JWP Policastro

Just built my street TF 1500 engine with 4-ring variety from Abingdon about 1 1/2 years ago. Didn't think anything of it at the time. Seems to me some MGA's and B's had 4-ring pistons?
I'm curious if anyone has real comparative experience with the 3 vs the 4 ring. I can't see how the extra ring is too significant, except to help to control oil consumption, on a non -competition application.
T W Moore

I have four ring pistons and very low oil consumption.

However, I do think the bottom ring causes a lot of extra friction. I have read that often the bottom oil ring is not fitted to overcome that 'problem'.

Be careful though with the piston pin to crown measurement. I suspect my pistons are too high which forced me to fit a thicker solid copper head gasket.
Ask the seller to give guaranteed measurements of the piston that you can compare with your own before buying.
Willem van der Veer

Thanks for the input. I will be putting in new liners and boring them to fit the piston. This should cost about $500. In the past, I remember that my MGA engine had four rings. Worked OK.

Willem that is great advice but unfortunately I have no existing ones and I am just putting pieces together to build it into a motor. My thinking is that at $150 for four new Pistons and rings it is probably worth the gamble. I am a couple of 1000 miles away from the actual pistons. Moss wants $1200 or so for new ones.

Thanks again for the input you guys really are a wealth of knowledge.

This is kind of a low budget rebuild. To give you some idea I bought the block, crank and cam for $400. Bought a used head for $200 that had been ported and polished. Bought new bronze guides ($70) off EBay and oversize valves from The Frame and Up.

Had the crank done to .010 over ($125), had the cam reground to a RV grind/fast road and the tappets resurfaced ($124), had rocker assembly totally rebuilt ($200), machine work on the head was $400 to put in new oversize valves and guides. I had block dipped, etc, and put in new brass freeze plugs ($125), push rods, crank, and head magna fluxed OK. Found some Vanderfall(sp) bearings ($90). Still need to pick up some other bearings and some odds and ends like a gasket set, etc.

Not sure I could do it cheaper considering I had to buy all the parts.

Thanks again for the input. It is always nice to get another opinion and experiences.

Joe

PS Forgot I do need to buy a oil pump rebuild kit.
JWP Policastro

Where are you finding $1000 piston sets? The most expensive Moss lists are $328 sets for TF-1500s. I recall some years back discussing with a machinist leaving the bottom (4th) ring off of four ringers for less friction. I think he thought something about the very long stroke and length of the XPAG pistons that the bottom ring would hold the piston more stable in the bore? George
George Butz

George thank you. I misread their catalog. I read over set. Thanks.

Joe
JWP Policastro

This thread was discussed between 28/03/2016 and 30/03/2016

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