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MG TD TF 1500 - Piston identification

Hi Everyone,

I am starting to examine an xpag engine which I took out of my 51 TD several years ago with a view to rebuilding it ( block no. 7239). The pistons are marked STD and measure 2.713 inches in diameter which is over .090 larger than the standard xpag size.

Can anyone identify the piston from the details given in the photo?

The piston top is marked 12387 and below that ID15 and below that Made in England.

The bores are so good that I may just replace the pistons.

Any help appreciated,

Thanks,

David


David Tinker

On my post I should have mentioned the reason for replacing the pistons is because the rings in no.4 cylinder were broken and a segment of one ring embedded in the ring groove.

David


David Tinker

There's a set of rings available on eBay UK for it: http://www.ebay.co.uk/itm/NOS-Hepolite-Piston-Rings-for-100-overbore-Hepolite-Pistons-12387-MGTC-TF-/221249193472

Looks like the pistons are far from standard...appear to be .100 over per the ad. Even Moss mentions them in their catalog, btw.
Gene Gillam

Could your pistons be standard XPEG pistons?
-David
D. Sander

David

This may or not be applicable to your broken rings on No4 piston however I communicate my experience.

The XPAG engine in my TF was purportedly fully over hauled by an engine re conditioner when I bought the vehicle. I removed the engine to fit the Moss rear seal kit and whilst the sump was off found the skirt on No4 piston broken. Removal of the piston revealed not only the piston damaged but the rings broken. It was obvious the assembler had flogged the piston into the block.

Now to cut to the chase, the block casting where No4 piston enters the bore has a small strengthening web. When inserting the piston up into the bore it is very easy to hit this web when inserting the piston resulting in ring damage.

In my case I had a very knowledgeable mechanic assist with the reassembly. He was well aware of this issue and ground away some of this web to remove the possibility of hitting it when inserting the piston. He also used a home made ring compressor to insert the No4 piston as the propriety compressor would not fit into this area of the block.

This may or may not be of assistance in your case.

Graeme
G Evans

I believe that you can insert the rod and piston without rings and let it protude up above the block. Then install rings and using a proper ring compressor push them back down in place.
Sandy
ss sanders

Yep Sandy, that's the way I've always done it. Just make sure you have the oil hole on your rods facing the correct way.

Gene
Gene Gillam

David,

Your pistons are almost certainly Wellworthy pistons, as the number 12387, is very near to the number for the racing pistons for my Sebring Sprite (regrettably, like so many of my cars, sold).

Wellworthy merged with Hepolite & Grandage and today are known simply as AE, and I'm almost sure they can supply at least rings, if not complete piston sets, on special order.

You will have to consider however, if you want the 4th ring, an oil scraper, above or below the wrist pin. You may not have any choice, as at +.090", there may not be any selection.

Gord Clark
Rockburn, Qué.
Gordon A Clark

You say your pistons are over 0.090" larger than standard XPAG, but do you mean standard bore size or standard piston size, which would be slightly smaller. You should measure the bore size, which I think will be 2.718", which is +0.100", giving 1350cc, a fairly common overbore. Initially, I would remove the broken piece from the offending piston and see if the piston can be re-used. If so, the rings on ebay, which I think are three rings per piston, and assuming you do not have chromed bores, are ideal. However, as you are in the UK, you can probably order them from any decent motor factor.
R A WILSON

Hi Everyone,

Many thanks to you all for your suggestions.

As the no.4 piston is not re-usable I have decided that the next best option is to have the block sleeved and purchase pistons to suit.

The mg spares Day is taking place on Sunday at Stoneleigh so I shall be shopping for parts.

Thanks again,

David
David Tinker

As you say the bores are good it is a shame to give up 1350cc. You could check with F W Thornton (Telford, 01952252892), who supply automotive pistons and rings. They may be able to supply one matching piston and a full set of rings. If there is a slight step at the top of the bores you will need stepped top rings (should have mentioned this before).
R A WILSON

This thread was discussed between 25/02/2014 and 02/03/2014

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