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MG TD TF 1500 - Replacing piston rings

I pulled the pistons yesterday to replace the rings as the black smoke was becoming an environmental hazard. No. 3 cylinder was low on compression and the plug was oily. Piston removal from below was not a great issue but no. 1 piston was extremely difficult to get out. Heres a photo of the culprit-no. 3.
The ring is badly scored but the bore seems fine and the ring gap measured up at 0.4mm. The WSM states 0.15 to 0.25mm.
The questions:
Is there a trick to refitting the pistons from below? What method is best to compress the rings? The bottom of the bore is not chamfered. The ring compressor that I have is wider than the piston and catches on the crank. I did shorten it but daylight failed and will have to try again. Is it possible to insert the pistons without the rings from below and push through and then fit the rings from above and push back? Am I missing out on something?
I have ordered new pistons and rings.

Regards
Declan



Declan Burns

Hi Declan,
Once the Head is off the pistons normally come out through the top and go back the same way.



Regards

George
G Mills

Hi Declan. I believe it is possible to do what you propose. Fit the pistons from below, poke them out of the top of the block , fit the rings with your compressor & then lower them into the block. Still waiting on the remanufactured decals. Cheers
Peter TD 5801
P Hehir

XPAG con rods do not come out through the bores.
Wrap some shim brass around the rings and compress them then tie with some thin twine. This will give you enough room to fiddle the piston past the crank.
Don't forget to hold the piston by the gudgeon pin while loosening/tightening or you WILL twist the con rod.
By pushing the pistons up the bore you may fit the top rings but not the lower oil rings.
Ray TF 2884
Ray Lee

I knew there would be something different with the MG, but it does not surprise me, I have not come by that before and I have pulled a lot of engines down, live and learn as they say.


Regards

George
G Mills

Thanks all for the info.
Google found this thread on another Website.
http://www.mg-cars.net/mgtd-mgtf1500-bbs/rings-201311170018339954.htm
Ray thanks for the advice -do you mean when tightening the conrod bearing caps?

Regards
Declan
Declan Burns

Hi Declan,
not the caps but the Gudgeon (wrist) pin clamp bolt.
The "H" section con rod is quite flimsy and I have come across a few that were twisted.
See WSM fig A13 in section A
A couple of cut down bolts will do the job.
Ray
Ray Lee

Thanks Ray,
I'll look into that if I have to replace the Pistons-I might just get away with new rings.
Regards
Declan
Declan Burns

Declan,
The link you referenced above was started by me.
I have just recently gone through this whole procedure with the engine in the car.
Check the cylinders. I used a ridge reamer and also honed the cylinders.
Do you have or can you borrow an instrument to check the bore on the cylinders. Check in several locations both high and low.
The pistons come out through the bottom. Put them back through the bottom without the rings. Push the pistons up through the top of the engine and put the rings on. There are many types of ring compressors available. Tapping the piston down through the compressor with the wooden end of a hammer or other soft material is pretty simple.
The whole procedure went well and the car is running great.
Mort



Mort 50 TD

Thanks Mort,
The car is at my mate's place as I only have a small garage and no lift. He has a bore gauge and will take the measurements. We would have done it yesterday but time was not on our side.
I don't expect problems with the bore as you can still see the hone marks and the pistons appears quite new to me. The second ring on No. 3 is scored and the top ring show signs of pitting.

Regards
Declan
Declan Burns

Mort,
What brand rings did you use and what did you set the gap to?

Regards
Declan
Declan Burns

Declan,
CR Tyrell



If you expect to run the pistons and rings up from below, you'll likely have to polish a smooth chamfer at the bottom of the bore to ease the rings up. Not impossible. Everyone else would poke the pistons up above the block deck, without rings, install the rings, then drfit them down.

What bore is that for? You probably don't need to replace the pistons. If the other pistons look as nice as #3, then send the old batch to me!
JRN JIM

Declan,
I got the pistons and rings from Moss.
Mort
Mort 50 TD

Thanks Mort.
Regards
Declan
D Burns

This thread was discussed between 18/05/2014 and 26/05/2014

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