Piston Woes

[Spider]

On removing my pistons from an engine that has been seized  from being stood too long, I had to use a 4lb club hammer to unstick one of the pistons, with a wood drift between the two, however the piston shot down the bore so quickly it damaged the skirt on the main bearing housing. Is it possible to purchase just one piston as the others are in good nick with no signs of any wear, low mileage engine, if so where's the best place to look.
The rings are stuck in the other pistons, I was thinking of using phosphoric acid but was not sure if it would damage the pistons. Has anyone else used this method or are the other methods that you guys use.?

Many thanks
Spider.

[Jonny-Jimbo]

When I did the engine work at Ginetta we just used diesel to unseize stuff, usually worked well.

[Nick Moore]

I think phosphoric acid will give you undersize pistons fairly quickly. Mind you, once the pistons have dissolved enough, the rings should slip right off.

I think the easiest solution is a new set of pistons, unfortunately.

[Gt6s]

Do not use any form of strong acid or alkaline.

You should be able to buy a single piston okay.

Just break the rings out then use the broken end of a ring to clean up the grooves.

Laurence

[junkuser]

You could try boiling the pistons in water to free the rings.
Different coefficient of expansion of the steel and alloy may well free them and it will not risk any damage, so worth a try as first step.

[JohnD]

I don't think that phosphoric acid will erode aluminium, as like iron phosphate, aluminium phosphate is almost insoluble in water, so will leave a hard coating of AlPO4 on the piston, that is sometimes used as as a base coat for piant and other coatings for aluminium.    But it's not good news as the layer of AlPO4 will further lock the rings into the grooves, so take the advice above.

John

[Spider]

Thanks for the advice guys. I have managed to remove one ring and break one so a set of new rings will be on order. As to the other querie about buying a single piston does anyone know where I can purchase one and what is the difference between 2000 and 2.5 flat top pistons? The bores I believe are the same so is it to do with the gudgeon pin position?

Many thanks
Spider.

[Nick Moore]

Yes, the gudgeon pin is higher in the 2.5 pistons, as the crank has a longer throw. Of course, if you end up with a set of 2.5 pistons, all you need to get 2.5 litres is a 2.5's crankshaft. That's what I'm doing with my GT6 motor.

Oh that's right, I almost forgot. If your GT6 had domed pistons you can use the head on a stroked version. But if your 2L pistons were flat, you can't. My bad.

[Spider]

I think the 2000 motor will have to wait for a proper rebuild as I have 2 x 2.5 motors, one to go into the GT6 and one to go into the MK1 2000. Once I pull the 2000 motor from the MK1 I may use a piston from that to rebuild it's original engine, both early MK1 motors with the small bearing cranks.
  All I want now is  a couple of TR5 camshafts. Oh and some decent weather so I can work on the cars.  :-/

P.S and a Mike the Pipe manifold.  :)

[JohnD]

Spider,
Quote, "I have managed to remove one ring and break one so a set of new rings will be on order."
NEVER rebuild an engine without new rings,  and honing the bores too.
To do otherwise would be like putting the old oil back in!

I have several partial sets of of pistons, domed, flat and 2 or 2.5.
But your last post sounds as if that project is off the stove.
PM me when you want one.

John

[dinger]

Be careful .. piston sets are supposed to be selected such that they should weigh the same and there can be minor design differences . A replacement if not the same weight, may cause vibration not there before due to out of balance forces .. If you intent on buying oddd piston , be prepared to at least check its weight with one existing ..