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MG MG Y Type - Piston height / decked block; what to do?

I think I'm in trouble with my pistons that stand proud of the engine block that was probably decked more than one's.

The old head gasket is about as thick, leaving almost no clearance, I don't think that's enough? See the pictures.

What is the best solution, apart from getting the pistons out again and having them turned down?


Willem van der Veer

and another picture

Willem van der Veer

Two head gaskets.
R A WILSON

The pistons should not be coming up that high at all. Are you sure you have the right con rods in Willem?

Paul
Paul Barrow

Paul,

I didn't change the rods, the block was decked by the machine shop. I guess they overdid it.
Willem van der Veer

Hi Willem.
I had a similar problem with an XPEG block and had to machine 1 mm off the piston crowns. Worked a treat, the pistons were new but the crowns were too high.

Unfortunately you will need to strip your engine to correct your problem.
Regards Wayne
W Routley

Oh I see - when you say decked you mean what we would call 'skimmed' in the US. I didnt understand what you meant the first time and yes they over did it!! They should have known how much they could take off before they started just from regular data books (the ones my engineer uses include XPAG engines!) and before he machines anything he checks all 6 reference books. I hate to suggest it Willem, but your people do not sound that good and I would hesitate before taking them any more stuff, especially the piston crowns.

Paul
Paul Barrow

Paul,

I thought you skimmed the head and decked the block, but that's what you get when English is not the mother tongue?

The thing is, when I entered the reputable machine shop that was recommended by several (non MG) people, I was asked what kind of engine I had. I answered 'an MG engine.
OK, said the man behind the counter, 'that's one for Bert'. Bert turned out to be a rather young guy who took one look at the engine and exclaimed; 'ah, an XPAG'. One minute later he rightly deduced that it was a later block with 8" flywheel and an early, quite thick, head.

It turned out he was working on three other XPAG's, and his late father was a leading MG enthusiast with several top (real) concours restorations under his belt. So I have no reason to believe that he didn't know what he was doing. Maybe as Wayne suggested the pistons are too high?

I will try two head gaskets first as I am in a desperate hurry to finish the engine before driving to Germany for the Y-Sommertreffen. After that I will source or make a solid copper gasket of 2,5 mm or 0.1 inch thick.
Willem van der Veer

You may be right on the terms there Willem - I am no engineer or machinist ... I leave that to my engineer and machinist guys who are :-).

Never to old to learn new stuff - http://www.google.com/search?q=decking+the+block&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=

Paul
Paul Barrow

Willem,
For someone whose "mother tongue" is not English you do better than many Englishmen.

I looked up Decking on the web.It does mean machining the block, although I think it may be American usage, so if you think Americans speak English, which sometimes I doubt, you are entirely correct.

Best
Michael
Michael Nicholson

That is an affirmative Michael!

:)

Paul
Paul Barrow

This thread was discussed between 09/06/2013 and 13/06/2013

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