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MG TD TF 1500 - XPEG Block Height

My XPEG engine has been decked, but i do not know how much, I will measure what I have, but does anyone have the original specification for the block height (centerline of crank to top of block)for comparison? It would help confirm the compression height of the pistons I will be ordering...I could not find that dimension in any of my manuals. My old pistons when fitted sit .020 above the top of the block, but the machine shop is saying they just shaved a few thousands to clean it up...

thanks
Joe B
Joe Buchmiller

Wow! My pistons are sitting about +.007. I was concerned until I found that the gasket was .042-.045 when compressed. The resultant squish area approaches an optimal value. Yours may be problematic. A solid copper gasket may be the simple solution as they are available in several thicknesses.

Perhaps this is not the first time the block has been decked in the past 60 years.
JE Carroll

Joe,
The XPEG block I am working on has less than 6,000 miles on it and has never been "decked". The dimension from the pan flange to the top of the block is 10 13/16" as best as I can measure, due to it being partially assembled.I used a large carpenters square on the pan flange and a 2 ft level on the top of the block. It should be pretty close. Hope this is some help to you.

George
George Raham [TD4224]

I believe the correct dimension is from the crankshaft centre-line to the deck.

I did have that number at one time, but can't now find it. Sorry.

Gord Clark
Rockburn, Qué.
Gordon A Clark

If you need a larger(thicker) copper head gasket, Hussey Copper in PA can make one for you. They can do any thickness you need.
Tom Maine (TD8105)

thanks guys - I am ordering custom pistons and I will be setting the compression height on the new pistons to the deck height needed for the compression ratio I want, I was just curious as to what the original specification for the block height was so that I can verify where I am at... I have not been able to find that, I can do some reverse math on the assumption that my previous replacement pistons were stock compression height and would have been at "0" deck height in an original block, but that is an assumption that the the last set of pistons were made to stock specifications, and that the factory set the pistons at "0" deck height.
Does anyone have the original specification for piston compression height and their installed deck height? George - thanks for measuring your block - but it looks like I need to get a more precise dimension to do me any good.

Joe B
Joe Buchmiller

Have a couple of bare blocks here, Joe. Measuring from the oil pan mount flange to the deck is 10.685 on one block and .010 more on the other. More accurate measement from top of front main bearing saddle to deck is 9.440 and 9.430 on the 2 blocks. Shorter block has probably been decked in its life. Do not have a factory spec available - what does yours measure? Dan
Dan Craig

Thanks Dan
Mine measured 10.660 at the bottom of the block, and then
10.538 at the actual centerline of the crank. 9.415 from top of saddle to top of block.

So your dimensions are pretty close to what I expected, and my block has been decked somewhere between .015 and .025
Joe Buchmiller

This thread was discussed between 29/10/2011 and 31/10/2011

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