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fester

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Gympie, Qld Australia

1st Oct, 2005 at 01:18:48pm

Guys until I can find my measuring sticks can you help me with the pistons in this engine I bought.

They are turbo pistons (20831) but what marking denotes standard or overbores. The only other marks are an "A" in the middle of the piston top and also cast into the underside and along the top outside edge next to the part number is what looks like 1D7 or 107 ie 20831 1D7

I"m assuming they are oversize only because I supect the motor to be rebuilt otherwise someone was very religious with oil changes as the block and head are as clean as a whistle, no burnt or old oil stains at all. Also the engine number plate is gone and the number is stamped on which means at least the block has been skimmed.

Gavin


Dangerous

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Swindon

1st Oct, 2005 at 04:46:20pm

the A is just the grade,you gt A and B engines new


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Doodmeister

485 Posts
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Alberta, Canada

1st Oct, 2005 at 07:40:34pm

At a guess +0.20 on the piston crown would denote oversize pistons.

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turbodave16v
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SouthPark, Colorado

3rd Oct, 2005 at 02:38:20pm

Oversize Pistons are Very obvious from the markings as Doody commented. If it don't say it, they're stock.

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Amp

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Essex

28th Mar, 2015 at 08:16:20pm

On 1st Oct, 2005 Dangerous said:
the A is just the grade,you gt A and B engines new


Bit of a thread excavation but it was the only thread I could find that referenced it!

My question; does anyone know what the "A" or "B" stamped into the crown on the 20831 pistons represents exactly?


Carlzilla

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Quarry Bonk

29th Mar, 2015 at 10:11:16am

I think, it's the accuracy of the machined piston, and they would use either A or B depending upon the accuracy of the machined block, so they mix and match for best fit. But don't quote me on that.

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