Piston identification

[DJones]

I pulled a couple of old engines apart today, whilest both have the standard size markings on one side i.e. 80.98 one engine set had -05.11 marked on the oposite side and the other engine set had +05.12.

Does anyone know what these later numbers identify? As my understaning was they either had 80.98 - standard. 81.23 - 1st oversize. 81.48 2nd oversize.

Both sets were Kolbenschmidt pistons.

Thanks in advance.

Darren.

[newsh]

I'm pretty sure they're graded for final size.

[djh]

aby and 3b differences?

[DJones]

aby and 3b differences?

Yes one was an ABY and the other was indeed a 3b but what's the difference? they measure identically with no other obvious identifying factors... I thought they were all same in the turbo engines.

Thanks - Darren.

[DJones]

I'm wondering if it is to do with balancing/weight of the piston, as they are all the same part number. RR, ADU, AAN ABY & 3B....

[DJones]

I have just weighed them and the + ones are heavier so I'm guessing that's it..

[JariP]

How big is the weight difference?

[DJones]

How big is the weight difference?

Circa 4 grams each.

[djh]

do you know which was the lighter set the aby or 3b?

[Billman]

I believe they put in every engine either all + or all -. so the deviation between pistons in one engine is as small as possible (in mass production)

[DJones]

do you know which was the lighter set the aby or 3b?

The 3b were lighter. From what i have found out they have a target weight when manufacturing and the + or - is a reflection on how far away from that target weight they are..

[aelred]

All sorted then Mr Jones

[DJones]

Yes Mr Smith you live and learn....