[T3] Mahle 1500 pistons

[Jim Adney]

On 6 Sep 2012 at 20:43, Keith Park wrote:

> Looking over the NOS Mahle flat tops im going to use in the crate, they say
> SP0.05 mm on them in addition to the 82.95 number.
> They are part number 311 107 105 AA
> 
> There is no indication anywhere on them that they are oversize other than
> maybe that SP number that is on the piston itself, the box is not marked
> oversize anywhere, any idea what that SP number is??

It doesn't mean anything to me, other than the fact that I've seen 
lots of VW parts boxes marked SP xxx, where xxx is some whole number. 
I've always assumed that it meant Service Part, or Service Pack, as 
they usually held a collection of parts used together to perform some 
particular job on a VW. Oddly, however, there is no mention of SP 
numbers in the microfilm, the older printed parts books, or later 
dealer parts price books that I have. My impression is that these 
sets of parts must have been an older VW system.

This was just one more thing I always meant to ask Russ about, as 
there MUST have been a reference to them somewhere. He must have been 
familiar with them.

How does this number appear? Is it inked on the pistons, part of the 
box label, or stamped into the piston crown?

If it's part of the box label, my best guess is that this is a 
Service Pack specially put together to replace the dome top pistons 
with flat tops on engines where the owners found the high compression 
to be a problem, as perhaps in parts of the world where high quality 
gasoline was not available.


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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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