ABA pistons in a 3A? Will they fit?

[jdbubb at verizon.net (Dan Bubb)]

Wrist pin height (nominal, pin axis to top of piston) is 30.6 mm for an ABA piston.
3A pin height is 29.6mm or a crummy 1mm/.040" difference.
There is an additional complication in the fact that the ABA uses a 21mm diameter wrist pin where most other VW watercooled including the 3A use a 20mm wrist pin.
So, first glance says you'd need a 144mm stock rod reconditioned with a 21mm small end bushing offset 1mm.
Don't know if the stock rod is up to that although I could take a look tonight and see if it's even feasible.

>From my experience building my nephew's turbo engine with JE pistons, it seems to me that the JE's had a much bigger head to piston clearance than the .040 min clearance recommended although I never measured it. It was just noticeably bigger clearance than my Wiseco pistons that I did measure and they were spot on. Maybe just rebushing a rod for a 21 mm wrist pin at stock length would work. Perhaps just milling a little off the top of the piston crown (which would just be the perimeter anyway) would be the ticket. Want to be careful to not take off too much since IIRC these are low compression pistons meant for a forced induction application and it's a good idea to have a nice thick top ring land in this case.
In any case if one wanted to use them in a 3A they would need to be a position to take the appropriate measurements and potentially make several trips to the machine shop to get all the parts to play together.

TMI??
Dan


From: "Mark F." <mardak@gmail.com>
Sent: Wednesday, March 15, 2006 1:41 PM

> I have a set of new JE pistons for sale (83.5mm bore ABA), and someone
> who wants to put them in a 3A is interested in them.  My guess is that
> unless a different connecting rod is used it won't work, as the piston
> pin to piston top measurement is most likely different between the 3A
> and ABA blocks.  If this is the case, what size connecting rod will
> work (and what stock VW application has such a rod)?
> 
> Thanks!
> 
> Mark.
> 75
> 82
> 86