Sunday, January 2, 2011

AA Pistons


These actually turned out to look pretty good, and going through some old magazines, it turns out AA have been producing VW pistons for about a decade.

They weigh about 10-20g under a stock piston (but are 90.5 "B",) have the graphite on the skirt, which is a "short skirt" - this is supposed to produce less friction and result in a lighter piston.  I'd like to end up with a little "fuel economy" on this engine if I can.  Pin fit is excellent and the ring set looks good for my application - street use, with ability to blast up to 6000 rpm or so (if I can afford it at the time, I will have it balanced to 8000, but my cam and heads won't produce too much at that level.)

Ok, they are "cast" rather than "forged" pistons, but outside of crazy levels of supercharging, that is what most of the world is using these days...  They also come with proper circlips rather than the wire things VW supplied.  If anyone out there doesn't know, always fit these with the "wider edge" out - look at the ring from the side, you will see a slight chamfer from where they were pressed, so the bottom of the pressing is slightly wider than the top. If you fit it with this side out and the groove in the piston is good, it should be impossible for it to come out unless the piston is destroyed - any lateral pressure on the gudgeon pin is pushing the clip further into the piston.

The cylinders themselves are beautiful - measure and look better than the VW originals I bought from Gene Berg a few years ago...  ...OK they measure as good, but they don't have the casting flash of the South American "genuine VW" cylinders.  They also appear grey, rather than black, but as they are cooled by fan forced air, not radiation, this should not affect performance.

I have the total seal seating compound which I intend to use - does anyone know if this contains abrasives?

I will post some pictures of the pistons up here shortly if it turns out anyone is reading this blog.

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