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I'm building my Aerovee engine. I found one piston ring out of spec, end gap .025". Reading the paper that came with the cylinders, it says all parts must be washed and oiled. No mention of this in the Aerovee manual. Long weekend....no tech support...:-(

For washing, I filled up our laundry tub and immersed parts then dried and sprayed a light oil on everything. This was the last operation after throughly cleaning the parts looking for bits of machined metal.
Also spent hours enlarging the areas around the cooling fins where the casting had not sufficiently done a good job. I opened up several areas so the cooling air could easily pass through the fins on the heads. I'll see if I can find a picture to post. Ok, just took a picture...some of the passageways were totally nonexistent. Just a thin membrane of metal remained which I opened up as much as possible. I'm referring to the area between the cylinders.

If it makes you feel any better as you are opening up those holes, the heads that came for my Lycoming needed even more work to clean them up. ;-)

If I understand correct you are asking about the washing instructions that came with the piston and cylinder set. In my experience building and rebuilding engines, anytime you hone a cylinder, new or used you leave a good amount of grinding material from the hone in the cylinder. In this case the cylinder manufacturer is telling you that the abrasive material is left in the cylinder (very fine stone in every cross-hatched scratch) and wants you to remove it before you assemble and run the engine. The idea behind this is to leave the cross hatch scratches in place to hold oil to lubricate the rings as the engine runs without giving a direct path for blow-by gasses to get from on top of your piston to the bottom. If you don't wash out the abrasive material, as soon as you start the engine, you have grinding compound in your cylinder that is moving in the same direction as the pistons. This makes new scratches across the cross hatches and allows for a larger amount of blow-by just like an old worn out engine. The effect is not huge, but it does exist. My suggestion and what I have practiced on many engine builds, is using dish soap and water with a non scratching nylon brush to aggressively scrub the inside of each cylinder. You'll be amazed by how much abrasive comes out. Soap seams to grab abrasive stone better than parts cleaner. Immediately dry and oil to prevent corrosion. It is true that the engine will run without doing this, as I'm guessing most Aerovees are assembled without washing, but clean parts give your engine the best chance at highest power and greatest efficiency over the longest life. Don't get me started on oil filters...

Good luck with the build.

I for one always like learning new things. Please proceed with your oil filter knowledge!

Thanks for the replies guys. I have rebuilt about a dozen engines, but never a new VW. Mostly Rotax 2strokes, and have always washed abrasives out of cylinders after honing. I'm am very surprised that there was nothing in the manual about this. Off they come for a good scrubbing in hot soapy wwater