Honing cylinder/piston

Andras, you may be thinking about this thread:

https://www.coxengineforum.com/t7586-did-i-ruin-my-brand-new-teedee-cylinder

Ken Cook described a honing method there, I tried it, it was a success

I have a couple of cylinders waiting in line for the honing treatment, nothing fancy, just plain old #2's, and I also plan to arrange a "marriage" or two.

Seeing that some of us are vastly spread apart, some suggestions on what to use might not be available to those across the seas. If I have to make an aggressive cut, I use rottenstone powder mixed with a lightweight 10w oil or 3 in 1 oil. I prefer this due to it washing out easily and not staying or imbedding in the cylinder. If I want to do a less aggressive pass, I prefer liquid abrasives made for silver or brass. I use Brasso but again I don't know if this is available to others.  These take more time but offer a more mirror like finish on the surfaces .  The tool I use to do this is a piece of 3/8" brass tubing. Seeing that the internal portion of a Cox piston is tapered, you can wrap a piece of tape tightly around the tubing and push it into the piston with the rod hanging inside the tubing. This allows you to rotate and move the piston up and down in the bore. Rubbing compounds work equally as well but I found these really need to be cleaned and scrubbed out with a old toothbrush. Don't leave any traces of residue on the piston or in the cylinder. Residue can easily get stuck in the ports of the inside of the cylinder. When the lapping part is complete, using a Davis Diesel wire bore brush can also assist the fit and break in as it leaves crosshatch marks on the inside of the cylinder.

To fit this new piston to your old cylinder, I would do all lapping with the piston upside down in the cylinder. Loosen up the bottom end real good and when it does slip in and out easily turn the piston back around and lap in the top without bringing the piston all the way to TDC. This will leave a good pinch up top. Remember don't go to far as it's much easier to take it apart and lap a little more than it is to go the other way. Ken

Thanks to all of you for the advice and links. I will try lapping/honing as you advised.

FWIW, I used "Autosol Chrome Polish" as lapping compound. It smells, looks and feels like just about any chrome polish, white, kind of tooth-paste like stuff. It is a rather gentle (or fine) compound, so using it will take time.

Maybe some fine valve-lapping compound would work for the more coarse work?

Thanks, Kari,

I also have some car polish fluid which I will check for its sensible (or rather, insensible) grit content before using it. Otherwise, I just noted the metallic top half of an old ballpoint pen will just fit inside the double-groove piston and serve as a dowell when gently turning the piston in the cylinder while lapping. (You must be inventive if you do not have a lathe, or other machining tools back home..)


BTW I have no idea for which engine this double-groove 051 piston may have been made, but for some strange reason it is a tad wider than the stock o51 piston hence my need for honing..I just bought it once on ebay in hopes it will swap with any 051 piston which are not easy to find anywhere...