The Stovebolt Site Forums The Shop Area Engine Shop Honing advice

I'm an experienced machinist but not so much with automotive machine work. I bored my 270 block for .020 over pistons and left .005 for honing. In hindsight I probably should have bored within .002 or .003.
I'm hand honing with a Goodson hone (clone of a Sunnen An-112)

My problem is I'm getting some taper with the bottom of the cylinder being .0005-.001 smaller than the top. I'm extending about an inch out the bottom of the bore, which is as far as I can go without hitting the main bearing webs. I've tried dwelling at the bottom but it seems by doing that the center of the bore starts to get larger.

The cylinder gets warm during honing so I have to wait for it to cool to get a good measurement. It does seem to measure a little straighter cold than warm.

I have considered setting the boring bar back up and sneaking a little more out of the bores.

Any advice on technique?

BTW: I did discover that it's possible to flip the stones end-for-end and run the hone in reverse. When using a honing machine it's good practice to flip the part regularly to keep the hole straight and stone wearing evenly, but I'm not sure if it's helpful on an engine cylinder or not.

That's a pretty common problem- - - - -and I've been fitting pistons that way for a little over 50 years! You're on the right track by concentrating on the bottom of the holes. Don't worry about maintaining a good cross hatch pattern until the final few passes- - - -it won't hurt to let the hone spin at the bottom without oscillating until the hole is almost the right diameter. You can also put a short piece of .001" shim stock between the bottom of the honing stones and the hone assembly to preload the bottom of the stone a bit. I learned early on to bore the cylinders to the exact piston diameter, and put the specified skirt clearance in by honing. That's plenty sufficient to eliminate any machining marks left by the boring tool. If you happen to have a carbide "button" hone available, running it fast with motor oil as a lubricant and moving it up and down rapidly puts a very good cross hatch for ring seating in the cylinder as a final operation. It won't enlarge the hole at all. Have fun!
Jerry

My sunnen stones are glued in the holders so I don't see a way of shimming the stones out at the bottom.

OK- - - - -I use a Regis hone, and the stones clamp into the hone assembly with setscrews. I can shim a stone that's worn unevenly to compensate for wear.
Jerry

That's a possibility...did a quick google search and it looks like some Regis stones are compatible with Sunnen AN-112. I'll dig into it further.

OOPS! Mea culpa! I was thinking of the AMMCO hone I had before switching to the Regis that I use now!

www.ebay.com/itm/177899337841?

My hone is getting old and tired, sort of like me! Here's a brand new setup made in India that looks to be very high quality, and it uses stones similar to the AMMCO type. If I get into building stovebolt engines again on a regular basis, it might be worth the cost.

www.ebay.com/itm/146138989077?

Jerry