Cylinder Hones

[zul8tr]

Agreed, but what grits do you experts out there recommend?

Jeff

Here is a section from Blueprinting the 20H,

http://www.outboardracing.com/blueprinting%2020h.htm

but applicable to other engines:

Back then the hone with 4 stones and no wipers was recommended. Selected stones were 800 grit:


"HONING THE BLOCK: After doing some research on 2 stroke honing as to what you're really looking for in a good seal for a high performance 20H Merc, Oval F.Christner assured me that on a 20H stocker or gas mod or even an alky motor you always want to finish the cylinders with the very finest grit stones you can find! Also it is very important to "never" use a ball type hone or standard spring type 3 stone honing head on a high performance 2 stroke cylinder bore as both of these types of hones could cut 6 or more horsepower from your motor! It is strongly advised to use only a honing head that holds 4 stones with no wipers. These types of honing heads are very hard to find as even the Sunnen honing machine company only sells a 2 stone head with 2 wiper for even there most expensive type hoeing machines and this 2 stone head is not advised to be used on a 2 stroke motor. However, be advised there are honing heads made that will indeed hold 4 stones.

The next thing you need to understand, regardless of what the piston ring manufacturer tells you about a finish for cast iron rings, O.F.Christner told me you "always" want as smooth a final finish on the bores as you can get as that's for sure horsepower! At this current time, Sunnen honing machine company sells a 800 grit stone however they also sell a 1000 grit, but that's a special order stone. The ultra light round boss pistons I am going to use in this 20H are +.003 oversize from my bores that I now have, so I will start offwith the block clamped on the Bridgeport table and use a indicator to dial in each bore center. Then use a coarse 400 grit stone in the honing head to straighten up the bores and to cut some stock out. My finished bore size will be for a total of .007 piston skirt clearance. The reason for this number is because these cylinders have that much taper in them to get 100% clean up for the rings to form new seal on.I used lots of honing oil with the rough 400 grit stones to flush out the bore as the stones cut the cast iron out to within .001 of my final skirt clearance. Then I checked the bores with a dial bore gage in many locations, top, center, and bottom of each bore and then with the new pistons. After checking this I found I was forced to shim the honing head to get the stones to cut the cylinders perfectly straight. After getting the bores true and to within .001 of finish, I changed the stones in the 4 stone honing head to a set of 800 grit and took the bores to the finish size. Unfortunately the bottom cylinder did not clean up 100%. It was about 97 % cleaned up but this was fine as I will be hitting each cylinder again just a touch after I fit the rings with the 1000 grit stones set up in a drill motor just before I assemble the powerhead so this operation is now complete. I then washed the block in solvent and wiped it down with outboard oil then bagged it up for now. "