Have a few engine blocks laying around.
A couple of interest have rust in the cylinder bores. Discovered the rust after pulling heads off. My first thought is to take a penetrating oil (or transmission fluid) and a scouring pad to them and see how well they clean up.
Anyone have a better proven method -- preferably with a power tool involved?

 

Yea – I know what you mean.

I don't know if it's better, but:
I usually take a 1/2” diameter x 12” long wooden dowel (one that will fit my chuck – you could have 3/8” or 3/4”) then saw a slot along the length of it down the center about 3 inches long. I then take some fine steel wool and cram into that slot – as much as it will hold without fear of cracking the dowel. I then coat it with Marvel (but any good, thin oil should work) and slap into my drill motor. After honing the cylinder a little I check to see if it’s pitted. If not I continue to shine it up.
Some of the steel wool could breakdown and get into the oil that’s collected on top of the piston, so make sure you can get all that out. If it’s a naked cylinder, though, I guess there’s no problem with that.

However, they do make a hone just for this that will fit a drill motor. I would guess any parts store would carry them. I don't do much of this, so I just go with the dowel and steel wool.

 

To do this right you will need to pull the pistons and and preferably the crank.

There are cylinder hones available that look like giant bottle brushes with ***** at the ends of the bristles. Find one that is the right size for your cylinder, put it in a good electric drill, bigger is usually better.

Then put that baby in the cylinder and move it up and down thru the bore. You want to see about a 45 degree cross hatch after you are done. Works great and doesn't take long on a cylinder in decent condition. While you are at it, you should mike the cylinder and then get rings and or pistons to match.

I forget the name brand of these hones, but you should be able to find one at a good supply store. You might even be able to rent one since they last a long time and you probably only need it once.

Good Luck,

Jim Henderson

 

I think these hones ARE called bottle brushes. Or glaze breakers.

There are also thingies that have 3 little honeing stones on them that goe into a drill. They have a flexible shaft and the stones will slowly extend with the speed of your drill. Stick them in the bore, turn up the drill and move them in and out.

Those are really cheap, but I belive that the cross hatch pattern is much more desirable.

 

Well, you're not really trying to hone the cylinder as much as just remove the rust. For a hone job, as Jim says, best to pull it apart to do it right, but if you just want to get rid of the rust for now, till you're ready to use the engine, I would spray it down with WD-40 or some similar product, and go for the scouring pad treatment. I don't think I'd really want to use a hone with the pistons still in place, although I have done so before. Here's what I did one time: I had a car that I had gotten out of someone's back yard for free, just for parts. The engine was frozen up and one day I decided to see if I could get it running cheaply. I pulled the head and found that 2 of the 4 pistons were stuck, but nothing looked too bad. I sprayed WD liberally in the cylinders and stuck a 2X4 block in on end, and tapped on it with a hammer while I tried to turn the crank by hand (by foot, actually. My hands were busy!) Switching back and forth between the two stuck pistons, it broke free. I turned it over several times, then sprayed in more WD and lightly honed the cylinders till the rust and junk was off the cylinder walls. Then I switched to carb cleaner, and sprayed it clean after hand wiping as much crud out as I could get. I would then turn the engine by hand, and as a piston came up in the bore it would push crap up and leave it on the cyl. walls as it went back down. I just continued turning the engine and wiping out the crud until all 4 were clean and no more crud was deposited on the walls when the pistons went back down. Pulled the motor, stuck it in the other car, bolted the head back on with a new head gasket set, fired it up, and drove it to Olympia Washington and back that weekend (From Redding, Calif.) Started to burn oil and smoke a bit after about 6 months, rebuilt it (without boring out) and it still runs great more that 20 years later. -TD