rusty cylinder

chimp koose · November 28, 2014, 12:23:21 AM

I am stripping down a 300 6cyl for a quick re ring and bearing to put in my 65 merc 1/2 ton. the engine will turn 1/3 of a turn and stop. I took the head off and there is a bit of rust in 2 cyl. The rust does not seem to have eaten away at the cylinders too bad but I want to remove it in the least destructive fashion. I am hoping to hone it and pop in some rings and not have to bore it. What have you tried that works to de rust the bores? Thanks in advance.

kb426 · November 28, 2014, 08:47:51 AM

Muratic acid or a berry hone.

Arnold · November 28, 2014, 01:14:51 PM

I like to get some carbon cleaner between the piston and walls..down into the ring area first and leave it a day or so.Then use some penetrant everywhere.Leave that a day or so.I like to clean the bores out with some type of solvent that dries well..like lacquer thinner to see what I have to deal with in terms of rust.
Rust..Depends on how much rust is there.As mentioned..one of those flex/berry hones.I have seen really rusted bores..like that last 2 stroke outboard I did that that hone would not touch. I am surprised that heavy duty rust remover dealt with.I try a rotary wire brush first..see how that goes.If ok then sandpaper.If chemicals are needed..then as mentioned..some type of acid. I have used really heavy duty rust remover.Good Luck.

chimp koose · November 28, 2014, 04:34:29 PM

I am nervous to hone as I don't want to open up the bore while knocking out the rust. Needless worry ?

enjenjo · November 28, 2014, 05:38:59 PM

Hone it enough to get the piston out, just a clean up. You don't even need to get it all. Then hone it to get most of the rust out, don't really worry about the pits. Get the rust out of the pits with a wire brush, then rehone, again not much.

How long do you expect this to last? I have done this with cylinders with some pretty deep pits, and just left them there. As long as the pits are not deep in the top inch or so, it won't be a problem.

I would use cast iron rings, it should be good for 20 or 30 thousand miles. If you want more, you are going to have to do it right.

I have also bored only one cylinder, as much as .060" more than the others with no problems in the way it runs. In that case you would need a new piston.

There is right, and there is what works.

kb426 · November 28, 2014, 07:21:07 PM

"There is right, and there is what works." I agree with Frank 100%. Lack of exp. and fear keeps people from a lot of repairs that are very effective. Run a race car for years and get an education and you fully understand that statement.

chimp koose · November 28, 2014, 10:26:30 PM

I have knurled pistons for a cheap low rpm rebuild and I have laid under a TAD and crocus clothed a torched rod journal while someone else had a ratchet on the blower pulley just to make the next round of a booking .I have done my share of 'farmer fixes' I was just concerned about how much material I would be removing along with the rust. I know this may have to go together a little loose but I do not want to re piston and I hope I don't have to knurl. The engine thats in the truck now runs ok but has an appetite for oil . I have this engine as a spare and if I can make it a decent runner I will put it in the truck . The pistons that are sticking are swinging through BDC and I can only turn the engine about 120 degrees so this is all near the bottom of the cyl .I will dingle berry hone it till I can get the piston out and then get picky with the rust. Thanks all for the suggestions.

kb426 · November 29, 2014, 08:25:51 AM

I have heard of people letting a cylinder sit for awhile with diesel fuel in it also. Trying not to destroy anything sure is challenging.

chimp koose · November 30, 2014, 01:47:06 AM

I got it ! I let it sit with about 1'' of wd40 on top of the piston overnight and it broke free. I had let it soak for nearly a week already but not with near as much wd40 in it as this time. Now the engine will turn all the way around . I have to go back to other projects for a while so I think I will let it sit with the wd40 in cyl and saran wrap over the top of the bores so it doesn't evaporate until I have time to get back to it. Thanks again guys for the advice

kb426 · November 30, 2014, 08:15:05 AM

Merry Christmas to you! I hope you didn't use up all of your good luck on one project.

jaybee · November 30, 2014, 03:48:00 PM

Careful with the WD40. My neighbor locked one up once using WD40 instead of engine oil for winterizing. It had been his practice to squirt a little oil in through the spark plug hole when parking the car for the Winter. One year he decided to use WD40 instead. By spring the aluminum piston skirts corroded, locking them to the cylinders.

chimp koose · November 30, 2014, 03:53:02 PM

Jaybee the head is already off . I am just using it too loosen things up. I used to use this stuff to put away my boat motor for the winter. I would pull the plugs and spin it over while spraying it in the spark plug hole . Come spring I would pull the plugs and spin it some more before trying to start it up. always worked fine for me.