Piston problems

[ahhudgins]

Originally Posted by Rossterman

If bores are good, hone and put in new pistons and rings along with rod and main bearings. Parts are pretty cheap for these engines and aren't marine specific.

X2 on that and what CantRepeat said. If you're into the engine that far, I would do the hone/bore and replace bearings, pistons and rings.

[1redTA]

i would get a rebuild kit from jegs or summit with new pistons, rings, bearings, oil pump and blah blah blah it would
be cheap insurance

[CantRepeat]

Originally Posted by 1redTA

i would get a rebuild kit from jegs or summit with new pistons, rings, bearings, oil pump and blah blah blah it would
be cheap insurance

Yup, you can get some screaming deals buying a master kit.

[strad]

A bit of anecdotal experience here. I pulled the head on my BMW M20b25 engine (92 325i cabriolet) b/c it was leaking oil (common problem with an older M20) and I discovered damage to two piston tops similar to the first pic you posted op. My guess was that the engine was running lean and blew apart the insulators on a couple of the spark plugs. The white ceramic bits banged around in there and dimpled the tops of the pistons. I only guess this b/c right after buying the car I replaced the plugs and noted that some were damaged, and I noted which cylinders they came from.

Anyways, cleaned them up, put it back together, and it's been fine. There is about a 10 psi split between highest and lowest cylinder compression. The cylinder walls on those cylinders were damaged by the debris too, but the engine doesn't consume oil and compression is within spec, so I'm running it that way. I've since had the injectors refreshed, which should cure whatever lean issue the engine might have been having.

[jfw432]

Yeah I got my entire kit minus pistons and oil pump from summit. Guess I can order some pistons too. Are the wrist pins pressed into the rod? That's the only thing I can figure. Any tips on removing them?

[Kyle]

Originally Posted by jfw432

Yeah I got my entire kit minus pistons and oil pump from summit. Guess I can order some pistons too. Are the wrist pins pressed into the rod? That's the only thing I can figure. Any tips on removing them?

Yes they are pressed in.

Take the new pistons and the rods to a machine shop and let them press the new ones on. They will do it a lot faster and you won't have to rig something or beat the pistons up trying to do it by hand.

[CantRepeat]

I'm sure the machine shop will tell you but, don't forget new cam bearings while you have the motor torn down; freeze plugs too(brass).

[CantRepeat]

Originally Posted by jfw432

Yeah I got my entire kit minus pistons and oil pump from summit. Guess I can order some pistons too. Are the wrist pins pressed into the rod? That's the only thing I can figure. Any tips on removing them?

They are pressed in and most machine shops heat the end of the rod a little before pushing the pins back into the new pistons.

[jfw432]

Originally Posted by CantRepeat

I'm sure the machine shop will tell you but, don't forget new cam bearings while you have the motor torn down; freeze plugs too(brass).

Got 'em but thanks for the reminder. Had to buy a used cam bearing tool though because I didn't have anything like that in my arsenal of tools.

[Dino Don]

Check cylinder wall taper. If 12 thousands or greater bore it the ring mfg will not stand behind rings to seat in.