Alright. So the story goes like this. Buddy of mine rolled over his 300 in the water. Water got in the engine and he ran it back to the truck. Anyhow, it went to smoking. So we tore it down and I had the cylinder miked and it was out of round. So I had it bored .020 over and put a new piston and rings valve seals and gaskets. So the top end was fresh. Cranked it up and it smoked a bit which I wrote up to being the oil in the cylinder. Well we ran it for about 5 minutes and it only got worse. Tried adjusting valves and anything else we could think of that would possibly make it smoke. But still smoked with about 2 hours of total run time on the new top end while we tried everything. So we went ahead and took it back down and checked into it farther. Split the cases. There was quite a bit of mud and sludge at the bottom. Turns out the crank bearings were in fact bad. But we went ahead and replaced all the bearings in the bottom end and put it all back together. Cranked it up today for the first time and everything was good. Then after 5 minutes or so it started to lightly smoke then got a bit worse but not like it had before. So, my question is, would that couple hours of run time with bad crank bearings put enough wear on that cylinder to make it smoke again already??

 

My guess is yes. That mud and crud getting thrown on the cylinder walls is like sandpaper. Wouldn't take long to scratch the walls in that case. Did you give the guy that bored it .020 over the piston? That's always best is for him to have it in hand when he does the bore job. Did you also replace the rings?

 

Yes I gave him the whole piston kit when he did the bore and hone. I've had him do 4 or 5 bores for me already with no problems so I'm sure that he did the work correctly. But it just seems to me that with that little bit of run time it wouldn't be that bad. But maybe so? I did the same top end procedures as I've done before while putting it together. I think I'm going to bring the cylinder back to guy to mic it and go from there?

 

I bet that if you take the jug off and look at it, it will have scratches all over it. With mud in the case, it can do damage in 10 seconds.

 

Well that's what gets me. When I took it off to do the bottom end rebuild I looked at it for scratches and didn't see any. But I did hear what sounded like a light scratching sound in the cylinder area while I had it idling when I got it cranked back up yesterday. But I haven't pulled it back down yet to check it out. Maybe I can get lucky enough to get away with a hone??

 

Maybe.

 

Yea probly not though lol. Ill just have to get it miked