Posted this over at steelsoldiers. Probably a bit more interest here though.
I found this tag on my engine. Thought it to be a rebuild tag.
Cylinders 0.020" over and rods & mains 0.10" under?
Looks to me the cylinders may have been bored .020" over and the original pistons were used. See photo. (Notice the gap between the piston and cylinder wall. The shiny part is the top of the top ring) My TM9-1840A says min. piston to cylinder clearance is .0002", max is .0012". With out using a micrometer, the flat feeler gauge between the two shows every bit of .0021" And no top ridge to ream out so it was bored to this size.
Any one seen some thing like this before? If the taper checks out OK, should I just get the right sized pistons/new rings for it?
Keith
1989-94 USN Active Duty Seabees
1953 M37 W/W
1946 cj2a project
The rebuild tag does, indeed, show a .020" over bore. If the proper oversized rings had been installed, you wouldn't have that obvious gap unless the ring was broken or stuck in its groove. Methinks a more thorough examination (with a micrometer) is in order here.
amanco wrote:Posted this over at steelsoldiers. Probably a bit more interest here though.
I found this tag on my engine. Thought it to be a rebuild tag.
Cylinders 0.020" over and rods & mains 0.10" under?
Looks to me the cylinders may have been bored .020" over and the original pistons were used. See photo. (Notice the gap between the piston and cylinder wall. The shiny part is the top of the top ring) My TM9-1840A says min. piston to cylinder clearance is .0002", max is .0012". With out using a micrometer, the flat feeler gauge between the two shows every bit of .0021" And no top ridge to ream out so it was bored to this size.
Any one seen some thing like this before? If the taper checks out OK, should I just get the right sized pistons/new rings for it?
If the bore is indeed .020" over, the piston & rings would have to be of corresponding diameter to give any decent service at all. Using a piston of a smaller diameter than the bore it's in would certainly be short lived.
MSeriesRebuild: if the bore is indeed .020" over, the piston & rings would have to be of corresponding diameter to give any decent service at all. Using a piston of a smaller diameter than the bore it's in would certainly be short lived.
I think that is why I am where I am. (With the engine out) I didn't let the engine grenade. I knew things just didn't sound right. Possibly right sized rings, wrong sized pistons? Any way, a rebuild is in order and I will keep you all posted on what I find. I just hope cylinder walls aren't scored real bad.
Keith
1989-94 USN Active Duty Seabees
1953 M37 W/W
1946 cj2a project
If the cylinders are scored to badly to be honed smooth, you still have two options. You can bore it out some more and install the proper size pistons and rings. The maximum overbore is .060", which is what mine is, but I believe Charles recommends sleeves with original size pistons & rings if you have to go beyond .040" oversize. Hopefully, you may be able to just "buff" the cylinders. Whatever the case, good luck with the rebuild and enjoy working on your truck.
Well, the more I took apart, the worse it looked. Every thing was just a time bomb waiting to happen. Starting with the clutch, the pilot bearing was loose in it's bore. Looks to be spun
The clutch disc was on the verge of going out on me. The flywheel was saved by total luck. I need to play the lottery. The rivets holding the clutch were just barely touching. The brass rivet shown has a high outer edge and it is just barely worn.
To my surprise three of the bolts holding the flywheel on were missing nuts and were loose and show signs of coming in contact with the clutch disc. Can't believe that didn't end in disaster.
#2 & 3 pistons both have failed piston pin retaining clips. And yes the pins and clip pieces gouged the cylinder walls.
Also had a spun bearing on the #4 cylinder though it had recently spun and not destroyed the bearing journal yet.
All bearings show signs of metal flakes impregnated into the surface. It was just a matter of time! Now if I can just get that 230 from k8icu, I can make the veteran's day parade on Nov 9th.
Keith
1989-94 USN Active Duty Seabees
1953 M37 W/W
1946 cj2a project
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