O-200 case splitting

[Eric Brown]

Having trouble separating my O-200 case halves for overhaul. No info on Harry Fenton tips. ALL bolts removed. All thru stud nuts removed. Case will separate slightly at rear. Will not loosen at front. Any ideas that won't damage the mating surfaces ?

[CarlOrton]

Are you *sure* you got ALL the bolts? There's one right up at the front, right by the prop flange. I *think* it's on the underside, but with the engine on a vertical stand, I won't swear by that. Don't ask me how I know about that one... I completely missed it. Same frustration you're having. Once that last bolt was out, it just about fell apart. I was impressed with how easily it split, *if* the prior sealing was done IAW the manual.

About the only other thing I can think of is that the oil seal at the very front of the case around the crank is glued into the case (well, sealant), so if that is especially stuck in there, I can see where it might give the illusion of a stuck case.

I just split mine in December, so am a bit familiar with your plight.

[Eric Brown]

UPDATE; was able to separate case 1/16"all the way around. Most difficult at front end. Still will not separate any further. Trouble seems to be at lower thru stud ahead of #4 cylinder.

[Sam Buchanan]

The through-studs are an interference fit at the case joint line, may be necessary to gently drive them out of the case.

[Eric Brown]

UPDATE; Got the case split apart. The problem was at the cylinder #4 hold down fwd thru studs. The upper stud had broken off about 1/4" below the 1-3 case half and the lower stud had pulled 1/4" out of the 1-3 half and was working its way into the 2-4 half which caused the separation difficulty. Looks like an expensive over torque issue.

[CarlOrton]

Yikes! Sorry to hear that. Good news is that just about anything can be fixed or replaced, although at a cost. If damage limited to the studs, that's pretty straight-forward and is normally addressed by places like Divco during their case renovation.