Pulled case bolts

[Eric Tyson]

Has anyone seen this before?
This is out of my bird, it is a C90.
I now have the through bolts and the heli coils in the new engine. I guess this is comon. I decided to rebuild the engine last fall after having an oil leak that I just couldn't find, I spent 3 days looking for it.

I lucked out and got a Case from Divco for less than it would have to send mine out for inspection, talk about lucky.

Eric

[Bird]

Re: Pulled case bolts

It sure looks like the bolts didn't go deep enough, looks like there is about another 1/2 inch they could have gone deeper, willing to bet that is what caused the problem.

[magman]

Re: Pulled case bolts

I'm betting you will use a CALIBRATED Torque Wrench when it goes together!

[Eric Tyson]

Re: Pulled case bolts

I'm betting you will use a CALIBRATED Torque Wrench when it goes together!

I am going with a high end engine shop, nothing cheep about it. They are even Balancing the rod assemblies by their CG

The new engine will be complete this Wednesday.

[Ragwing nut]

Re: Pulled case bolts

I have never seen that. That is not a common failure, something does look right considering that break is fresh, not one that is a fatigue crack and had been working for awhile.

[NY86]

Re: Pulled case bolts

I've see several of those in C85 and C90's. I think it is related to prop strikes. How about you?

Interesting, though, looks like it happened right before the teardown.

[Eric Tyson]

Re: Pulled case bolts

I would agree but i am still running the same prop that came with the plane and using it on my new engine. I have had 170 hrs on her in 4 years. Last summer I was on floats which make it very difficult to obtain the strike you are referring to.

[Eric Tyson]

Re: Pulled case bolts

I have never seen that. That is not a common failure, something does look right considering that break is fresh, not one that is a fatigue crack and had been working for awhile.

According to the engine guys it is common, the bolts that you see have been drilled all of the way through on my new engine so it now uses through bolts. They switche the later 0200's to the through bolts. The crack doesn't show well in the pics but the really shiny stuff was about the size of a dime. The crank is a first run and passed inspection, I lucked out and only had to replace the case and 2 lifters.

[magman]

Re: Pulled case bolts

Maybe I should have looked at pix first.

I have had O-200's pull out while torqueing.

Damage was strictly threads though.

[NY86]

Re: Pulled case bolts

The through bolt case was introduced at the same time as the O-200. From that point forward, all new engines and cases, regardless of model, had through bolts (on the center main). Converting old cases to through bolts is not a trivial undertaking as one of the holes penetrates the oil gallery. I've heard it has been done but don't know of anyone who does it. Divco has accepted cases like the one in the photo (including the two broken bits) as cores, so I assume they can repair them.

[Edwin Otha]

Re: Pulled case bolts

I've had one engine crack like that. I had an oil leak coming up through the base nut for the cylinder. Found the crack by removing the cylinder.
EO

[Edwin Otha]

Re: Pulled case bolts

After two fingers of Jack Daniels and finding my reading glasses, I'm not sure heli-coils are used on the case studs. Could someone have installed them as a repair?
EO

[Eric Tyson]

Re: Pulled case bolts

After two fingers of Jack Daniels and finding my reading glasses, I'm not sure heli-coils are used on the case studs. Could someone have installed them as a repair?
EO

The guys that are running the F1 engines are using through bolts and helicoils, the helicoils have a larger grab area which equals better grip. It appears to be comon on these engines talking to the guys at the engine shops.

[Len Petterson]

Re: Pulled case bolts

Now I am in trouble again: If helicoils where used and the bolts did not bottom out in the holes, the bolts would apper to be LONG!
Yes, helicoils have a larger holding area i the threads, but what is not what broke. The material holding the bolts broke away,
from over torque, sideload,vibration, age , your shoice, my guess.
But if the helicoil and bolt would have been longer and gone deeper into the case, would it have taken out more material or hold?
Offcoarse the through bolts would take care off this problem, but what about an old case in apperant good condition, visualy?
How about a die penetratent check before assambly?
Does the same problem show up in the A 65 case as well?
Len

[NY86]

Re: Pulled case bolts

I think when they talk about helicoils they are referring to the other studs on the front and rear bearings. Your assessment is correct; it is the web material that fails on the center bearing. Through bolts solve the problem by changing the stress on the webs from tension to compression. My theory is that it is caused by prop strikes, sometimes hundreds of hours before the problem is diagnosed. I've seen engines with mysterious oil leaks, engines with a lot of copper in the oil analysis, and engines with mysterious vibrations. Always there was a prop strike between the last overhaul and the diagnosis.

A little off the subject, but I traced a strange vibration in a C85 for a long time and couldn't pin it down. We finally decided to tear the engine down. When we did the crank came out in 2 pieces, cracked completely through the center main journal. It had been that way for at least 50 hours.