torqueing engine case studs

[Guest]

Mechanics,

I am noticing that my C90 engine case studs at the front and rear bearing take 10-15 ft lbs of torque and keep turning with no real increase in torque.

I suspect that what is happening is that the studs are just turning thru the helicoils until the stud thread ride up next to the helicoil or the stud bottoms out against the bottom of the hole in the case.

The torque spec is 25-35 ft lbs for these 7/16" studs.

So I am going to use loctite on them and torque them to about 15+ ft lbs because I am afraid of damaging the case threads.

What is you experience with this stuff?

Am I being too gentile with it?

Advice appreciated.

Dave

[Ragwing nut]

Re: torqueing engine case studs

c90 and o200 have 2 floater thru studs at front and 2 in the rear. Hold the nut on the opposite side to torque them down.

[Guest]

Re: torqueing engine case studs

c90 and o200 have 2 floater thru studs at front and 2 in the rear. Hold the nut on the opposite side to torque them down.

Not so, C90 I have has two floaters at center bearing but I am not asking about those.

[astjp2]

Re: torqueing engine case studs

are the studs turning or just the nuts?

[Scott]

Re: torqueing engine case studs

The through studs feel a little different when torque is applied. This is because the stud is long so there is some stretch and twist. Set your torque wrench to the required spec and keep going til it clicks.

If and when you get them torqued, pay close attention to your oil pressure and screen. The main bearings have a required "squish." loosening and retorqueing the through studs, for example during a cylinder change, occasionally results in a bearing turning in the case.

[Guest]

Re: torqueing engine case studs

The question is not about thru bolts.

It is about putting the studs into the case half.

I repeat it here for convenience;

Mechanics,

I am noticing that my C90 engine case studs at the front and rear bearing take 10-15 ft lbs of torque and keep turning with no real increase in torque.

I suspect that what is happening is that the studs are just turning thru the helicoils until the stud thread ride up next to the helicoil or the stud bottoms out against the bottom of the hole in the case.

The torque spec is 25-35 ft lbs for these 7/16" studs.

So I am going to use loctite on them and torque them to about 15+ ft lbs because I am afraid of damaging the case threads.

What is you experience with this stuff?

Am I being too gentile with it?

Advice appreciated.

added picture of the studs in question

[Ragwing nut]

Re: torqueing engine case studs

Sorry about that. If torque is 25-35 lbs then crank them down. You should not be able to damage the threads. Looks like the case has been redone. Was the studs not reinstalled by the overhaul shop?

[Guest]

Re: torqueing engine case studs

Correct.

Originally they had been installed but the case had to be sent back 2 times for redos and during that process the studs were removed, loosened and so on.

So now I am checking them.

Dave

[Edwin Otha]

Re: torqueing engine case studs

I don't remember having heli-coils installed in the case stud locations. Most times the studs are oversized for proper fit. This area is pretty highly loaded for a thread insert.
EO

[Guest]

Re: torqueing engine case studs

I don't remember having heli-coils installed in the case stud locations. Most times the studs are oversized for proper fit. This area is pretty highly loaded for a thread insert.
EO

I think its a common practice by case overhaul shops.

[Edwin Otha]

Re: torqueing engine case studs

I've had a lot of cases overhauled and never had a question about that from the overhauler. I've used Divco, Crankcase Service, Chuck Ney and Nixon's. I'm sure your overhauler has the specs on it.
EO. Dave, I just looked in the O240 overhaul manual and they do,indeed, have a heli-coil repair for the case studs. Never have seen it done, live and learn.
EO

[Guest]

Re: torqueing engine case studs

Edwin,

I used one of the shops (I'll call them shop #1) that you mentioned for the original overhaul and the first redo. I also used another of the shops you mentioned (shop #2) to fix a bad insert that shop #1 did.

Actually the shop is not questioning anything, I am.

Have you ever checked the torque on the studs in a case you got back? What was it like?

I have the specs, they are in the OH manual.

The question is not about the specs as much as it is about your experience torqueing the studs into the aluminum case half. When I have a stud that just screws in at constant low torque and then all of a sudden abruptly stops and exponentially increases in torque it makes me nervous. It appears to me that the stud or thread has bottomed out.

I had to talk with TCM this am about something else so I also ran this question by them and they shared my concern. I have loctite-ed them and torqued to just short of the lower limit. That was also the recommendation of another shop (shop #2), not the one that did the overhaul.

Dave

[Edwin Otha]

Re: torqueing engine case studs

Dave,
I check them at 20 ft.lb for the small studs and 25 lf.lb on the large. And I have not found them under torqued from the rebuilder.
EO

[Guest]

Re: torqueing engine case studs

ahh...

Thanks Edwin, I think that all of mine were way under that so I guess that confirms that something went awry at some point during this case's repair process.

Dave

[Guest]

Re: torqueing engine case studs

Edwin & Mike,

Thanks again your experience helped.

I slowly worked up my courage to torque them down to the spec and got them to 25 ft lb for the big ones and 16 ft lbs for the small one.

Most big and all small came to a stop at 25 and 16 but on one or two big ones keep turning at 25. Nerve wracking for me.

Maybe I am to obsessive compulsive but they are in the range now so I can move on.

Dave.