Thru bolts and torque sequence & oil pump cover

How to keep the Cessna 170 flying and airworthy.

Moderators: gahorn, Bruce Fenstermacher

Thru bolts and torque sequence & oil pump cover

Postby twlareau » Mon Sep 03, 2012 3:50 am

Hello everyone,
I'm the guy that was lucky enough to find the cracked lifter bodies in my C-145.
I have gotten all the parts back from the various FAA repair stations and we are getting ready to put the engine back together. I have read the overhaul manual several times and am unsure of how to torque the case halves together. My concern is that I don't want to possibly spin the main bearings when I torque the thru bolts on the cylinders. I called Continental and asked if a service bulliten existed that would show a torque sequence diagram. The tech person indicated that nothing of that sort existed. The manual calls for tightening the flange bolts, bottom thru bolts and then install the cylinders. Would it be prudent to install all the cylinders (loosely not torqued) first and then after all cylinders are installed torque the cylinder thru bolts without moving the crank shaft? Is there a risk that a main bearing could shift out of position with just the lower thru bolts and the flange bolts torqued? I was thinking that I could put a stack of washers on the cylinder thru bolts and torque them down without the cylinders installed and then put one cylinder on torque to spec go to the opposit side of those thru bolts and install that cylinder and torque that one to spec. I think I'm getting a bit rapped around the axel on this one but don't want to take the risk of wrecking a good engine.

When putting the oil pump cover on should I use Locktite 515 gasket eliminator? The manual says nothing about using a sealant but Continental SIL 99-2B says to use it (all models). Again, I talked to the Continentl service rep but he was unsure. I dont want to get the Locktite into the gears. I did use machinest blue to check the fit of the cover to housing and it was a perfect fit, no gaps.

Thanks for the help!
Thad
User avatar
twlareau
 
Posts: 65
Joined: Fri May 13, 2011 3:20 am

Re: Thru bolts and torque sequence & oil pump cover

Postby Aryana » Mon Sep 03, 2012 5:59 am

As I remember assembling it with my mechanic, there was no sealant on the oil pump cover as the gears were lubed with a bunch of oil and torqued down to spec.

I was lucky to have a mechanic who has been rebuilding Continentals for many decades help with the order of torquing the through bolts. I remember him discussing some tricks that were not outlined in the sparse overhaul manual. Don't turn the crank until everything is installed and torqued down. I do know that you shouldn't need to do your washer stack idea to get it torqued properly.

Some old timers gave me some great advice on the O-300 regarding the overhaul manual..."it's easy to build one up with the instructions in the factory manual, but it will take you years to learn how to build a great engine with all the little tricks that give you the best chance to have one that will last."
1955 Cessna 170B
User avatar
Aryana
 
Posts: 2358
Joined: Sun May 15, 2011 7:21 am
Location: Half Moon Bay, CA (KHAF)

Re: Thru bolts and torque sequence & oil pump cover

Postby Bruce Fenstermacher » Mon Sep 03, 2012 1:35 pm

Thad,

You will not go wrong following the overhaul manual and subsequent SBs exactly. The main bearings will not spin. Do not over think this.

As for the sealant on the oil pump gear cover I've done it both ways. I would only use the thinest amount of sealer on the outside of the pump housing if I used it at all per the SB.

Lets see if I can describe this right. The oil pump does not rely on extremely close tolerances and a seal to work sufficiently pumping enough pressure to these engines. This is not to say you want to assemble and run one that does not meet the tolerances. Ask yourself this. What is sealing the drive shaft around the cover. No sealant worked fine for years until they wrote the SB and still will.

Oil pressure loss it woulds seem is rarely the fault of the wear of the oil pump but rather worn main bearings to a point that exceeds the pumps capability. This is kind of a built in warning in that if you have low oil pressure it's more than likely time to replace the main bearings and or crank. Unfortunately I'm speaking from first hand experience.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, President, TIC170A
Email:
N7A '49 170A -More original than most making folks GREEN with envy
N42532 '45 J-3 Clipped Wing Cub
User avatar
Bruce Fenstermacher
 
Posts: 7747
Joined: Tue Apr 23, 2002 11:24 am
Location: Telford, PA Based at UKT

Re: Thru bolts and torque sequence & oil pump cover

Postby twlareau » Thu Sep 06, 2012 12:33 am

Thanks to the both of you for the help. I think I was over thinking the assembly. We start putting the engine together tomorrow. I will keep the updates coming.
Thad
User avatar
twlareau
 
Posts: 65
Joined: Fri May 13, 2011 3:20 am


Return to The Hangar

Who is online

Users browsing this forum: No registered users and 1 guest