O-145 head bolt torque

[flylo]

Can anyone tell me the head bolt & rocker box cover torque for a Lycoming O-145?

[Bob Waldron]

Re: O-145 head bolt torque

Eric,

I am interested in hearing the correct answers to your torque questions. I tighten the heads to the ft-lbs specified for that size stud (I don't have the number here). I re-torque every 25 hours.

For the rocker arm covers, I apply very little torque. Most apparent rocker arm cover leaks are really leaks around the rocker arm plugs on the side of the head. For the rocker arm cover, I use a Permatex product called Hilomar HPF (or something like that). It never hardens and you only need a very thin film on each surface. I use hand made gaskets that are about as thick as two sheets of paper. My valve covers NEVER leak.

I am waiting to hear what others do.

[flylo]

Re: O-145 head bolt torque

Bob,If you can find what you torque to,let me know.I just want to check the torque at every oil change.Also I just e-mailed the pics you needed.Let me know you got them OK.Thanks! Eric

[Howard Wilson]

Re: O-145 head bolt torque

Tight enough and stripped!!!

On the head nuts using a short (3-4") handle box wrench you can feel a point where it doesn't want to turn anymore. That should do it. Then after 3-5 hours running time do it again. This was the method shown to me by two different IAs.
Don't think that you could get a torque wrench in there??? I've had to grind down the 1/2" boxends to almost nothing to fit between the nut and the head casting. The Lycoming overhaul manual just says: "tighten evenly using box wrench."
The rocker covers are easily warped by overtightening. And those things love to leak. I just snug them up enough to compress the gasket and squeeze out a little of the high temp silicone. Lycoming manual says: "Tighten covers, using No. 10 plain washers, and plain nuts." hmmm maybe we weren't so litigous back then.

Well, in looking at the service bulletins in the back; here is SERVICE BULLETIN NO. 125 dated October 1, 1945 supersedes NO. 109 & 21.
Subject Revised Tightening Torque Limits.

an excerpt: "There are certain places on the engine such as rocker box covers where it is undesirable because of soft gaskets or other conditions to give definite values for tightening torque. Under such conditions it is necessary for the mechanic to exercise some judgment to avoid overtightening or undertightening nuts or capscrews."

This service bulletin also lists general recommendations:
10-32 nuts and capscrews-----------------30 In. Lbs.
1/4" nuts and capscrews----------------75 In. Lbs.
5/16" " " " ---------------150 In. Lbs.
3/8" " " " ---------------300 In. Lbs.
7/16" " " " ---------------400 In. Lbs.
1/2" " " " ---------------550 In. Lbs.

Everyone: I've pulled this from a 83rd generation photocopied Lycoming manual dated January 1947. I have not looked for revisions on this information, it may be obsolete for flight use, and of historic interest only.

[flylo]

Re: O-145 head bolt torque

Thanks Guys! My manual is a 1942 & lists everthing but torque(must not have torqued things in '42).Any chance I can get copy's of revisions & service bulletins to put with my manual? Thanks Again!

[Howard Wilson]

Re: O-145 head bolt torque

Probably a good chance Eric. PM your address to me again. Howard

[Bob Waldron]

Re: O-145 head bolt torque

Eric,

I tighten my Cyl Head nuts to 140 inch pounds. I use modified 4" combinaiton wrench. I cut off the open-end off of the wrench and ground the box-end way down. I drilled a 3/16 hole in the end of the wrench. The hole is exactly three inches from the center of the 'box'. I hook a 50# fish scale to this hole. By pulling the scale to 40#, I get 120 inch pounds of torque.

I have stripped a stud on a freshly installed head (and said some words that are not to be repeated in mixed company). I now remember to test each stud to 150 inch pounds prior to installing a head. For stipped studs, I purchased some longer helicoils. Standard length helicoils are 1.5 times the bolt diameter. The longer ones are 3 times the bolt diameter.

[flylo]

Re: O-145 head bolt torque

Great idea Bob! I was going to try to modify a sheepsfoot & use a small torque wrench,but I like your idea better. What do they say about the mother of invention?

[George Hvizdak]

Re: O-145 head bolt torque

Bob,

What type of lockwasher (if any) do you use under the nut on head when torquing? On all three of my engines had different styles- thin external star,
stainless internal star....

George

[Bob Waldron]

Re: O-145 head bolt torque

George,

I have seen all the various lock-washers used. I am using internal-star ones. No good reason. They all hold real well for most of the studs. The ones that cause me the biggest problems are on the rear two cylinders. Once you get used to torquing at each oil change, it is no big deal.

[galtdurnford]

Re: O-145 head bolt torque

Hi All, I've noticed when setting the valve lash on my lyc. 0-145 that the clearance always tightens up approx. .002" or so every 40 hrs. Is this what one should expect from your experience. Cheers, Galt.

[Bob Waldron]

Re: O-145 head bolt torque

Galt,

I am sure that I have had one or two tighten up over the years, but many more are a little looser, and most of the time they remain the same. My O-145 is open to the wind (no cowl). I don't know what would cause the valves to tighten up routinely. You might want to check them an hour after you set them.

[Howard Wilson]

Re: O-145 head bolt torque

I have to remind myself to reset the gap after retightening the head bolts when the engine has 3-5 hours on a head replacement. Bye the way: now that you Lycoming guys are looking at this, who wants to sell me one of their unused head gaskets made from unobtainium? It's the only thing keeping the plane on the ground.