Lycoming O-145 Head Torque

[Bob Waldron]

I purchased a freshly overhauled O-145. It blew a head gasket in four hours. It pulled a stud out of the head. The mechanic helicoiled the head and replaced the gasket. Four hours later, the same head gasket is leaking. The mechanic tightens the nuts to 140 inch-pounds. This is the standard torque for 5/16 nuts that are 24 tpi. I have been unable to find any Lycoming specification for torque for the head. The mechanic is coming back next week to remove the head and replace the gasket and possibly replace the head.

What do others use for torque on these nuts, and were you successful?

[Bird]

Re: Lycoming O-145 Head Torque

Lycomimg service bulletin No. 125 dated Oct 1 1945 shows 5/16" nuts and cap screws at 150 In. Lbs, That is just a general recommendation though

[Pearson]

Re: Lycoming O-145 Head Torque

I don't mean to insult your intelligence, but have you confirmed the straightness of both surfaces? Also confirm you have the correct gasket. If the gasket is too thick, it will blow easier. Another point to ponder is that if the threads were weak, maybe the clamping force on the gasket was insufficient.

I had a problem with exhaust studs stripping out the threads in the cylinders. After about the third helicoil, I just said to heck with it, and did all of them.

[Howard Wilson]

Re: Lycoming O-145 Head Torque

Hi Bob,

I guess you looked at the old thread (listed at the bottom of this page) from 2006? Do you have the aluminum shims on your heads? Where did you get the gasket. I had Olsen's Gaskets make me up a few sets from an original that I sent them. Worked Great! They should still have the pattern. Just google them. I still think that a cut off 1/2 inch wrench is the best way to go on tightening the heads. One of the reasons I'm switching over to a continental was blowing a spark plug right out of the engine on takeoff, stripped the threads, engine sn505. Makes you start wondering how many mechs over tightened these things over 70+ years...... h

[Bob Waldron]

Re: Lycoming O-145 Head Torque

Howard,

Thanks for the pointer to Olsen's Gaskets. The gaskets on this engine were supplied by the overhaul shop. They did include the aluminum shims.

Sorry to hear about your spark-plug separation. If you are no longer going to be using your O-145, I would be happy to purchase your extra gasket sets.

I have been trying to come up with a method to check the head for flatness. I just now remembered that I have a piece of 1/2 inch steel plate that is drilled for the stud pattern of a O-145.

Thanks again.

[Howard Wilson]

Re: Lycoming O-145 Head Torque

Hi Bob.

Oops! Swapped the engine in a trade along with the gaskets..... Sandy Olsen was very helpful and patient. If he can't find the pattern send him a new gasket, or an old one with the correct new dimensions. He was apologetic when he had to raise his price to $12.50 each!!! I paid $140 for the last one I got from El Reno......There are still, probably, some people on this site with a cyl. head that they might part with......h

[wmfife]

Re: Lycoming O-145 Head Torque

Howard,

Thanks for the pointer to Olsen's Gaskets. The gaskets on this engine were supplied by the overhaul shop. They did include the aluminum shims.

Bob,

Did J. P. Hackenburg do your overhaul? I got three like-new overhauled heads from him with brand new aluminum shims after my exhaust sleeves burned off the originals (-at~50h. SMOH).

Wondering whether that's all the gasket I'll need or is the original type still being used? The paper ones? No one mentioned those and I had to do several google searches to even know they existed.

And what about gasket sealer? Is it ever used- or do I install them dry? I've located what looks like a good one but don't want to use it because it's an adhesive.

These haven't been installed yet and I can get the shim thickness if anyone needs that data.

(Oh and BTW I found a good deal on crowfoot open-end wrenches at Harbor Freight Tools.)

I do have an old spare cyl head not airworthy if anyone interested. RH I think but forgot whether F or R. (Cyl #?)

[Bird]

Re: Lycoming O-145 Head Torque

I sent you a E mail check that.

[Bob Waldron]

Re: Lycoming O-145 Head Torque

Bill,

Hakenburg is not the shop that I purchased the overhauled O-145 from.

Regarding gaskets, I assume that each head gasket consists of a copper/asbestos crush gasket and two aluminum shim gaskets. I don't know if you are supposed to put any sealer on the gaskets. I suspect not.

I have some 'shim' head gaskets that are .016 soft aluminum. I don't know what kind of aluminum they are.

I have never heard of paper gaskets for the heads. The gaskets under the valve covers are 'paper like' gasket material.

Be sure that when you install your Lyc O-145 that you have both foot-long support rods that go from the bottom rear of the crankcase to the bottom of the exhaust system. Lycoming mentions them and I never had them when I bought my flying airplane. They are VERY important, and keep the exhaust stubs from pulling out of the cylinder heads.

[Howard Wilson]

Re: Lycoming O-145 Head Torque

I have seen solid copper (almost a square cross section) head gaskets on a Lyc. O-145. Don't know if they are correct. But they were working. h

[wmfife]

Re: Lycoming O-145 Head Torque

Bob and Howard,

My rebuilt heads each came with the two flat circular aluminum shim gaskets surrounding one 1/8" wide copper ring of about the same thickness. The old heads I sent in to them had copper shims instead of aluminum. The shim material looks about like you describe, around .015 -.016 gage. There was no paperlike or fiber insert of any kind in either to my knowledge. I was formerly under the impression heads were attached with some kind of thin fiber crush gasket like asbestos but don't see anything like that.

The engine manual (p.24) refers to "...a cylinder head inner gasket in cylinder counterbore and two cyl. head outer gaskets over cyl. head studs..." and to assemble head "...with gaskets on cylinder barrel flange", but gives no further details. Wouldn't this thin copper ring be the inner gasket? The two aluminum "shims" are both perforated for the head studs. So I was originally under the impression they were the two "outer gaskets".

These rebuilds were so complete they even included the correct number of (inside) starloc washers (though I had a small supply) in ziploc bags along with the rubber rod-cover seals, induction hoses plus pre-installed fresh ground valves, springs, rockers and brand new shielded plugs and I am just thinking he would have included anything else that was needed. I could maybe give them a call to be sure but they appeared to have done everything else with the utmost in professionalism.

The IA mechs doing my last annual didn't know whether or not I should use gasket sealer. It didn't seem to matter much one way or another to them. On more than one occasion they've referred me to this list.

My engine did indeed come with the support tubes bolted to the oil pan for supporting the exhaust system. The only problem: they were about 3/8" too short. That's almost exactly 2X the distance off the heads the stacks- all four of them- were. On at least one the sleeve was burned completely through when I finally discovered them.

The shop had drilled and pinned these hollow rods with small screws but never raised the system and it's at best a half-measure now. So I need to fill the holes they drilled and extend the tubes /rods to the correct length after I expand the stack ends to fit up tight around the sleeves. The rod ends should bottom out on the spurs for full support, but it appears they were either cut at some time or never made to do that. The head sleeves unlike the rest of the system aren't stainless, not even the replacements in now. Corrosion-X is standard equipment here this close to the Gulf.

He also (Hackenburg) suggested using worm-screw adjustable SS band hose clamps around the entire system for added support. Or maybe braided cable or light chains. I am looking into all that- if it can be done safely.

My one remaining original cylinder head now has a stripped plug hole (discovered by yours truly). Logs show helicoils had been installed before on one or two prior to purchase. I always torque plugs to no more than 40 i.p. as that's what I got on breakaway the first ones I took out and on most since.

Maybe I should go for my A&P then I'd be sure my mech knew my A/C as well as I do.

[Bob Waldron]

Re: Lycoming O-145 Head Torque

Bill,
If your solid copper gasket is about 4 inches in diameter and about 1/8 inch wide and 1/8 inch thick, you probably have one like Howard mentioned above. I don't know if these came from Lycoming, but I have a friend who ran a machine shop who said that they used to make make solid copper gaskets for Corvairs, to prevent them from blowing the original styled gasket. I had a few made up by a friend who is not interested in making any more. I installed one, and it worked well.

Regarding the exhaust support tubes, I manufactured mine so that there was a washer welded to the tube (an inch or so from the end) and this washer supported the bottom of the spur on the exhaust pipe. In other words, the end of that support tube, never touched the exhaust pipe. The support tube 'slips into' the spur, and is not pinned to it.

[wmfife]

Re: Lycoming O-145 Head Torque

Hi, Bob,

I just made a discovery just now. Yes - that 4" copper ring is right at 1/8" wide but not as thick - more like 3/32" if I am measuring it right. -But, it isn't solid. It's in fact two paper-thin copper rings with a fiber core sandwiched in between. I wouldn't have noticed this without using a hand lens and a good light. Thanks.

..So that's where the crushable fiber gasket was hiding. And no, Lycoming didn't manufacture this one but Hackenburg does hold the T.C. for the O-145. The parts are legally re-manufactured not replacements. I have his address.

As for the support tubes - I can see how that would work fine for your setup but seems mine is just a bit different. The tubes are larger diameter than the spurs! So they fit around them not inside! *Ergo* ~ someone will be welding an oversized tube section on the ends of these before I do any flying. And I would like to see a ref. to all this in the handbook literature. So far I haven't.

This does answer a lot of lingering questions and hope I didn't jump anyone's thread. It's just that an engine that sits too long becomes a spare parts collection and that's no way to treat a low-timer like mine. It's getting kind of desperate around here.

Thanks! I hope everyone benefits from all this. It seems they improved this little add-on as they went along. And I do highly recommend Hackenburg Aviation for O-145 maintenance.

(Keeping the Corrosion-X handy and applying liberally...)

[flylo]

Re: Lycoming O-145 Head Torque

If anyone needs them I have several engines & parts available. Several good heads.

[Bird]

Re: Lycoming O-145 Head Torque

Can someone post some pictures of the support tubes?