Cylinder to case gasket fail

Peanut said,
"looks like someone has taken a deburring drill to them which has seriously reduced the gasket surface area around a couple of the holes."
Yep, but these are factory or from a previous shop because the feller that owned this before me couldn't thread a nut on a bolt.
I do chamfer my bolt holes it they are threaded. I think as Jim has mentioned before, torque can raise an area around threaded holes that interfere with sealing of gaskets. Plus it just looks more professional and keeps the bolt from pulling up the top thread.
Thu
P.S. Good eye Peanut!
 
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Oh yes indeedy they're bad! The only worse garage vermin are steel rats. Those critters can mess you up two ways. They scarf up tools, tins, and fasteners and shit BBs--gotta watch your footing or risk a nasty fall.
 
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Don't forget the "Grease Worms!" They drag their little butts all over your chrome, get behind nuts, down in fittings, on your pipes, inside head light buckets, rusting up everything!

(I used to think everyone here was crazy because I was drinking. But I haven't had one drink all day and nothings changed! :laugh:)
 
Do these long studs get anywhere near their yield strength when torqued fully? Is there any possibility that they lose their clamping strength after multiple engine reassemblies and re-torques? I don't imagine ARP makes a new stud kit...?
 
gggGary said:
Haven't seen a stretched stud yet. IIRC there were high tensile studs for race motors way back in the day. but not anything recent that I'm aware of.
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Yeah... I'd guess you'd pull the threads out of the cases long before you reached the yield strength of the studs
 
Curious here. The bolts on GoldWing heads are intended to stretch....so they are re-torqued with new grease on the bolt threads. Shouldn't the XS studs/acorn nuts be torqued/re-torqued with new grease on the threads also?

Scott
 
mrtwowheel said:
The bolts on GoldWing heads are intended to stretch....so they are re-torqued with new grease on the bolt threads. Shouldn't the XS studs/acorn nuts be torqued/re-torqued with new grease on the threads also?
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Stretch bolts are not usually re used because (stating the obvious?) they have stretched. Have a read of this.
You should always lubricate a thread before torquing unless told not to do so.
 
Max Midnight said:
Stretch bolts are not usually re used because (stating the obvious?) they have stretched. Have a read of this.
You should always lubricate a thread before torquing unless told not to do so.
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I think this might be a good place for clarification. To the best of my knowledge, torque specs are always for clean, dry threads, unless otherwise specified. I'm 100% sure this is true in the aviation industry. My Moto Guzzi service manual has a note in the front that says the torque values are lube torque, and I believe the lube is specified. In Gary's post, a lube is specified for the head bolts. So, I believe the truth is just the opposite of what I quoted, unless there is a machinist standard I'm unaware of. Unless I can be corrected, UNLESS OTHERWISE SPECIFIED, TORQUE VALUES ARE FOR CLEAN, DRY THREADS. I know we were speaking of head bolts, but I didn't want to allow what I considered confusion to stand.
 
Even though I lube or anti-seize most all of my threaded fasteners, spark plugs are something I don't. I know many recommend anti-seize on the threads but I tried it and found that basically it just gummed them up. Clean, dry ones always worked better for me.
 
5twins said:
Even though I lube or anti-seize most all of my threaded fasteners, spark plugs are something I don't. I know many recommend anti-seize on the threads but I tried it and found that basically it just gummed them up. Clean, dry ones always worked better for me.
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Count me in the camp that lubes everything. Dry threads are a breeding ground for corrosion. We've all tore old bikes apart and found fasteners badly corroded.
But... as Marty (correctly) points out above, about every torque chart you find calls for "clean dry threads." Therein lies the rub. Bell Helicopters did a study years ago after losing too many helicopters due to bolt failures. They found that, contrary to published tech data, mechanics were lubing the bolts in the rotor mast prior to torquing them. Their study showed that lubed fasteners had anywhere from 20 to 40% more tension loaded into them than un-lubed fasteners. With that in mind, I tighten everything to about 75% of published torque. Sometimes even less.
On plugs, I use a high temp thread lube... Ease Off 990. Yeah, it's leftovers from the airplane days. It's rated to 1100°F. Last time I looked it's about a hundred bucks a pint. I've got a lifetime supply, but I'm sure there's a cheaper alternative out there.
 
Here's a NASA study on lubed vs. un-lubed fasteners.

nasa1.png
nasa2.png
 

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Raymondo said:
Gosh, it really is rocket science:yikes:
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Ohhhh, you betcha! I believe that is Robert Goddard in the right upper right corner with one of his first rockets.

The long studs are the problem. They have more stretch and give simply because they are long. But it's the twisting on loosening or tightening that makes it feel like your about lose one. When you torque them, they end up sticking and you have to "break them Loose". It is the friction of the threads that cause the stick and eventual galling. If I use anti-seize I can get through all my re-torques without removing the nuts or whatever. Even then some will stick or take a set. I caution everybody not to just adopt what somebody else is doing. There are a lot of variables with the stud and nut you looking at. Don't just slap some oil or anti-seize on the stud and torque it down to 30 FT LB cause somebody else did it that way. Us old farts have developed a feel and an eye for what we are doing and our way of doing it. Take your time and go slow. Learning how to install a heli-coil, or worse, is a lot harder than thinking, hummm, that stud is a bit rusty. I'll clean it and use a drop of oil to help it take the strain of it's buddies.
Thu
 

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