Torque Specs

[Dean3326]

Need the torque specs for a Lycoming straight eight model 4HM    need for the head  intake and exhaust

Thank you

[JV Puleo]

Torque specifications are a function of the diameter, thread and composition of the studs or bolts. You don't say what this is for, but torque wrenches are a fairly modern invention. Google "torque specification chart." It has little or nothing to do with the make of the engine.

[Spinneyhill]

According to this thread, http://forums.aaca.org/topic/244378-which-straight-8-lycoming-engine/, Lycoming 4HM were used in 1927 and early 1928 Gardners.

 

http://www.gardnermotorcars.com/tech/Auburn/Gardner_Engines-2.pdfgives a few further models using the 4HM engine.

Edited August 5, 2015 by Spinneyhill (see edit history)

[dictator27]

"Run it up until it's tight and give another half turn."  Advice given to me by an old time mechanic 50 years ago.  Somewhat tongue-in-cheek maybe, but he never used a torque wrench.  He didn't own one.

 

Terry

[JACK M]

I was told just a bit before it breaks.

[vermontboy]

I always went snug, then a hard straight pull, then a tug. Haven't blown a head gasket or broke anything yet. And it is very close to 1/2 a turn past snug.

[Dave Henderson]

Mechanics of yore had to have a sixth sense about torquing in those days before manufacturers gave specs and torque wrenches came on the scene.  Knowing when to quit, and what a nightmare extracting a broken one was, they rarely wrung a bolt off.  Incidentally, how does everyone feel about using ez-outs?  I don't use them, they scare me, break one off and then you're really in deep yogurt. 

[Larry Schramm]

Mechanics of yore had to have a sixth sense about torquing in those days before manufacturers gave specs and torque wrenches came on the scene.  Knowing when to quit, and what a nightmare extracting a broken one was, they rarely wrung a bolt off.  Incidentally, how does everyone feel about using ez-outs?  I don't use them, they scare me, break one off and then you're really in deep yogurt. 

 

Here is a great discussion on removing the broken stud.

 

http://forums.aaca.org/topic/32594-help-broken-stud-removal-head-stud-broken-in-block/?hl=%2Bbroken+%2Bstud+%2Bremoval

[mrpushbutton]

And now OEM manufacturers use angle and torque measurement instead of torque alone, favoring angle. I worked in the sensing and verifying/recording of Torque/Angle when this started to take hold in the US auto plants in the 1980s.

 

 

 

As for your Lycoming engine, I would do as JV suggests and look up the recommended torque for that size/pitch thread and torque to that value. Be sure to verify fine thread vs coarse.  

[Restorer32]

Buddy of mine worked at a Dodge dealership. When doing flat rate head gasket replacements he used an air wrench and made them "tight as a bull's butt", which is waterproof!

[mrpushbutton]

Buddy of mine worked at a Dodge dealership. When doing flat rate head gasket replacements he used an air wrench and made them "tight as a bull's butt", which is waterproof!

 

I know some faster engineers who would have a field day with this. 

[Restorer32]

When in doubt we just whip out the good old Engineer's Handbook and see what the recommended torque specs are for various sizes of fasteners. Best you can do. As stated above the specs provided by engine manufacturers have little to do with the actual engine and more to do with the strength of the fastener in question.

[Bud Tierney]

Does the Engineer's Book give adjustments for whether re-using existing fasteners (nuts, studs) as opposed to new ones, and/or whether fasteners tyhreads cleaned (wire brushed, whatever) and/or "oiled" or dry???

[cahartley]

Bud nailed it as per usual....... 

The difference between dry and oiled threads as it relates to torque specs is the difference between tight, broken or stripped....... 

Edited August 15, 2015 by cahartley (see edit history)

[mrpushbutton]

Suffice it to say that in the case of critical fasteners like head studs it is considered good to chase the threads with a tap and die and lubricate the threads, and replace any fasteners that have marginal threads.