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MLS gaskets were the best thing ever come up with for the old bikes, but that doesn't change the stud used, it enhances the intended design. You're kinda over reacting to the bit in question here.
I'm in the auto building industry, several decades now. Fasteners are very serious business and designed for specific application and specifications. Elongation and deliberate stretch are very real going back to early aircraft engine designs. One shot fasteners are the thing on most everything for decades now. Isn't myth or internet repeated fairy tales. Why most serious engine hardware is replaced once used today, the base properties changed when torqued and ran through heat cycles. It's deliberate metallurgy and physics not redneck hearsay. Idea was build in some give to help not chew the old garlock gaskets up through the heat cycles, radial aircraft engines used similar tech year back with about as much success not leaking.
Owners and backyard mechanics usually screwed that pooch over tightening slathering on gasket sealers allowing the gskets to squish out on the corners under the stud holes.
Nobody said **** about shovel cylinders by the way, we're chatting about cast alum heads and rocker boxes not cast iron, huge expansion factor difference. Shovel head bolts and base studs are as grunt proof you get, why you see rounded base nuts and head bolts or pulled thread bosses in the heads or the cases, they don't stretch and I've never seen one break.
Teslas and shovelheads, could two things be any more different to compare to? Im not disputing modern bolts vs old and measuring stretch or torque angle vs final torque but that's not what we're talking about. Getting back to the comment John made about stretchy studs is where I call BS because all studs stretch, all bolts and screws stretch and Harley was not ahead of its time when they supposedly created a unique rocker box stud that expanded and shrunk with the engine - they all do that anyway whether an engineer likes it or not.
And just out of curiosity how did you arrive at the .100" growth measurement?
Teslas and shovelheads, could two things be any more different to compare to? Im not disputing modern bolts vs old and measuring stretch or torque angle vs final torque but that's not what we're talking about. Getting back to the comment John made about stretchy studs is where I call BS because all studs stretch, all bolts and screws stretch and Harley was not ahead of its time when they supposedly created a unique rocker box stud that expanded and shrunk with the engine - they all do that anyway whether an engineer likes it or not.
And just out of curiosity how did you arrive at the .100" growth measurement?
Not going to split hairs over this but John isn't wrong about the box studs.
Watched a couple different build engines bolted to a static test stand and run with dial indicators on each head through several heat cycles, low was .065" high was a hair over .100" growth at running temps. Chopper shop/builder in KC was geeky about his stuff but very interesting to hang out with when the game was on.
every job a fixing is needed to do, will have a 'perfect for job' form, thread, material for the fixing needed,
if ya look at old Harleys like Knucks, 45's pans etc, everything used with a thread, they used the best thread needed for its use, so fine, coarse,special pitch, cycle threads etc even bsf,whitworth were all used (well, don't think Harley used Whitworth but ya get wot i mean) if it were the 'right' item for the job.they used it..
all fixings have an optimum use, torque grade & material, & in the day, the right/best thread was used & to hell with the cost.
now its a compramise, penny pinching use of metric is easy & works, saves cash, but not the best from an engineers view,
older bikes were over engineered, and now we know to use fewer threads & forms as modern specs are not as high as they were,
and as so some bolts, studs nuts etc are at their limits when in use, so need replacing as 'Service Items' more often than on older motors where the correct bolts were used in the first place plus less stress was put through them,..
I'm no engineer but I can understand why the shovelhead factory studs are "more stretchy", than a full diameter stud. I'm sure Harley didn't do it to save weight.
Got the motor and transmission out and haven't found anything really F'd up that would kill the project. Just greasy as hell. Going to get the frame stripped and start the cleaning process so I can sand blast the welds and check them and get it ready for the powder coater. The big question is, should I go back to stock rocker studs or stick with what I have?
I got the transmission cleaned but I'm feeling roughness when I turn the mainshaft like there is a bad bearing. On the list. I can have my machinist buddy check to see if the rocker boxes are flat and mill them if needed. Thanks for the tip.
Last edited by AlCherry; Nov 10, 2022 at 02:14 PM.
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