Need sanity check re: base studs!

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10Pin
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Need sanity check re: base studs!

#1

Post by 10Pin »

So a guy gave me a set of 52 cases / bottom-end assembly to put together for him. They had already been matched, new bushings fitted, align-honed, etc, and bearings fitted to new pins on a trued and balanced flywheel assembly. Should be easy-peasy, so I thought...
Only issue was that the base studs had been pulled, and some of the holes have inserts in them. Ok, not ideal, but shouldn't be a big issue. Just buy some new base studs, die the course sides to get rid of the interference threading, and loctite them into the inserts. So I bought a set of Colony studs, and proceeded as noted...

During test-fitting, the studs threaded right in by hand after the massaging, but at this point I noticed the "sanity check" issue... :?: It was obvious that the course thread portion of the stud (the case side) was longer than the fine thread (base nut) side. But I didn't really think anything about it, until I realized the center studs (between the jugs) ran into one another at the common bottom of the holes! :x

So I pulled them back out, and as I looked at them, it seemed to me they were manufactured basically BACKWARDS from what I remembered! It's been a minute since I've looked at stock studs, as I normally don't pull them out unless there is a reason to... But I seem to remember the fine thread (nut) portion being the long leg, and the coarse thread (case) portion being the shorter leg. :?:
The fine thread leg on these is also BARELY long enough to go through the cylinder base and engage the nut. I s'pose it would "work", but clearly it isn't ideal!

After a little google image searching, it seems that the two most common suppliers (Colony and Eastern) manufacture their studs as described, while Vulcan Engineering seems to manufacture them as I remembered. See photos.

I'm not crazy, am I?? The two most widely distributed aftermarket manufacturers REALLY DO make their simple base studs basically BACKWARDS?! How is that possible after all this time?? And I wonder how many bikes are running around with two of the center studs sticking out an extra 1/8" due to the center interference, and with nuts hanging on by 2-3 threads?? :shock:

BTW: I'm just going to source some Grade 8 or better automotive studs of appropriate length and threading, since I can't use the interference thread with the inserts anyway... I'm just baffled that this is an issue with these supposedly "reproduction" parts!
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Andygears
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Re: Need sanity check re: base studs!

#2

Post by Andygears »

It would seem that the base tap holes in your cases have been modified, as you said. Likely they were made deeper for the helicoil tap. Why did you cut the interference from the stud thread? The studs do not need to bottom in the holes. The interference is to gain solid mounting and let the fine thread take up any retightening once the cylinders are mounted. I would use the interference studs, permanent loctite, measure the jug base, nut and washer and install each stud with two nuts to the correct height in the case for a full nut.
Be careful about accepting a lower end “all fitted” to complete the engine, you are responsible for the whole thing if you complete the build.

My opinion
Andygears
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Re: Need sanity check re: base studs!

#3

Post by 10Pin »

Andygears, thanks for the reply.
I should clarify that all the fitting items have been verified. Other than the stud issue, all is good.

As for the cases and interference thread... You do not want to use interference threads with any type of insert, particularly a Heli-Coil. Doing so will try to force the Heli-Coil lower into the tapped hole, and can even "pop" the bottom portion out of the tapped thread, causing binding and/or breakage. Or with a Time-Sert or similar solid insert, it tries to stretch the insert and can lead to distortion or breakage.
Interference threads should only be used with good, clean aluminum threads. Any kind of steel insert should use a "normal" thread fastener.

As for the depth of the holes, it honestly should not matter. A properly installed stud will seat the stud's shoulder against the surface. So long as the threaded hole is deep enough that the stud does not bottom out, a little bit deeper would not change anything.

The main issue though, is again that these very common studs are actually manufactured "backwards" from how they should be! :shock:
The short leg should be coarse and go into the case, leaving the long fine-thread leg to go through the cylinder base and have plenty of length to engage the nut.
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Re: Need sanity check re: base studs!

#4

Post by awander »

If you are loctiting the studs into the case anyway, then why not just install them so that enough stud is sticking out to work?

You can leave the unthreaded portion up high enough so that it is inside the jug flange, just low enough to leave however much thread you want to stick above the flange.
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Re: Need sanity check re: base studs!

#5

Post by RooDog »

How about these?
Just asking....

10 per Box Grade 8 Heat Treated Alloy7/16"20 x 3/4" X 7/16"-14 x 3/4" , 2 1/4" OL

https://www.kljack.com/products/av9705/ ... ced59725fa

....RooDog.....
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Re: Need sanity check re: base studs!

#6

Post by 10Pin »

RooDog - That is exactly what I ordered! :lol:
Different supplier, but same dimensions and specs.
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Re: Need sanity check re: base studs!

#7

Post by 10Pin »

Awander - I prefer a stud to properly seat, with the shoulder against the surface. Doing as you described would rely entirely on the Loctite to locate the stud in the case... Given heat cycles, vibration, etc, I am afraid it would inevitably shift and loosen up, leading to base gasket failure.

In any case, I have ordered studs exactly like the ones RooDog posted, and I'm confident they will work fine. I'd of course prefer unmolested cases, but this is far from the first time I've had to improvise.

But I'm still baffled how Colony and others can make "reproduction" studs that are so obviously wrong! :roll:
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Re: Need sanity check re: base studs!

#8

Post by Andygears »

10Pin wrote: Thu Nov 17, 2022 5:37 pm Awander - I prefer a stud to properly seat, with the shoulder against the surface. Doing as you described would rely entirely on the Loctite to locate the stud in the case... Given heat cycles, vibration, etc, I am afraid it would inevitably shift and loosen up, leading to base gasket failure.

In any case, I have ordered studs exactly like the ones RooDog posted, and I'm confident they will work fine. I'd of course prefer unmolested cases, but this is far from the first time I've had to improvise.

But I'm still baffled how Colony and others can make "reproduction" studs that are so obviously wrong! :roll:
I disagree. The thread on a straight thread stud is a “disappearing thread” version with no thread relief at the internal termination of the helix. This makes a last thread that is incomplete. Forcing the incomplete thread into a non countersunk hole jams that thread against the top of the hole and distorts it. In your case, the unthreaded portion will bottom against the helicoil with probable bending of the top steel coil in the aluminum. Furthermore, how long are the helicoils? It is not good practice to screw past the end of the helicoil, because of the burr from the tang that is used to install the helicoil will dig into the fastener and surely unscrew the helicoil when removing the stud.

I applaud your efforts to do a good job on your friends engine but I think it’s much ado about nothing. Consider the Evo long studs that have no shoulder and have reduced body diameter.

Interesting discussion,

Andygears
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Re: Need sanity check re: base studs!

#9

Post by Larry »

If you call Colony, they will be happy to discuss product issues with you.
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Re: Need sanity check re: base studs!

#10

Post by RooDog »

Larry wrote: Fri Nov 18, 2022 2:29 pm If you call Colony, they will be happy to discuss product issues with you.
Contact us at Colony

Email: info@colonymachine.com

Call: 1.800.321.3412 / 330.225.3410

Mail:
Colony
P.O. Box 126
Brunswick OH 44212

Fax: 330.225.9412
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Re: Need sanity check re: base studs!

#11

Post by tomsnosparts »

Hello.
perhaps I will post some pics later.... the NOS Harley-Davidson studs and the Colony made studs look very much the same, I cannot see any difference in the length of the coarse or fine thread portion.
Tom.
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Re: Need sanity check re: base studs!

#12

Post by RooDog »

Rule of thumb for thread engagement in soft material, such as aluminum, is double the diameter of the fastener. In this case with 7/16" stud the they should screw 7/8 of an inch into the aluminum motor case. With steel, the engagement guide line is equal to the diameter, hence a 7/16 threaded nut need only be 7/16 tall. If this is if any help to anybody.....
....RooDog.....
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Re: Need sanity check re: base studs!

#13

Post by tomsnosparts »

The park studs are the Colony reproduction and the cad studs are original NOS Harley.
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Re: Need sanity check re: base studs!

#14

Post by flatboy1950 »

You make the erroneous assumption that the studs should screw really deep into the cases.
You are wrong : there are at least 3 or 4 of the coarse threads above the case gasket face !!!
On average the inserted height of the cylinder base studs is 29 to 30 mm.
There is absolutely nothing wrong with the Colony studs !!!

Flatboy.
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Re: Need sanity check re: base studs!

#15

Post by 10Pin »

Thanks everyone for the comments.

To conclude the saga, I ended up using Vulcan studs, and they worked perfectly. Even heights, nice finish on the visible ends. I went with them only due to the appearance, as after digging through other old cases I found laying around, the comments about the studs not being threaded in so deep are correct.

Like I said, it had been a while since I messed with case studs! :lol:

The engine is now running, going through heat cycling. It started in 4 kicks (not counting prime kicks), which I'll take everyday and twice on Sunday!
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