Crank bolt to hold damper

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I would also go ahead and get a one inch countersink to spot the crank snout with before drilling. I think your best bet is to go straight for the 13/16 drill and 7/8-14 tap size. The stock 3/4-16 drill size is 11/16, so you'll still be maintaining a 1/32 inch thread depth but with a slightly coarser pitch.
 
Have you looked at what Loctite has? They have some specific stuff for thread, shaft and keyway repair. I used the keyway stuff on a 1.8 BP Mazda where the damper went onto the crank (forged) and it repaired it. Follow the directions to the letter. The one I used only work in the absence of oxygen, so you apply the compound and assemble and let it sit 48 hours.
 
I didn’t find one deeper than stock at ARP.
I only looked under the MoPar sections. Perhaps another brand has the same size but long? IDK, lots to go through there.

For future reference, ARP has A LOT of nuts and bolts not listed in their catalog. If you call them with specs, they can find something that matches. Just an FYI.
 
They have inserts that you can use in the larger sizes

REALLY?!?! Huh! What do ya know, thanks, learned something this morning before coffee was done. Thanks.

As of now, I’m waiting on a pair of bolts. I’ll see if one of them grabs well. If not, I think I’ll drill and tap the nest size up for a nice new and fresh set of threads for full engagement with the bolt.

This May take a little while as I’m not fond of working in cold garages during winter anymore. I’m also not fairing so well with the cold winters these last couple of years. It has been difficult.
 
Going up a size is the best repair. But, I would not be looking forward to drilling and tapping the crank snout by hand. At least the motor is out of the car. Drilling straight shouldn't be too bad, but hand tapping that size and getting it straight is not going to be fall down easy in-situ. If you do try to go up a size, you probably want to use the NF thread for that size. The original used a fine thread for a reason, and I think it might be easier to tap the fine thread. if you can get the damper off, you may be able to cobble a tap guide out of PVC or something to slip over the snout and keep the tap somewhat straight. Depends on what you have available to you.
 
I myself would spend a little extra and also get a 7/8 ream to go 1/4 inch deep with before tapping and use a 1/4 longer bolt than the factory bolt. Drill overall length 3/8 deeper to bottom tap into. Having the first 1/4 inch or so of full threads on the tap guided inside of the crank itself will help tremendously on getting the tap started straight.
 
Fine threads see less strain than coarse ones so are less likely to pull out.

This bolt sees a pretty huge level of clamping force with the 135 ft lbs of torque, which is necessary to lock the damper hub to the crank, so that the hub is essentially part of the crank. That is necessary to couple the internal, torsional crank vibration energy into the damper. If the bolt is not torqued down properly, it is possible for the vibration energy to be concentrate partly in the threads rather than traveling through them to the damper hub, and that will eventually worry them out. And if fewer threads were left the last time that just concentrated more force on the remaining threads and made things worse. So that may be what has happened.

And no way I would helicoil it for these reasons; just another improper place for vibration energy to concentrate and cause future failures. Similarly, any locking compounds substituted are doomed to fail IMHO; I seriously doubt that they are intended to survive for long with the levels of vibration energy that can flow to the damper.

So any cure that does not allow you to get to the full torque on the damper bolt is cause for future failure. So I personally would move right to tapping a new hole but of minimal size increase. That is because the thinner the material that is left in the crank snout wall, the more vibrational strain it will see. For the reasons above, I personally would NOT recess the start of the threads in to the snout but start them as soon as possible. The advice to put in a recess is good for keeping them straight, but I would employ another method for starting straight threads rather than losing material anywhere.
 
Update;

I ran rethreading to the next size up (7/8) past my machinist as the first words out of my mouth. He agrees that would be best. Mostly because he and I both know this is not a low powered stock engine. A heli coil at this level isn‘t what he would do unless that is what I wanted to do, and I really don’t. As mentioned above by nm9.

So the crank will come out and he will do the job. As I’m not set up for this and have no plans (or room) to equip myself for such work. As usual, yet another delay.
But it it has to be right and at the crank is to important. Anyone ever see a balanced fly off at the track? Or street?
Uuuuuuugly......

FWIW/FYI This is my .030-360 6 pack engine. 10.7-1, 238@.050 1.6 rocker, .595 lift solid cam, 108 LSA, in @ 104, ported intake and heads, super comp headers @ 1-3/4.
4spd/4.10’s/26x10 tires.

Hoping for the best, I understand all too well about cold garages.

I’m not fairing so well these last few years in the cold. A career of outdoor work with metal, tools and midnights, I’m getting a bit worn thin.


Once the crank is done, when ever it gets taken out and done, then, I will return.......
 
This big bolt was a pain to take out. Probably because it was eating the threads inside the crank snout. Would anybody know if there is one longer than this 2-5/8 length crank bolt?

Yea, threads are destroyed inside as well, but, only as far as the bolt goes in. Perhaps tapping to the next size? Where to get the bolt?

View attachment 1715453093

Heli Coil makes crankshaft specific repair kits with deep inserts. The part number you need is 5528-12. It comes with 1 1/8 deep inserts. That's plenty enough threads. Ain't zackly cheap, but will save the crank.

https://www.amazon.com/dp/B000I1AM9U/?tag=joeychgo-20
 
I wouldn't hesitate to helicoil that thing and run heck out of it. It's arguably stronger when done correctly. Much like a cylinder sleeve.
 
agree with RRR
We have timesert here in south el monte
another great company
but nfc bolt closed
now I have to go farther to get speciality fasteners and an washers etc
 
If you lived closer, I would give you a stock 360 crank.
 
I wouldn't hesitate to helicoil that thing and run heck out of it. It's arguably stronger when done correctly. Much like a cylinder sleeve.
It's not the pullout thread strength that is the issue here RRR... it is the extra thread in the way of the vibration path to the damper that is the concern. How energy may, or may not, concentrate in the helicoil that can cause new fretting at the inner or outer threads of the helicoil, is a total unknown for a damped crank like this. I suppose you could try it, and indeed it might not be a problem, but it is not as simple a situation as it may appear. And if it is not a crank system that uses a damper, then the vibrations are not an issues.

Remember, without the damper, the crank is very much subject to breaking from the torsional vibration energy. I don't think everyone understands the high frequency torsional vibration that occurs here, and the level of energy that can be involved. It is not at all the vibration we feel from a crank imbalance; it is typically at a frequency of 6000 to 8000 cycles per second for cranks of this size range.
 
If you lived closer, I would give you a stock 360 crank.
Thanks! If the weather was warmer, shhhhhit, I’d take the drive just to say hello and break bread.

I didn’t think about this earlier, but, how would a Magnum 5.9 crank work? Balance wise. The external balance is mostly done on the outside balancer & flywheel/torque converter. If I swapped the LA balancer and flywheel over..... would that work or would a rebalancing e required
 
There's a good thought! The bobweight that I have for the 5.9L is around 2004 grams. That is quite a bit different than the LA stock bobweight that is up around 2150 grams.

But we don't know what your engine has inside for rods and pistons. Do you have a balance sheet from the build?

The LA damper and flexplate/TC are made to work with that heavier 360 LA bobweight to reach balance. The lighter 5.9L bobwieght would work with a different external weight. I just looked up the B&M flexplate for the 360 LA and, sho'nuff, it is only for the LA, up through 1992. All I can find is that the Magnum external weight is different. 5.9 Magnum to replace Older 360, flexplate?

And the stock damper weights are different too from 360 LA to 5.9L Magnum. Professional products balancer: which weight for magnum

So it very much looks like you would need to re-balance. But, if you have bobweight info from a balance sheet for the build, then you only need to balance the crank end external parts with that bobweight. I bet you can modify the external LA parts to have the lower external weight used for the Magnum; you would be taking off weight from those parts.
 
magnum LA 360 and magnum are different
IDK if 38 and 360 are the same
weight requirements are online
iMHO best to use weighted flexplate and neutral converter if starting from scratch
 
Helicoils are used extensively in the the defense industry in planes bombs & missles. A large portion of anything aluminum has helicoils in every threaded hole. One of the keys to helicoils is cleanliness so the adhesive bonds correctly. I have seen 3 inch helicoils. We ordered some that big accidentally once.

There is no vibration path through a helicoil. If the engine is balanced properly there is no vibration to transmit.
 
There is no vibration path through a helicoil. If the engine is balanced properly there is no vibration to transmit.
Please forgive me for being insistent, but unfortunately, that is wholly missing the actual vibration that is of concern. The vibration IS there. It is not the crank rotating assembly vibration that we think of with an imbalance. It is a high frequency torsional (twisting) vibration within the crank itself.

The whole point of the damper's elastomer (or fluild) is to absorb that vibration and keep the crank from reaching a high frequency resonance that can break it. The damper bolt is cranked to a high torque value to hard-couple the damper hub to the crank, and the vibrational enenrgy flows through the crank snout, the threaded connection, into the damper hub and to the elastomer. The damper ring work as a stable, constant speed rotating mass against which the elastomer or fluid is anchored so it can do its work of 'damping' these vibrations..... which is why it is called a damper!

Please read here:
Harmonic Dampeners: Why They Fail, What to Look For
https://www.klmperformance.com/coll...-balancers-crankshaft-damper-vibration-damper

There is lots of other info on this matter on the www.
 
And BTW the external balance part of the dampers made for external balance engines is a wholly separate function of the damper assembly. It has nothing to do with the vibration damping function.
 
A thought:
As I see it, the damper bolt is not the path of vibration to the damper; I see the path as:
1. interference fit between crank snout and ID of the hub
2. the hub being drawn up tight to the lower timing chain sprocket

A Helicoil, properly installed will not have a negative impact. The strength of all threads, of all nuts and bolts, has to do with the shear strength of the material they are cut into, the material of the Helicoil has a greater shear strength than the cast iron it's going into. So what's the problem?
 
last ditch effort without removing the crank (sunday night need to get to work monday morning or your in the finals and this **** happens, run what you got or go home) Use a C.A.T. damper (took a longer bolt anyway, had to go to a bolt shop and get one that was 1/4 longer) that is notoriously tight on the snout and a balancer installer (Lisle balancer puller works) It has the aformentioned threaded arbor that fully threads into the crank snout until bottomed (last 3 threads may do it) and a jackscrew nut: grease and place arbor in crank, run it down until tight, run damper over it and thread nut on. Hold arbor with 1/2 box end while tightening 1" nut. The holding power of the last 3 threads without a turning force on them may be enough to get the balancer on far enough so a retention bolt is not even needed (think Slants that had no balancer bolt from the factory, they ran the pulley on and removed the bolt or pressed them on) Mopar 2.0 didnt come with a bolt either IIRC. Run longer bolt 3 threads snug with blue locktite for peace of mind, it wont pull on threads much because the balancer has already been pressed on so its only on for retention) Heat the hub of the CAT balancer (per their instructions) and slide it on fast and use an impact on jack nut to get it on as fast and as deep as possible, then start cranking on the jack nut. If you had access to a lot of metal and a machine shop, you could make a bridge across a few other threaded bosses in the block (timing case bolts) and use that as a fixture to press on the balancer. Just thinking out loud here.....Mine looked like this and if you took the floating center off the end, it was 7/8-14 NF just like the crank ID.
GW_228675_FRNT_MAIN.jpg
 
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It's not the pullout thread strength that is the issue here RRR... it is the extra thread in the way of the vibration path to the damper that is the concern. How energy may, or may not, concentrate in the helicoil that can cause new fretting at the inner or outer threads of the helicoil, is a total unknown for a damped crank like this. I suppose you could try it, and indeed it might not be a problem, but it is not as simple a situation as it may appear. And if it is not a crank system that uses a damper, then the vibrations are not an issues.

Remember, without the damper, the crank is very much subject to breaking from the torsional vibration energy. I don't think everyone understands the high frequency torsional vibration that occurs here, and the level of energy that can be involved. It is not at all the vibration we feel from a crank imbalance; it is typically at a frequency of 6000 to 8000 cycles per second for cranks of this size range.

Are you makin that up as you go along? Pelosi needs you on the impeachment team.
 
Careful Rob, you may unleash some 8 year mechanical engineering degree stuff that no one's gonna understand.....:D
 
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