Crank bolt to hold damper

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JBurch said:
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?
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Good thought now that you mention it, so thanks. I'd see the path as through both your number 2 above and the threads; any clamping force of the damper hub to the crank spocket comes only from the force generated in the threads and so both have to be in the vibration the path. I'd guess that you number 1 is not much of a path for vibration; it would eventually work loose if any vibration was present and is much lower than the other forces anyway.

And yes on the helicoil shear strength in steel and cast. Separate issue from vibration though. That is my concern. I've never done it so it may work... or may not.

RustyRatRod said:
Are you makin that up as you go along? Pelosi needs you on the impeachment team.
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LOL... well the crank vibration info is all over the www Rob. Look it up.
 
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nm9stheham said:
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.
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No BOB weight info. I have the wholething balanced and running before. I took it out to check health in general after sitting for 5 years, 1 year without heads on top. It took some easy work with a scotch bright green pad, but cleaned up real quick! So, that being said, I have the balancer and flywheel already balanced to the assembly.

The key, or problem, is the crank itself. Is there a difference between the LA 360 crank and the .00 - 5.9 Magnum crank in terms of balance of itself only.

Wyrmrider said:
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
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This is a LA 360 with smoothed OE rods & KB-107-.030 slugs already balanced with a LA 360 flywheel (833 4spd manual trans) and OE LA 360 damper.

The balance wold be different due to pistons wight on the 5.2 vs 5.9 just like the LA 318 vs 360.
 
360 Magnum cranks are dimensionally interchangeable with LA 360 cranks. Direct swap. The engines do have different balance requirements, but I do not know if all that balance was in the flex plate and harmonic balancer or also in the holes drilled in the crank counterweights themselves.
I do know that Mopar Performance offered a Magnum based short block that was balanced like an LA engine, so it is easy to do if you know the bob weight. Not neutral balanced, external balanced. But, I forget if its 360 or 340 external balance.
Also, yesterday I dropped off a crank at a local crankshaft grinding shop. Not a builder, an actual crankshaft grinder. While there I asked about this thread situation and they said they would replace the crankshaft with a new or used core part. They would not try repairing those threads due to cost. Basically cores are too cheap to deal with this, so they have no process other than replacement.
I think your plan for next size rethreading is still best plan, unless rebalancing a replacement is an option for you.
 
I shoulda looked at this sooner... sorry RF360. Crankshaft Supply lists the same crank PN for both 360LA and 5.9L Magnum, from start to finish of all of the 360/5.9L production years.

Now whether the crank finishwork for balance was identical for all, IDK. But the main source that I know of for the lighter external weights on the 5.9L is due to the lighter pistons, and slightly lighter rods, which reduces the nominal production bobweight from around 2150 for the 360LA to around 2004 for the 5.9L Magnum. (From my collected data....) So my presumption is that the actual crank balance is uniform for all the 360/5.9L cranks.

It would be worthwhile to dig out the machinist's data books for cranks to see what that says. I found an online copy of the AERA book from 2006 and it shows the same 2 casting numbers running through all years of 360LA and 5.9L Magnum production: 3418640 & 4027169. There are 2 other casting numbers that show up for the LA and LA roller years only: 3418840 & 3418995. I can't spot any dimension differences. (Perhaps these 2 are for manual trans?)

http://www.guiaautomotrizcr.com/images/Manueal%20de%20Cig%FCe%F1al.pdf
 
That casting number 4027169 is the same one found in the later model LA 360 I am tinkering with now, so we know it's not a Magnum specific casting, backing up the listing nm9stheham found. Of course, that's me assuming this casting number was not swapped into this LA engine before I got it.
 
This is the crank that cam in the engine which was taken out of the car by myself from the original owner whom babied the heck out of the car with records of the car.

This is the crank that came with the engine.
 
Well, if Crankshaft Supply is selling the same cranks for both LA360's and 5.9L Magnum's that is a good sign that they are the same, including balance of the crankshaft by itself.

Of course, the same casting could have been processed a bit differently at the crank balance station when they changed to the 5.9L's....but I am tending to thank that is not the case. Interestingly, the A/LA318 and 5.2L Magnum cranks are the same throughout the years for balance from all I have been able to gather. IMHO, it says that keeping the cranks consistent was a desired thing for Mopar.

RF, since you had this rotating assembly balanced before, we have to assume that the crank was 'touched' in that process. It is possible that they just modified the external parts, but it is generally easier for them to drill the crank counterweights.

You could take a new crank, the external parts, and one piston/rod assembly to the shop and have the new crank balanced to that. I'm working on the assumption that all 8 of the piston/rod assemblies were balanced to each other; if you paid $300-500 for the balance job, then that 99.99% is certain to have been done. With that being the case, the 1 piston/rod assembly that you take to the shop could be used to figure out the bobweight and use that in the re-balance process of the new crank.

And if you go back to the same shop, they might just have the old bobweight data somewhere.
 
NM9, I’m just going to have the old crank worked on in the future. As of right now, I have 4 engines in various states of build which has my garage completely jamming me up. I will have no room until I get job #1 done and out of the way. Then I can shuffle the other two around (the 6 pack I’m on and a 340) and start making progress. The 3rd I think I’ll wait on a bit so I can keep clear some garage space and clear the head some.

But yes your right. The crank was cut and balanced as an external assembly. I’ll get the cranked tapped for cheap rather than any other move thoughtfully suggested by everyone. As mentioned, there will be no balance issues since the crank bolt will be on the center of the spinning mass.
 
Man, that is a traffic jam RF. I am just limited due all the crap in the main garage LOL. Getting to start on assembling my latest Opel just now.

And yes, no balance effect whatsoever with the new crank bolt. It sounds like you have a good plan there.
 
Thanks, again just figured I’d run it past the crew and see what’s what. Never hurts to ask when your head and garage are full ****.

I still have to dig out 2 more 340 blocks for sonic checking and hope to get into those soon. 1 for 372-W2, a W5 @ a unknown displacement. We will see what the block says... I’d like to make it as big as I can. While a huge size will out strip the head capacity, it’ll also peak at a low rpm which is less stress and the cubes will leave room for a better head like the Victor, also, I have a MP circle track crank for 352 cubes on a 4.03 bore. But what 340 has that? LOL, yeaaaaaaa, no race blocks here. Custom slugs on what ever the next best block says.
A big bore 340 could give me 360 cubes in a odd manor.

Im chock full....

Let’s not talk about the 2 - 400 Blocks yet OK?!?!
:lol:
 
So when you get the snout threads sorted and are ready to install the damper are you going to draw the damper on with the bolt and washer or use a specific tool or something akin to a threaded stud or? that threads all the way into the snout and then draw the damper into position with a nut and washers?
 
I have always used a rubber mallet to seat the damper.
 
rumblefish360 said:
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?

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Did you end up getting this one resolved? I finally ran a tap through mine and was fortunate enough that it turned out well, but then started wondering which way you went on yours. Just curious.
 
@Bobzilla , just a few days ago I had the crank heli coiled. The bolt threads in fine enough. I haven’t had the time to get any further than reassembling the short block and installing the heads with 2 weak cam timing checking springs. As so to degree the cam in.

It’ll be a couple of days before I degree the cam in. I’m about clear to do the work. I’ve been catching a drubbing on other home front issues that of course, come first. Toys second, always.
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In the mean time, while I was waiting for this to get done, and slammed together a 340, got interrupted with the crank above and then returned to the 340, mounted it up, broke in the cam and I’m about ready to install the engine in the rat box Duster.
10.25-1, stock Edelbrock top end w/750 AFB carb.
I had Comp move the C line to 108 from 110.
96461CE3-99B4-428C-9098-64CACAC1511F.jpeg
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The Ga. Mud Bug.

This thing is a scream. My son in law and I had a low deck B 400 in it with bolt one and stuff with 4.88’s killing it up on the turnpike for a summer.

F98245E7-3901-40AD-B43B-10E03B2D5830.jpeg
 
Glad it worked out. HeliCoil should hold nicely, I would think.
That 340 should be a solid little powerhouse too.
I am in the same boat with delays. I was hoping to be back on the road in early May but the Covid-19 crap delayed me more. Still hoping for this year. Mine is 75 Dart Sport that has been off the road about 6 years after it wiped a cam lobe. I was running a mild 400 low deck with hydraulic cam and 4.30 rear gears and drag radials. Too many freeway miles with 4.30 gears likely contributed to my cam lobe failure.
 
All the machinists here are behind if there even open. Good luck with getting your ride back up and running quickly.

I think that 340 will be OK. Once (or read the word “IF”) I can get to lightening the car up, it’ll be a good street runner. Being the heads are stock (and a bit worn out after 26 years....) I think it’s in the 430 HP area. I would like to get the car under 3K myself.

The Duster was a /6-904 that I got as a shell only. Zero interior. Perfect for the tablet build. NO nonsense or fan fair street runner. Manual everything, no A/C, 4 wheel drums have to be addressed to discs.

Heli coil shot

4B982EE6-949F-4DD1-B9D9-7C4D3ADEBC6B.jpeg
 
rumblefish360 said:
@Bobzilla , just a few days ago I had the crank heli coiled. The bolt threads in fine enough. I haven’t had the time to get any further than reassembling the short block and installing the heads with 2 weak cam timing checking springs. As so to degree the cam in.

It’ll be a couple of days before I degree the cam in. I’m about clear to do the work. I’ve been catching a drubbing on other home front issues that of course, come first. Toys second, always.
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Rob, are those Hughes rockers? Thanks. Kim
 
Yes, for the big mouth heads in a 1.6 ratio.
I still yet have to mess with them. I can tell you right now that the pack of shims Hughes sends along with them are not going to be enough to get it in the ball park.

Basic engine specs;
.030-360 @ 10.5-1
Ported 6 pack intake
Big Mouth heads
Hooker Super Comps
Backed up a 4spd & a 8-3/4 w/4.10’s on a 26-1/2 tire.

Cam card below;

D9290010-EAE9-4968-BFD2-9CD63CF25F08.jpeg
 
I asked because they look like the set I have. Very nice rockers. Are the shafts grooved? I only got rockers, nothing else. Nice build. Should be fun. Kim
 
Ummm, I think they are... LMAO!
I’m pretty sure they are. Like 99.9999% sure.
I’d say yes. I’ll look at them tomorrow. I’m at work now.
 
Glad you got it fixed. I knew the heli coil would work.
 
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