6.2/6.5 crankshafts

[Nacla]

The forged steel crankshafts (from Peninsular Diesel) are direct replacements for engine blocks with the one-piece main seal.

Question: Has anyone ever had custom machine work done to the forged steel crank that would render it suitable for use in an older 6.2L block utilizing the two-piece main seal?

Also, I'm curious if this something Jim will be covering in his forthcoming article on 6.2L/6.5L crankshafts.

Why I'm asking: I have three engines I'm considering rebuilding. (Mine, and I have twin sons, each with their own 6.2L K3500 CC/LB trucks...1989 & 1991.)

In case it makes any difference, the first two engine blocks I have on hand are as follows:
#14022660 block with date code - "9-7-82" (Sept 7, 1982...red block?)
#14022660 block with date code - "K139" (Oct 13, 1989)

The 3rd engine block I have has different markings, which are located on the passenger-side next to the valve cover:
#14022660 block with date code - "(?) 9 2"

The first mark I cannot interpret. It looks like a raised circle with a slash running through it. Picture a clock with the minute-hand on 55, and the hour-hand on 5. (4:55) The circle is not hollowed in the center...the entire circle is raised, with the slash recessed into the surface.

The "9" is adjacent to the circle, and there is a lengthy space between the "9" and the "2" that follows. On this 3rd block, I do not see any other date code on either rear corner of the block. Maybe I'm supposed to be looking elsewhere?

-Nacla

[DmaxMaverick]

I've not heard of anyone machining the crank, and I don't know if it can or should be done. Seems like a waste of a lot of cash for the 6.2L. Some had crank issues, but most did not. If the original crank appears to be in good shape, it isn't likely to break. I would opt for the 2-piece rubber seal, vs. the rope seal (which is still included in some kits).

Your "82" block should actually be an 83. Production of the "82 red block" ended in June or July of 82.

I'm not familiar with your weird date code. Good luck with that.

[Nacla]

Thanks for the input.

Thought I'd read, somewhere, a statement about machining this crank to work with a two-piece main seal. Maybe not.

I imagine you're correct about the expense of a forged steel crank PLUS the cost of machine work. Was thinking about economical DD engines, and the best durability - not more power. My friend is leaving Alaska, and gave me the three engines.

One of the three he gave to me (date code: K139) has a broken crank, outside the block, right where the harmonic balancer mounts. He gave me a used crank for it, which a local machine shop had turned down -.010" on both the main and rod journals. Using that ground crank has me a bit spooked.

The other two blocks still have the original cranks installed, but I'm unsure of their condition, hence my thought of biting the bullet and springing for the forged steel cranks Peninsular sells.

I've read all TDP articles I could find, on the crankshaft topic. There are certainly a lot of horror stories about crank failures, posted here in the forum.

-Nacla

[More Power]

The forged steel crankshafts (from Peninsular Diesel) are direct replacements for engine blocks with the one-piece main seal.

Question: Has anyone ever had custom machine work done to the forged steel crank that would render it suitable for use in an older 6.2L block utilizing the two-piece main seal?

Also, I'm curious if this something Jim will be covering in his forthcoming article on 6.2L/6.5L crankshafts.
-Nacla

I have spoken to a member who has already or will be machining a 2-piece rear main seal block to accept the one-piece rear main seal crank. I haven't spoken to him in a few months, so I don't know what the current status is. Jim

[AKMark]

Nacla,

If you need machine work up here, Port's Machine Shop helped me rebuild a few 6.2's in the past and have done lots of work on gassers for buddies of mine.

They can get parts a pretty reasonable prices as well.

I've experienced crank failure, wouldn't go with one that has been ground, ever. (My preference)

Ports can check the cranks to ensure they are good prior to install. When I rebuilt mine, I gave them two cranks and two cams and they evaluated them. Glad I did, as one of my cranks was slightly warped already.

[Nacla]

Jim,

Thanks for clarifying that it's the two-piece main seal block that someone is modifying to fit the forged steel crankshaft - and not the crank being machined to fit the block. I hope we'll hear about it, here.

Am eagerly looking forward to the "What's Coming" articles on the 6.2/6.5L cranks, and the further 6.5L rebuild info.

-Nacla

[Nacla]

AKMark,

Thanks for pointing me in the right direction!

Yours was one of the crankshaft horror stories I was referring to. I don't think I'll use the crank that's been ground (-010") on anything that I might drive out of town.

Living where we do, you know exactly what it would be like if something catastrophic were to happen several hundred miles from home, out in the middle of nowhere. :eek:

-Nacla

[AKMark]

Folks don't understand that there's not much for 300 miles no matter which way you go out of this town.

Breakdowns suck up here.

[More Power]

Jim,

Thanks for clarifying that it's the two-piece main seal block that someone is modifying to fit the forged steel crankshaft - and not the crank being machined to fit the block. I hope we'll hear about it, here.

Am eagerly looking forward to the "What's Coming" articles on the 6.2/6.5L cranks, and the further 6.5L rebuild info.

-Nacla

Yes, that's what I remember discussing with him - modifying a 2-piece rear main seal block to accept the newer crank.

Jim

[Mikey von]

The crank in my 6.2 is a NOS crank that was machined to a 6.2L 2 piece block. I did not do it, but bought it that way.

[Nacla]

The crank in my 6.2 is a NOS crank that was machined to a 6.2L 2 piece block. I did not do it, but bought it that way.

Mikey Von,

I'm not certain what you mean by a "NOS crank." (I searched TDP list of acronyms, and it's not listed.) Are you referring to the factory nodular iron crank model with the one-piece main seal?

If it's a factory crank, or even an aftermarket SCAT crank (which are cast; not forged), why would anyone have gone to the trouble to machine it to fit the older two-piece main seal block? (ie: Couldn't find any good older cranks? Couldn't find any good newer blocks? Owned their own machine shop?)

What I was pondering over, when I started this thread, was a way to upgrade to forged steel crank reliability without waiting around, hoping to find a good "599" or later block. (IIRC, that's the year GM began producing exclusively one-piece main seal blocks for 6.2/6.5L.)

The supply of usable 599 (and 929 and 141) blocks appears to be drying up. There's still a number of older "660" blocks out there, and if these two-piece main seal blocks could be machined to fit Peninsular Diesel's forged crank, without too much expense, it might be a worthwhile endeavor.

But...these are merely my uneducated ponderings.

-Nacla

[trbankii]

NOS - New Old Stock

[Robyn]

Just gotta love all the acronyms and slang eh :D


NOS parts are a nice find when you need them.


MGW

[Nacla]

The crank in my 6.2 is a NOS crank that was machined to a 6.2L 2 piece block. I did not do it, but bought it that way.

Mikey Von, are you having any oil leaking issues from your rear main seal?

I searched around until I found the write-up, by the builder of your engine. IIRC he expressed some uncertainty as to whether or not your machined crank's reduced-OD oil slinger ring would result in main seal leakage.

Just curious how it's been working out for you.

-Nacla

[Nacla]

I've not heard of anyone machining the crank, and I don't know if it can or should be done. Seems like a waste of a lot of cash for the 6.2L. Some had crank issues, but most did not. If the original crank appears to be in good shape, it isn't likely to break. I would opt for the 2-piece rubber seal, vs. the rope seal (which is still included in some kits).

Your "82" block should actually be an 83. Production of the "82 red block" ended in June or July of 82.

I'm not familiar with your weird date code. Good luck with that.

DmaxMaverick,

Thanks for the clarification on the "red block."

I was thinking I'd read (a few years back) where somebody machined a one-piece crank to make it work in a two-piece 660 block. FWIW, I found the write-up. It's a lengthy writeup at another website's forum (ck5) by a member calling himself MaxPF.

Seems this guy has some machining skills, and used his buddies machine shop to grind the rear of the crank, behind the rear of the main bearing, out toward the end.

MaxPF's concern was that there wasn't enough material (crank diameter) where the oil slinger ring is located to replicate the ring on the two-piece seal cranks. His concern was possible rear main seal leakage, as a result.

I believe this was the engine that TDP member, Mikey Von, bought.

Sounds like any good machinist could do the same. However, You're probably right, it does seem likely it would take "a lot of cash" if you don't have the skills to DIY.

-Nacla

[Robyn]

As much as the one piece seal is a nice idea, I have never had a rear main seal leak issue on any 6.2 engine.

Use the two piece seal crank with the neoprene (Rubber) seals

Add a tiny dab of hitack to the seal ends and be sure to place a little sealant at the area between the cap and block right adjacent to the seal at the rear to prevent seepage.

Machining a one piece crank to fit a two piece block is a marginal idea me thinks.

As Maverick mentioned, the 6.2 cranks rarely gave issue.

If its in good shape, use it.

Miisy

[Nacla]

As much as the one piece seal is a nice idea, I have never had a rear main seal leak issue on any 6.2 engine.

Use the two piece seal crank with the neoprene (Rubber) seals

Add a tiny dab of hitack to the seal ends and be sure to place a little sealant at the area between the cap and block right adjacent to the seal at the rear to prevent seepage.

Machining a one piece crank to fit a two piece block is a marginal idea me thinks.

As Maverick mentioned, the 6.2 cranks rarely gave issue.

If its in good shape, use it.

Miisy

Thanks, Robyn.

I've been taking notes, here, reading for the past few weeks.

Assuming one has a good used 6.2 crank, what would YOU do to prevent crank failure in an engine YOU were building?

IIRC, here are things I should consider doing to minimize crank fatigue:

1) - Balance the crank (with new harmonic balancer)
2) - Have rod lengths equalized
3) - Static balance of rods/pistons
4) - POP test injectors & adjust each to within 25psi of each other
5) - Confirm flywheel is in good shape
6) - Use a new harmonic balancer
7) - Maybe use a gear drive instead of a timing chain

Did I miss anything that YOU might do?

Anything I've listed, above, that you think unnecessary?

Off-topic curiosity: What exactly is your "DaHoooley" anyway? Have enjoyed your posts. Just wondering.

-Nacla

[Robyn]

A good harmonic balancer is a must have.

Balancing the rotating assembly is a real plus.

One much overlooked item is getting the injectors rebuilt with their pop pressures as close to the same as possible.

This assures equal cylinder to cylinder timing, and helps keep torsional vibrations to a minimum.

Power pulses that are out of sink really can stress the crank.


Missy

[Mikey von]

Mikey Von, are you having any oil leaking issues from your rear main seal?

I searched around until I found the write-up, by the builder of your engine. IIRC he expressed some uncertainty as to whether or not your machined crank's reduced-OD oil slinger ring would result in main seal leakage.

Just curious how it's been working out for you.

-Nacla


DmaxMaverick,

Thanks for the clarification on the "red block."

I was thinking I'd read (a few years back) where somebody machined a one-piece crank to make it work in a two-piece 660 block. FWIW, I found the write-up. It's a lengthy writeup at another website's forum (ck5) by a member calling himself MaxPF.

Seems this guy has some machining skills, and used his buddies machine shop to grind the rear of the crank, behind the rear of the main bearing, out toward the end.

MaxPF's concern was that there wasn't enough material (crank diameter) where the oil slinger ring is located to replicate the ring on the two-piece seal cranks. His concern was possible rear main seal leakage, as a result.

I believe this was the engine that TDP member, Mikey Von, bought.

Sounds like any good machinist could do the same. However, You're probably right, it does seem likely it would take "a lot of cash" if you don't have the skills to DIY.

-Nacla

Yes, I purchased MaxPF's project build. I followed MaxPF on CK5, but he actually listed my engine here.

I have had no issues with the rear main seal.