Crank Only the Rod Journals Cut

[72DMag]

Dropped off a crankshaft from a 2000 5.9 magnum to get cut. Machinist said he was only going to cut the rod journals on the crank and just polish the mains. Is there any issues with this? Never heard of this being done before. Usually its cut 10 on both.

 

[RustyRatRod]

Why would the mains be ground if they don't need it? It's not uncommon. Don't look a gift horse in the mouth.

 

[72DMag]

@RustyRatRod That's true but honestly I guess I have a good machine shop because prior places in the past I have taken spotless cranks for polishing and they insisted to cut both rod and main journals.

It also seemed odd to run a standard main bearing but a 10 over rod bearing. I can't think of a reason why that would hurt but never built a motor with a crank like that before.

 

[RustyRatRod]

@RustyRatRod That's true but honestly I guess I have a good machine shop because prior places in the past I have taken spotless cranks for polishing and they insisted to cut both rod and main journals.

It also seemed odd to run a standard main bearing but a 10 over rod bearing. I can't think of a reason why that would hurt but never built a motor with a crank like that before.

They come like that everyday in the aftermarket when you get a crank kit. There's no guarantee what you'll get. No reason whatsoever the rod and main journals have to be the same under size. You're all good. I wouldn't worry about a thing.

 

[toolmanmike]

If you ask for a .010/.010 cut you will probably get that. I am impressed the guy checked it and is just doing what is necessary to do the job right.

 

[brian6pac]

I had to talk my machinist in to just turn 1 rod journal that spun a bearing, well it was actually 2 rods but 1 journal .020 all the rest were good

 

[72DMag]

@toolmanmike Me too!! Thanks Guys

 

[moper]

No problem - shop is looking out for you.

 

[MoparMike1974]

Not a thing wrong with it, only cut what is needed. Some engines came from the factory undersize like this. My 340 has std mains and 10 under rods (or vice versa, cant remember) from the factory.
"Maltese Cross" and non standard sizes from factory?

 

[Brooks James]

My slant years ago came from ma mopar with the rod journals 10 under no problems

 

[Demonracer]

My 408 crank is cut .010 mains & std rods, the 416 crank is .010 rods & std mains. Put it together & drive it like you stole it!

 

[MOPAROFFICIAL]

Dropped off a crankshaft from a 2000 5.9 magnum to get cut. Machinist said he was only going to cut the rod journals on the crank and just polish the mains. Is there any issues with this? Never heard of this being done before. Usually its cut 10 on both.

Sounds like a good plan.
It does not matter if you cut both main & rod or just one main or rod more or less than the others as long as it's balanced.

 

[oldkimmer]

Sounds like a good plan.
It does not matter if you cut both main & rod or just one main or rod more or less than the others as long as it's balanced.

My ocd would get the best of me. It would have to be all rods the same size. All the mains the same size. Not that it would matter like u say. Kim

 

[65 Cuda 340]

I once let a machine shop polish a 383 crank and they polished so much off that I ended up having to grind the crank 10/10. Had a few other issues with them, too (piston installed backwards, reconditioned rod that was bent, etc). Sad thing was that it was a well-known shop with many racing successes. Long out of business now (this was several decades ago).

 

[Dartswinger70]

I've seen it before, I just sent one out has the mains .010 under and the rods .020 under. Only issue I see is if someone assumes they are both .010 under and orders the wrong bearings. I would mic the crank to determine bearing size, and usually it is marked somewhere on the crank. I suppose what really matters is the oil\
clearance in the end. how the plasti gauge checks out.

 

[MOPAROFFICIAL]

I once let a machine shop polish a 383 crank and they polished so much off that I ended up having to grind the crank 10/10. Had a few other issues with them, too (piston installed backwards, reconditioned rod that was bent, etc). Sad thing was that it was a well-known shop with many racing successes. Long out of business now (this was several decades ago).

The crank polish story, I have one too.
It was hard to watch the owner do it wrong right before my eyes... I tried to tell him to stop on one journal...and he leaned on it instead. The belt just V 'd over the crank... you could feel .005 diff across the journal.
I don't know what in the hell he was thinking or what anyone is thinking when they do that to be honest. All you have to do is shine it and move on you don't have to sit there going back and forth...and you don't lean on it only as much as that initial shine takes to show itself. I had him grind the rods to .020 from the perfect .010 they were at. They've also used to the wrong stone to finish hone, had to take it back.
I've had another shop do an inspection of a build that kept scuffing no.5...they had just done all the machining prior to assembly...but treated it like 200k rebuild and knicked the crank in 2 places disassembling it...a fresh perfect 340 crank. Another shop... had them do a 45 touch on the seats of a 7 angle serdi job previously done... mfkrs put the heads in a shot blast machine...wasted the valve job , then touched the 45 and gave them back to me. The guy who cleans everything was a 'mopar guy' and wanted to make sure they weren't cracked and clean like from the factory...straight playing around with my stuff. Fkn idiots. So I ended up with art on a hill of what used to be crisp angles. Had to touch them all up myself later on once I got the seat grinder. They also like cutting guides for seals to .500 on everything that would really use a .530... they dont do what I expect or what most people would...then they go n do extra in light of complaining they left things undone previously..and do what you dont want, like .500 seal cuts...when I already had the cutter and seals bought to do it myself.

Anybody out there with a machine shop reading this .. .all it takes is a phone call, that's it. ...Ask , listen, explain the plan...
Going on autopilot is very prevalent.

 

[Dartswinger70]

They say its difficult to find a good machine shop these days. i took my crank to one recently ,he "sent out" my crank to another shop in another town for the crank polish job. It looked good but I havent checked it yet. I will mic it and plasti gauge it. Looks can be deceiving

 

[65 Cuda 340]

Had a shop balance a Packard V8 rotating assembly - forged pistons, stock reconditioned rods and a very rare Packard forged crank. Didn't clean the crank myself, figured they could do it. Left them with two sets of rod bearings in case the crank needed grinding. Went to pick it all up when "done." Guy said, well, the crank really probably should be ground. Really? Wasn't that why I left you with two sets of bearings? But worse, he said you have some pitting in the rear seal area. Huh? You couldn't call me and tell me before you balanced it? I had a perfectly good reground cast crank; could have balanced the assembly with that crank instead. Now I've got a forged crank I can't use without it being welded up and re-machined in the rear seal area, and a cast crank that needs to be balanced for the light forged pistons. Got so disgusted, I've just let it all sit for a couple of years.

 

[72DMag]

Thanks everyone for all the info and the stories.

lol

 

[MOPAROFFICIAL]

They say its difficult to find a good machine shop these days. i took my crank to one recently ,he "sent out" my crank to another shop in another town for the crank polish job. It looked good but I havent checked it yet. I will mic it and plasti gauge it. Looks can be deceiving

If it looks good... It's at the very least still round!!

 

[MOPAROFFICIAL]

My ocd would get the best of me. It would have to be all rods the same size. All the mains the same size. Not that it would matter like u say. Kim

I suffer too. Lol

 

[MOPAROFFICIAL]

Had a shop balance a Packard V8 rotating assembly - forged pistons, stock reconditioned rods and a very rare Packard forged crank. Didn't clean the crank myself, figured they could do it. Left them with two sets of rod bearings in case the crank needed grinding. Went to pick it all up when "done." Guy said, well, the crank really probably should be ground. Really? Wasn't that why I left you with two sets of bearings? But worse, he said you have some pitting in the rear seal area. Huh? You couldn't call me and tell me before you balanced it? I had a perfectly good reground cast crank; could have balanced the assembly with that crank instead. Now I've got a forged crank I can't use without it being welded up and re-machined in the rear seal area, and a cast crank that needs to be balanced for the light forged pistons. Got so disgusted, I've just let it all sit for a couple of years.

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There was a member here on this site who happened to be local and he had a rear main seal leak with the 225 he had in his Valiant wagon. So he brought it over for me to change the rear main seal and pan gaskets. Upon taking it apart I saw the cranks seal surface was pitted and had no grooves...they were polished off or something. He wasn't very happy about it.
I sold him either a core crank or motor all together to be rebuilt and installed in his car. Probably cost him 2,200 in the end.
12 for the motor and another grand for pulling the first one apart , yankin the motor out core.. and then reinstalling the new one.
I remember it sitting in my driveway too, for a week or so iirr. He was impatient being it was his only car, and it had been sitting in his parents driveway at that point before I accepted the gig. Dunno what happened with that dude or car. Lol so many stories.