Hello all! I may have committed "light treason" by laying my crankshaft on it's side for about 6 months. I seem to recall "knowing" that this was a bad idea before doing it - but I was in the process of moving from Detroit to Charlotte and didn't have much choice (the engine is/was completely disassembled). Then I forgot about it until reading a thread the other day where a member here had a knock and found that a connecting rod bearing was worn to copper. Another member inquired about whether the crankshaft had been stored on its side for a long period of time... anyways, that woke me up and then frightened me.

My question: is a thorough plasti-gage check of the main and connecting rod bearings sufficient to see if the crankshaft has been warped? Or, is it required to be taken to a shop to be checked?

i.e. how do I ease my worry so I can sleep tonight? Thanks all!

Adam

 

I do not think your crankshaft "bent". To assuage your fears put a dial indicator on the number 4 journal and rotate the crank in the #1 and #7 journals. Or use vee blocks.

At a Motech class (underwritten by Chrysler Corp) on race engine building this question came up, specifically, "my Hemi crankshaft is tight in a spot when I rotate it." The course instructor, a prominent Mopar racer said they had found that the crank can be as much as .0060" out-of-round and there will be no adverse affects, either from a wear or power output standpoint.

I don't think I'd want to live with a .006 out crank because I'm fond of building my race motors to last several seasons, but his point was that under the dynamics of a spinning rotating assembly things will find a way to align themselves.

He had similar experiences with valve seat run out or a bent valve, but that's another topic.

I store my cranks hanging from the dampener bolt - call me guardedly superstitious.

 

So what do you with them being too long from stretching by hanging them?
Do you really think the bend from laying them on the side?
I see them taking up more room and that's it.
Dave - - - -

 

crank laid on side...truth or wives tell??? - 460 Ford Forum

https://www.ford-trucks.com/forums/3...t-storage.html

https://classicoldsmobile.com/forums...ying-down.html


Some other discussions on the topic. It, however, seems like there's no really firm answer.
However, even if it was still stored properly, I'd have a shop check over any crank before installing and using it.

 

I think that is largely an urban myth that it will take a set over time. I call BS.

At least that's what I thought until I had an Outer Limits experience. Allow me to explain:
I had an iron cylinder head that I sent out for some extensive welding. I mean on every wall of every port. When I got it back it had .150" warpage on the deck surface - like an S-shaped snake instead of flat. I thought "well this thing is now junk!" and I put it on a shelf in my basement for ten or twelve years. One day I wanted to show it to a friend to show what a foolish waste of money I spent so I pulled it out and laid a Starrett straight bar gage across it. Much to my astonishment it was completely FLAT. Warpage gone. In the ten or so years it had set on a shelf it had straightened itself out.
Now you could say the welding left a lot of internal stresses in it that caused the warpage and as time passed and it went through lots of heat cycles all those internal stresses gradually relaxed and it straightened itself out.

Maybe this crankshaft myth started this way:
Somebody could have welded up a crank - either to build up worn journals or to build a stroker crank - and ground it to finish dimension soon after welding it. Then they laid it down for an extended period. All those internal stresses from welding distorted the crank as the stressed metal relaxed into its least stressed mode. Somebody tried to use it, checked it for straightness and found it to have "bent". So they attributed it to it having been laid on its side.
BOOM
An urban legend is born.

Tell you what - I've got a bunch of old cranks. I'll measure one, hang it from the ends and check it in ten years.

 

If a crank will bend from laying flat, then with the full weight of the crank standing up shouldn't it bend the #6 rod journal (which is smaller diameter than the main journals) and pinch shut the throws over time?

 

Does a truck frame take a set over time? Let's take these analogies ad infinitum.

 

If the crank is designed to take x amount of torque, centrifugal force from rpm, heat cycles etc. For hundreds of hours and not sag/set I can't see it sitting on the shelf a certain way being an issue.

 

While I don't know if the sagging or not is true, I don't agree with this comparison at all.
When the crank is in the engine, it's supported evenly on all of its main bearings. The bearings are aligned in a very straight line. There's nowhere for it to go and the engine itself holds it straight.

If a crank is sitting on its side on the ground, the pressures/forces applied to it are going to be offset and random, due to the throws for the pistons being in all different directions. Some are going to be applying pressure upward from resting on the ground and supporting the crank's weight. Others are going to be pushing downward because they're above the crank and their weight is bearing down on it. Some off to the side. Then, there's nothing to keep it straight (like the bearings in the engine), so these forces are all applied in wonky angles without anything to counter them. The crank is heavy, so these forces are greater than they would be on other parts sitting around.

Like I said, I don't know if crank warpage is true or not, but I can see how it could happen.

 

Hi all, Thank you for the replies! They made me chuckle, and eased my mind a bit. For sure, I will thoroughly check the crank before assembly. FYI - the crankshaft was already at a shop when I had the block/head done. They put it on the lathe and lightly polished the bearing journals, but I'm not sure if they measured anything. The crankshaft was removed from a running motor, with no signs of irregular wear or problems on the bottom end. I did have, however, broken ring landings on one cylinder - which is why the motor was removed in the first place. I wanted to do a thorough tear-down and rebuild because it was a tired motor and I didn't want to find any surprises down the road.

Thanks again!

Adam

 

I was going to suggest polishing. It is more likely to be an issue than a bent crank from laying down.

 

I would think that any shop that polished the crank without checking if it was rotating straight would not be a shop I would want to patronize.

 

So, I have good news and bad news.

The GOOD news: I put the crankshaft in the block with bearing halves at position 1 and 7, and put a dial indicator on the #4 journal. It measured straight as an arrow, with no fluctuation in the dial indicator needle while rotating the crankshaft.

The BAD news: I noticed some surface rust on the bearing journals... even though the crankshaft has been coated with oil and wrapped for the 7-8 months that it has been out. You can see pictures below. Most of the journals just have light "spotting", but the #1 journal (front) has a pretty large blotch (second picture).

I'm going to call around to some local shops to see about getting it polished again. But I have a couple questions:

1. Should I be worried that polishing won't be enough?
2. Is this something I can "polish" myself? i.e. with emery cloth, or some wet sand paper I have (I have 2000, 2500, and 3000 grit already at home). My assumption is "no", but I'm curious to hear the answers from those more experienced than I.

Thanks!

 

That hurts
I would try and clean it up myself and see what happens.
They say if you can feel it with a finger nail it is no good to use that way.

Now if you "clean it" up too much it may get out of spec for that size bearing and might need to have it turned 30 under and get 30 under bearing.
They look to be mains how do the rod side look, any rust on them?
Dave ----

 

You can go only .010" under. I know some race teams who just grind that one journal undersize if they hurt one, saving the others for future oops. Make sure to mark the crank if you go that route.