turning crank shaft

[badsix]

my 356 160N crank has std. mains and rods. i believe the original engine had a catastrophic failure as it has no serial no's on it. the car only has around 80k on it so the crank could be fairly low mi. not that that makes any difference. I think i'm going to have to turn the rods down to first under question is do I need to have it rehardened I here yes and no, so i'm confused. rehardening was quite expensive
thanks Jay D.

[356JAGER]

Jay,
No rehardening needed at one under (.010").
Cheers,
Joel

[S.J.Szabo]

Mr.D:

Of course, having it magged remains a prudent choice.

Another thing to consider is that you have no assurance that any part of the engine is original to the chassis. It would not be unwise to treat every component as if it were a stranger of unknown mileage and history.

[badsix]

thanks for the reply Joel, I think that's what i.m going to do. the reason to turn the crank is that I had an engine builder put the bottom end together. then it sat for a few years wrapped with shrink wrap, although it was in a dry shop it must have sweated. the engine builder didn't lube anything other than the bearings. so a small amount of rust formed along the radius of one of the rod crank pins. this left a series of very small pits. the only reason I noticed this, was I had picked up a set of 912 rods to replace the A rods. in doing so I ran into the rust spot.
Mr.SJ, you are exactly right. who knows where some of these parts came from. about the only original engine parts that came with the car are the 3 parts of the replacement case and the crank. most everything else is new. and yes I had the crank magged when I first took the engine apart and i'm going to have it done a second time when they turn it.
thanks for your replies
Joel, Mr.SJ.
Jay D.

[badsix]

PICTURE

[Jack Staggs]

I wouldn't worry about those tiny pits for more than a few seconds. Have the surface micro polished/detailed if you like. I'd probably dress those areas with a few swipes of ultra fine crocus cloth and be done with it.
When the engine is running, those pits will fill with oil with no adverse effects. Any honest high quality crank shop will tell you the same thing.

[Don C]

The oil hole looks like that crank has already been polished or do they look like that when new?

[badsix]

yes don it been polished. I had it at a machine shop for a look see and they did the polishing and more or less said run it.

jack i'm only concerned about this as I have read that these cranks have a nasty habit of braking. I've seen pictures of broken cranks right at the spot were my problem is. could these pits cause a stress riser and promote a failure? I know if it was a s/b chevy or a big inline gmc it wouldn't bother me the least.

thanks Jay D.

[356JAGER]

Jay
A small bit of surface pitting isn't a stress riser. With these cranks it usually comes from a grinder not keeping the correct radius in the corners.

Cheers,
Joel

[gerrymc547]

I'm with Jack, sort of. I would polish the pits out, locally, with rubber wheel on a Dremmel tool, to be sure they can't become a stress-riser, then micropolish all journals. Be sure to clean all oil passages, removing the aluminum plugs for access with pipe cleaners, or similar. Many expensive overhauls have been ruined by dirty oilways in the crank.

[gerrymc547]

Joel is right. You are at greater risk from a poorly-done grinding job, than from those pits, but, they're easily removed, so, why not? Regarding magnaflux, a good idea, but, no guarantee in the case of these cranks. I've seen them break within 2000 road miles. It can tell you it WILL break, it can't tell you it will not.

[Jack Staggs]

Well, since it was mag'd prior to assembly, I don't know that I would have it tested again on a unrun engine. Good point Gerry on the cleaning of the crank passages. The blind holes can fill up with an unbelievable amount of crud.
Jay, your pix don't show enough to determine what type of crank you have. Earlier cranks are not cross drilled, and do not have blind holes and plugs. It's good that your engine was built as a "normal" originally. The lower redline substantially reduces stress and flex to the crankshaft. These problems increase exponentially the higher the rpm's. I wouldn't hesitate to use it in a customers car, unless the engine was highly modified.

[badsix]

it must be an early one as it has no plugs. it has this number stamped on it 828860. Thanks gentlemen for all the input I think its going together as is.
Jay D.

[roy mawbey]

I am not aware of the case hardened journal hardness value? Probably case hardened to a depth of 0.040" ? Anyway the hardness could be checked on hardness check machine and the Brinell ,Rockwell or Vickers value checked with the indenter. One very small impression and you have the value. Worth having that done if you just don't have the history or the crank has been reduced by a few grinds. ( If the machine is able to get the journal under the indenter I guess 5 minutes and the job is done)

Jack makes a good point that pitted area is so small.

Roy

[Meissen540]

I am not aware of the case hardened journal hardness value? Probably case hardened to a depth of 0.040" ? Anyway the hardness could be checked on hardness check machine and the Brinell ,Rockwell or Vickers value checked with the indenter. One very small impression and you have the value. Worth having that done if you just don't have the history or the crank has been reduced by a few grinds. ( If the machine is able to get the journal under the indenter I guess 5 minutes and the job is done)

Jack makes a good point that pitted area is so small.

Roy

Roy, maybe you didn't see that he says this crank is at STD, never been turned, so the nit riding has not been cut into. Thats a good recommendation at 3rd under, maybe even 2nd if something is questionable about the crank.

Jay, that amount of corrosion is nothing. Follow Jacks recommendation and go with it. It will be fine.
Tom