Found this on a rod journal :



It's otherwise nice and within specs.
Should I buy a new one ?

 

I think you can get that polished out. Looks like a rod bolt hit it.

 

Even if it's been turned before, you can safely turn most cranks down to .050 under. As posted above, it looks like a rod bolt hit it during assembly or disassembly. If you're on a budget, you might get it polished out but judging by the small lines in the journals, I'd recommend you have it turned down by a competent crankshaft grinder. Save yourself some money, have this one turned and spend the rest on other parts. Or...pick up a stroker kit and go to town!

 

I would take it down and have it checked out. Hard to tell from a picture how bad that is. Looks like that crank could use a good polish anyway.

 

I'd be concerned about the cause of the wear patterns and apparent discoloration around the journal. What did the bearings look like?

Be aware that if the surfaces were originally hardened, you'll need to have that process redone in the event of turning or possibly after any aggressive polishing.

 

I agree it's a trip to the shop; I don't think it's going to polish out; you can always take some crocus cloth, a little solvent and cord and try it a bit.

I share the concern regarding the wear patterns as well.

I'd have to think twice about an .050 grind; I think .030 is fine but at .050 I'd probably consider an aftermarket crank given how cheap they are.

 

If you can catch a fingernail on the throws by dragging it across the surface, then its a good back alley guide to get a new crank or have yours ground. To the best of my knowledge there are no .050 bearings and you wouldn`t want one that size any way at least not a modern higher winding V8.......

 

Thats way to deep for polishing, it will have to be ground. .030
is what a machine shop will do and you would not even really
want that, if it will go .010 thats good
.020. all you would ever really want to go. . I would say
.010 might clean it up, but it will be close, it may have to go .020
no more the .020. truth is with chinese steel cranks so cheap if
.010 wont do it just get yourself a new crank. thick bearings
are just not the way to go.

 

Dunno ... new cranks may be $$$ in France ... labor may be $$$ too ... dunno?

Notice there are a few grooves in addition to the rod bolt dings... also the oil holes need chamfering.

Suggest take it to a good professional shop & have all journals turned down, the oil holes chamfered and all journals polished.

FYI ... IC so right ... NO off the shelf 0.050" R or M bearings for sbc. If 350 rod journals get REALLY really bad they can be turned to 0.100" under and run 283/327 rods. During disassembly/assembly ... Put some rubber tubing over the rod bolts to prevent rbolt dings. During assembly, make certain journal is at absolute bottom dead center for EACH cylinder you're installing a piston in ... that'll help prevent rod dings.

BTW ... can't be certain but that looks more like a cast crank rather than forged.

 

Did not even look at where you were from, you may need to
grind it.

 

Jackson how much lift would be a rough guess, that a 4 eybow
dished 350 piston with a short duration cam can handle. with
maybe .038 to .041 piston to head clearnce.

 

Rough guess ... .525 - .600 ... rough guess ... do check it w/ clay.

 

I'm helping someone on the forum. he has a dial indicator and
bridge on its way to him, I want to make sure how far the
pistons are in the hole 1,7,2,8 he has 68cc heads, dished
pistons, and has been running 9.2cc voluum gasket. I"m trying
to get him into a 3.2cc voluum gasket, changing pistons is out,
I told him how to do the clay thing, but he can't seem to get me anything on valve clearance. Thanks

 

In the alley behind me, they use a copper penny, if it leaves copper it has to be polished.
The holes need to be chamfered.

Post a pic of the bearings, they will tell more.

 

Thanks everybody for your answers

Here are the bearings :


Are they ugly or what ?

 

That engine has how many miles/kilometers? (8 kilos to 5 miles)
Those bearing are WELL used.
Looks like normal wear,tho I hope thats reflection color on the bottom edge, of the bearing in the bottom pic.
Good luck on the crank turning.

 

If I can see a mark on journals, it's off to the shop for rework. Pictures can be difficult to read tolerances from, only a reliable shop will tell you if the part is re-workable!

Ensure that whatever shop you bring it to, that they chamfer the oil holes.

 

Oops, .050 under are available as shelf bearings for big blocks and V-6 engines only, they stop at .040 for smallblocks. Think about this: .040 represents just under 2% of the original journal size. Chevy's older "small journal" rod pins were 2.00" (.100 under current use sizes which is a 4.75% cut) and can be cut to Honda rod journal size of 1.889" which is a full 10%. If the crank is reground correctly with a wide radius on the filets, it'll actually be stronger than when it was new. If it's a cast iron crank, they are not hardened like steel cranks so you don't have to worry about cutting thru into "softer" material. I had this same discussion with my local crankshaft grinder and he said he'd never run across a hardened cast Chevy crank and he's been grinding for over 30 years. By the way, I'd have the oil holes chamfered as well.
That said, it looks like a .010 under will easily clean up the small ridges on the journals and should get most of the bad spot. Polish that small spot if it makes you feel better, then run it. As long as there are no raised edges on the ding, it won't hurt a thing. There's NO REASON to turn that crank down until that ding disappears, just enough to get the journals smooth. The ding looks to be directly in line with the oil hole which puts it right in the center of the bearing where it can't cause any problems.
How many of you guys have actually seen a crank break on anything other than in a full-tilt boogie seriously abused engine? I hang around a performance shop a lot and haven't seen more than 3 or 4 broken cranks in that time and a lot of these are cast crank budget circle track engines. Matter of fact, I've seen two "Hank the Crank" crankshafts broken and those ain't cheap pieces. Both were 4340 billet $5000 crankshafts.
Make sure you get the block cleaned well, it's generally crap that's left in the oil galleys that cause the bearing and crank journal ridges that yours shows. With no copper showing yet, that bearing is not that bad. I'd have the rods resized as well, the wear pattern should be uniform all the way around, not just at the very top and bottom of the rod's big end.
If you plan to beat on this engine hard, now would be a good time to upgrade to a steel crank.
All just my .02, of course.

 

The first engine that I ever rebuilt was a two-bolt 350 about 20 years ago. Of course, while taking it apart, I dinged the [cheap stock cast] crank in a couple spots. My shadetree mechanic friend who was at the time advising me told me that if the journal diameters were within OEM spec it would be fine to just lightly knock the tops off of the nicks with a half-round jeweler's file, then lightly polish the journals with strips of 500 grit emery cloth. It was a budget motor for my '72 Chevy truck, so I followed his advice on the assurance that everything would be fine. Now, this engine never saw more than 5000-5500 rpm during its entire life in my possession, but I did use it to pull my race car, trailer, tires, tools, parts and baggage up and down the west coast for the next four years numerous times as well as drive it to work and back every day, then pulled it out and sold it to a guy for $400. That was after about 50,000 miles. At that time it was still running fine and not using so much as a drop of oil. As for chamfering the oil holes, if you're building a race car then go buy a Chinese 4340 piece and chuck that stock POS. I'm sure FedEx or UPS isn't that much more to merry old France than it is to USA (unless the French gov't. actually stands up to the Chinese and levies appreciable tariffs against such products). If that part is just going to be used in a mildly-hammered driver I'd run it in a heartbeat. If you're really worried, have it magnafluxed to check for cracks. If it's not cracked (and I suspect it isn't), clean up those nicks as mentioned with a jeweler's file (again, you don't have to remove them completely, just dress the tops off so nothing protrudes past the journal surface) and lightly polish it. Clean out the oil holes with gun brushes or some other such device, and run it. With the price of Chinese aftermarket pieces nowadays, it's really not worth it to spend a bunch of $$$ (or Euros or francs or whatever they're using these days) having it professionally cleaned and polished. As for the bearings, yes, they're worn out and you better get new ones- I don't recall reading how many miles you had on this engine but it would appear to be somewhere north of 100,000. Best Wishes.

 

Thanks guys
Engine is the original one and have about 100K miles on it.
Plans for the Vette are mainly street use but I'll sometimes hammer it hard ! (I often pull my C6 to 6K rpm)

I don't know any serious shop in my area who can polish my crank and I just got my Summit parcel with new std bearings.
I found a Scat steel Crank on ebaymotors at NorthernAutoParts that'll cost around $400 to deliver.
As the crank was the only part I didn't replace yet, I'll certainly stay safe and pull the trigger.
I just ordered KB hypereutectic slugs and Summit Stage 1 rods when I found a crak when cleaning my pistons.

My only regret is not to have get a stroker kit before
If I'd know...