Hey Guys (and Gals),

I have broken down the 327 from the 62 I am restoring and have a couple of crankshaft questions. 3 or the 4 connecting rod journals look and feel great. I will mic them today. However, the #3/#4 journal is badly scored. Looks like some grinding will be required. Now for the questions so I will feel somewhat armed when I go to the machine shop..

1. Can I have only that journal machined?
2. What is the max they can cut the shaft safely?
3. What was most likely the cause of the scoring? I did find a broken top compression ring in cylinder #3 as well? Any relation?

Thanks,
Doug
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Grind one journal on the crankshaft? NO, NO, NO ! ! ! Unless you have someone who can do it in the chassis and I don't know of anyone around today who still has the equipment and the knowledge of how to use it.

When I was in the business and the crankshaft was out of the engine block I wouldn't do it and I do not know anyone who would today.

That would make a bastard unit out of it and, somewhere down the line, someone else gets stuck with it. Besides, the entire shaft needs grinding. If one rod journal scores, the others were not totally spared.

On the question of how far can you go undersize you can go to .030 with no harm done. The crankshaft will service fine. If you have light scoring you may end up at .010 or .020 undersize. No problem.

Cause of scoring, FRICTION. Usually caused by lack of lubrication to that journal and resulting in excessive heat. Check the bottom ends of the connecting rods and see if you have bluing on the metal due to heat. Don't be afraid to recondition the connecting rods while you have it apart. AND install new connecting rod bolts during the reconditioning process.

Rich

 

As for cause, I would say foreign material is the number one cause of scoring. Before I finished your post, I was going to say dirt, but it very well could have been chips from the broken ring. I wouldn't get too hung up on spending a lot money on saving it. Unlike a "correct" numbered block, the crank isn't a restoration item, and decent replacement cranks are available at affordable prices.

RACE ON!!!

 

Have the whole crank ground. If not then you have different weight bearings and it becomes a balancing issue. Aside from that, you really want uniformity in your engine.

Only have ground the lowest amount needed but as far as I know, there are bearings that go as low as .060 undersize. Trust me, the amount of undersize is a non-issue on these cranks. People get worked up if a crank is more than .010/.010 and that panic has no merit.

The most likely cause is dirt and contaminents in the oil. The broken rings would not have caused that.

 

Have it magged and turned .010/.010 and over the years we have seen single rod journals turned on cranks before some right form GM and and granted a .010 bearing is heavier then a standard bearing but because the jornal is now smaller it really evens out and should not affect the balancing.

And if your changing the pistons and they are a different weight you may want have it balanced.

Good luck with your build Carl
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With out factual data your just another guy with an opinion!!!

 

Are you discounting debris from the broken ring causing the scoring? I wouldn't.

RACE ON!!!

 

That small journal 327 has a steel crank - keep it (good stock forging, tap it and listen to it ring). Have it turned down and if possible get the journals radiased.
I have been surprized at how much gouging a crank can live with - well at least on the street. I watched a friend take the crank from his Alfa Romeo with a gouge nearly 1/4"wide x1/4"deep x1"long on a main journal but it was nicely polished out and not a problem to the bearings. That crank was too expensive to replace and the owner continued to drive with it for years.
BTW u can polish out small scratches with 400 grit or smaller (i used 600 then 800 grit i recall). Just cut small strips then half wrap the journal and sand away until u can't feel them with your finger tip.

To answer your question more directly though it dosen't make much sense to only machine 1 journal.


Good luck Doug and please share your results.
cardo0

 

Yea, I have to admit that I kind of did. You would probably get some particles from a ring break but I doubt it would be much though unless it really broke in several pieces.