Crank Question...

[Stborden]

I took the crank out of my 455 72 Cutlass Supreme to a machine shop and when they magnafluxed it I guess it looked bad. The guy that runs the shop told me it had been welded on twice, the mains and rod surfaces were both .030 under AND it had a crack in it. So now I need a new crankshaft.
In a completely street engine(daily driver) what do I need to look for in a crank? Is that new cast steel one from Eagle obviously the better choice or do the rebuilt Nodular Iron ones still hold value? Is there any way to verify that I'm getting a decent crank and not one that has been welded and reground several times? Is a brand new one for sure going to last longer and need less attention than a rebuilt one or is it like the block and it takes several years and rebuilds until the metal "settles"? Ultimately what I'm looking for is reliability and durability. I really want to be able to beat up on this engine and not have to worry about my bottom end fragging out. Obviously cost is a factor but if a couple hundred can buy me peace of mind then I suppose I'm willing to spend it.

[Cutlass69S]

you're asking million dollar questions. In my opinion, you can pretty much trust any new crank, I would stay away from rebuilt cranks, I would settle for re-ground cranks anyday. I've ran reground cranks in every engine I've ever built and have never had a problem, line up a reputable machine shop, some send there cranks out to get re-ground, fluxed, balanced, etc. some do it in house, either way, a reputable and established machine shop goes a long way. Tell them what you are building and what you're building it for, i.e. mild to moderate street, race, or daily driver, maybe even tell them the HP you expect to push. They will tell you what you need to know. trust your machinest or get a new one.

[88 coupe]

Originally Posted by Stborden

........ it had been welded on twice, the mains and rod surfaces were both .030 ........

Not a problem.

Originally Posted by Stborden

........ it had a crack in it ........

That is a problem.

Originally Posted by Stborden

........ what do I need to look for in a crank? ........

One that is not cracked.

Originally Posted by Stborden

........ Is that new cast steel one from Eagle obviously the better choice ........

check here, and pay particular attention to the last post.

Originally Posted by Stborden

........ do the rebuilt Nodular Iron ones still hold value? ........

Rebuilt? Not a problem.
Nodular? All Olds cast cranks are nodular iron.
Value? Check the "Parts for sale" sections in the Olds forums and/or post your needs in in the parts wanted areas.

Originally Posted by Stborden

........ Is there any way to verify that I'm getting a decent crank ........

If you cannot do it yourself, have your crank grinder check it for you. Or, he might be able to get one, from his core supplier.

Originally Posted by Stborden

........ not one that has been welded ........

Building (welding) material up, on the rod journals, has been a common way to increase a stroke, since the forties, and it is still a valid part of the operation.

Originally Posted by Stborden

........ and reground several times? ........

How many times, has nothing to do with anything. How much, is what is important. The limit (with stock rods) is solely dependent on what bearings are available. For instance, my 425 crank was ground .060" under, in order to increase the stroke by .050".

It has been common practice to increase the stroke on a cast 455 crank .250" by taking .125" off the main side (offset grinding) of the rod journals, and using 2.5" bearings.

Originally Posted by Stborden

........ Is a brand new one for sure going to last longer and need less attention than a rebuilt one ........

In a given situation, that would be impossible to predict.

Having said that: A properly ground (and modified) crank would be more likely to survive at higher RPM, than one that is not.

Originally Posted by Stborden

........ or is it like the block and it takes several years and rebuilds until the metal "settles"? ........

If you are referring to the "seasoned block" theory, that was popular in the '70s, it has nothing to do with anything.

Originally Posted by Stborden

........ want to be able to beat up on this engine and not have to worry about ........

Unless you plan on approaching 600 HP, or so, concentrate less on the crank, and more on finding a crank grinder that is up to the task.

Originally Posted by Stborden

........ if a couple hundred can buy me peace of mind ........

Biggest mistake, most beginners make, is to overspend on parts and to "cheap out" on the machine work.

But, it's your money.

Norm

[kaz442]

I would go with a stock N crank. Find a good used one, not over cut and check the thrust surface for excess ware. Or find a running motor take the crank and sell the heads, block and accessarys to offset the cost of it. Just find a good machinist that can do the job correctly and set up you clearances right. Where are you located? Maybe somebody nearby can recemend a good shop. If you near NJ I have a great shop near me. Jkaz

[J-(Chicago)]

I have a FREE crank if you're near Illinois. I just ruined a motor at the drag strip 2 weeks ago. #3 rod bearings slipped underneath one another and fused themselves together from the heat. Crank has some nasty scoring now, and It won't be worth machining $ for me because I have another running 455 ready to drop in.
If you want a freebie to have your machinist analyze and possibly regrind I have you covered. However I can't guarantee that it's not a paperweight now.