I need a solution like this

https://www.compcams.com/big-block-chevy-crank-nut.html

I have these for small block chevies

I have some Nissan L20b's that I need to try to get free. We popped the crank shaft pulley trying to turn a frozen engine

@Captain Obvious

You feeling board in confinement??

I did some googling to see if I could find one. The one I have is too small. The Nissan crank snout is larger. I don't know if the BB chevy would be closer in size. If I found something close, I could modify it

Looks like

SBC is 1.255"

BB Mopar is 1.542"

BB Chevy is 1.610"

Mic'd the Nissan crank @ 1.380"

Maybe the SBC could be opened up by .0625"? a 1/16th

I don’t have a solution for the crank nut, but I’ve managed to un-stick a couple of engines in the past by leveraging a pry bar on the flywheel. If it’s on an engine stand you can use one of the mounts to leverage against, but you may need a second hand to prevent unwanted rotation from the engine and / or stand. Otherwise a bolt through the block where the bellhousing would go has worked. I just work the flywheel both directions until it breaks free, but I’ve had to let the penetrating oil sit for a few days first. On one I also had to help motivate it with a brass punch and hammer. Just an idea, not sure what all you’ve tried yet. 

I had considered that as a technique

I may have to use some form of hammering too.

Pistons have been soaking in PB Blaster for a week now

Hmmm. If I have appropriate sized stock, I could make that.

Does it have to be hex on the outside? Would something with just two flats on opposing sides work? Or square? You wouldn't be able to use a socket on it. You'd need to use a large open end. Would that be good enough?

I'm thinking that since the application is to unstick a motor, you might be putting considerable torque on it and a hex would be better. But thought I would ask to see what you thought.

I appreciate that Bruce but I may have found a solution

Summit racing had one that appears to be within 0.005"

I ordered it. Expensive but would be a nice tool to add to the chest. I suspect the other L blocks have the same snout diameter

As to the other questions square would work fine because I have a 24" crescent wrench like Guy bought a couple of years ago

Should have the tool midweek. I will update then

@Patcon - glad you found something that may work.

I would have been digging through my stash looking for a busted balancer and recycling it for the purpose at hand.

I hope the key way widths are the same between what you ordered and the L-series.

Charles,  Cool. If it doesn't fit and you can't fix it with a file, let me know. If it's not hardened, I can modify it to fit.

Wayne, I was thinking the same thing! So where does the rubber junction come in on the damper? Is the center portion isolated from everything else. or is there something you could machine into a "wrench attachment point"?

I dont have pictures but the balancer that was on it was already damaged (the pulleyswere chipped). We welded a 6' pipe to it as a cheater. The hub of the balancer popped open. It actually broke pretty easy. Now it's possible it was already cracked from the PO beating on it but it made a disappointing tool!

I'm looking at some old pics of when I cut one of the pulleys off a two-pulley harmonic balancer. (Academic project on a damaged balancer.)

Don't remember if I ever posted these in the past, but here's a couple pics:

The point is... I'm wondering if the nut you purchased is going to work. First, the corners of the hex need to be small enough to fit inside the front oil seal. You could remove the front seal if you need to (since you're probably going to replace it anyway). Second, you'll need enough length on the nut to a) engage the key on the crank, and b) still have enough length sticking out of the front cover to get a turning tool onto it.

If the front cover is completely off the motor then neither of those trouble spots apply, but if the front cover is still installed, I'm thinking things might not work out.

Front cover is off. Actually the guy beat the damper off to sell the front cover. I didn't realize until I got home I didn't get the cover and I learned it's a unique cover! So I contacted him about that. We eventually got around to the truth that he sold it, so the 2 blocks I bought from him were paper weights without the cover. I have since sourced a cover from the Seattle area. So we again have promise

Good.     Wait... Not good.   You know what I mean. 

So your nut will work. Too bad about the front cover.