Those who don't mag their cranks may live to drive over one- not a good thing. After one major failure which took out a block, pan, rollercam, two rods and pistons, I check them every time they come out of the block. I found a small crack in an aftermarket crank with 100 runs on it, which surprised me.

Was it an ex- fuel crank?

i don't know the full history of the crank in question. it's a factory forged 440 crank. i was told it had been in a motor that was sprayed with NO2. i don't know how much or how often though.
the plan was to use it in a fairly mild low deck combo after cutting the mains and counterweights down.
i sure can't blame a 40+ year old crank for finally giving out after being abused. i'm just glad the owner let us check it out before doing a bunch of work to it. no harm, no foul, we found a good useable crank for his project.

This is part of what shows that a builder cares and taking the time to post pics and discuss the issues is a big plus in my book.

Yupp....That does show some class!

this reminds me of when i first met Dan. I showed up with boxes of junk parts and he wouldn't let me leave till all the parts were checked out so he didn't have to make the dreaded, "yours parts are junk" call

Wow I have never seen what that process looks like. Thanks for posting the pictures.

Come on Dan, a little 320 and a shoe lace ought to clean that right up

Cool pic!

Great thread! And good find!
I see cracks like that all the time, but on aircraft components. Scary stuff.

Hey Dan, That Crank Looks Familiar. Yes This Was Mine.

Dan what current do you use? AC or DC? DC can pick up shallow sub-surface indications while AC will normally only pick up indications that are open to the surface. Also product do you use to check alluminum heads/rods? I know alot of people have seen Magnaflux red dye penetrant but I'm willing to bet very few have seen flourecent penetrant which is actually way more sensitive then mag particle depending on the level of penetrant you use.


Just to give you guys who are interested an idea how the magnaflux works. You have a few different ways you can magnatize a part. 1. you can use a hand yoke. The advantage of these is they are portable and can get into smaller areas. You can use a yoke for pretty much any part you want to mag. but you can only cover a 6" area at a time. The second way of magnatizing a part is to use a magnaflux bench. The advantage of these are you can control the amount of amperage that you put into a part. You also can magnetize a whole part at once which saves time and money if you have multiple parts to do. Third way is you can use another type of magnaflux machine that uses cables. (kind of like welding cables) The advantage of these is they are fairly portable and can do very large parts.

Now for how the process works its pretty simple you magnetize a part while applying flourescent particles. These particles are made up of kerosene/water and iron. If there is a crack in the part it will break the magentic field and cause the flourescent particles to line up along the break, when this happens you get indications that look like the pictures that Dan posted.

Thanks for the Post Dan, it's very important info & is a reminder to never assume anything when building an engine

good post and cool to see a pic of it broken in 3 places thats quite bad,or good that it didnt brake killing alot of other parts in the process atleast.

does people/builders still weld cracked cranks?

Its a little difficult to see but Im assuming the crank is OEM journal? With that being said there's proof for the need of large radii fillets, Chrysler done real bad with their under cut design.

I agree having a crank magnaflux tested for cracks when the engine is apart is a very good idea (recommended).

Back in the years I ran a 3.915" offset ground factory 440 forged crank, it was cracked (not as bad as that one) after running 2-3 years.

Then in 2006 I built a new engine using a new Callies 4.250" stroke crank I bought from Dan. That crank was tested in Jan 2011 and was completely crack free after 5 years and over 600 passes. So it went back in for more service. The steel rods were tested also, and were good to go; while it was apart I put new rod bolts in them.

I think it's a good idea to put this entire thread in the Q&A forum too.