I broke my toy in Detroit!!! Updated Jan 2020

[Bolted to Floor]

Thanks for the feedback Doug.

I am done with this block and have acquired another that cleans up at .020. New rods, crank, bearings, and rings are in the garage. I'm waiting on pistons to take it all to the machine shop. I will take the heads to him also for inspection. I will see what I can do about a rebuild on the lifters.

I was showing some of the parts to a friend today and his comment on the cam was it looked like valve float since the chatter marks were on the ramp down side of the lobe. I don't know that my pictures show it that well.

I was going to try to sell some of the rods. Number 1 was a gift to a friend. Number 5 will be wall art for me. Number 2 is questionable to me due to the bearing condition. At $95 for a single from summit, I don't expect to get much for the rest of them.

Is there a market for garden variety main FE caps??

C-reed, mine is a Comp Cam bought in 2017.

Yes, Mark, it was a bummer. We had drove up from Houston to Adrian Michigan for the Mustang Steve Bash that took place the day before. We had more sight seeing planned for the way home. We still got to do a lot of that, but we lost a day rounding up a truck and trailer. I hope the car will be ready, whether it is or not, I will be in Surfside Beach SC for the 2020 Mustang Steve Bash. The Bash and Reunion are on the same weekend this year. I would love to make it to one of the Reunions.

To all, I want to be clear that I'm looking for a better understanding......to use it as an expensive learning experience, nothing more.

[cjshaker]

John, I'm surprised more people haven't chimed in.
Unless you drag raced the car, a crank failure is obviously a rare thing. I'd have to guess that it was a fluke, a bad luck deal, but I'd look the machine work over carefully on that radius, and get some input from the guys here who machine that stuff. A bad machining practice on a radius could have led to that failure, and you don't want a repeat of that!

Heck, I could be wrong about the radius failure, but it sure looks like that's where it started, right at the apex of where the radius machining ends and the forging starts. And if that's the case, it seems to me that that's not just a coincidence. Has the crank led a hard life? Drag raced? Abused in a previous engine? Was it magged?

[Bolted to Floor]

The radius was brought up early on and could be a possibility. I will get some better pictures of it, but I’m not sure how well it will be for a comparison to what one should be. Fluke or bad luck is a possibility with a 50 year old part.

Drag raced, no. Heavy foot, hard acceleration, yes.

I took the crank out of a 410 in a pick a part about 1990. It’s been moved from house to house over the years standing on end in my garage till it went to the machine shop. It was magged for cracks and checked good. Prior to that, no idea.

[dcm0123]

Was the dark stain shown in the break area on the 7'Th and 8'Th pictures from the bottom there when it was removed from the car?
This does not look normal and may be an indication of why it cracked.

I would discard the block or have someone check it for bearing bore alignment and fractures before you use it.
I recently took apart a Ford 302 which had a broken crack. The block was severely cracked as well.

[Bolted to Floor]

The only thing I wiped off was some excess oil.

I won’t be using the block again.

[My427stang]

The only thing I wiped off was some excess oil.

I won’t be using the block again.

I initially was going to tell you not to replace the block just for a bad crank, but went back and saw it was a .060 over 390 not the 428 I thought it was and changed my tune.

Cranks break and often in that general area.  A bit of balance issues, belts pulling on them, a previous cut that may take away a little margin of fillet, and you have what you see.  You could easily push the pistons out, take a good look at the block and just stab another crank in, and it wouldn't scare me to tell the truth unless you find that a cylinder split.  However, given the .060, and quality of the car, I'd likely build something stronger in both durability and horsepower, seeing that you are forced to take it apart and have good supporting parts already.

Honestly though, a broken crank is a reason to look at a block closely but not itself a reason to swap a block.  Regardless, if motivated to do so, it'd be nice to do a min overbore internally balanced stroker and go with nice light components. 

[Bolted to Floor]

Thanks for the feedback Ross.