Crank snapped in two. Oil starvation or crank flaw?

[nsracing]

It is an old crankshaft that had been cycled over several its lifetime - bound to happen. I say that part gave itself a long service life.

Looks like a Demello work - I like their work a lot.

[Braukuche]

I don’t know why anyone would use a 30-50 year old crank these days when you can buy new ones. Same with cases, these parts are way to old and gone through too many wear cycles to withstand too much abuse. A stock build yeah, or if you have a 25 or 36 Or 40HP but a 1600 based performance build offers too many good new alternatives.
_________________
Go Reds! Smash state!

Retirement is here!
1956 Ghia
1959 SO-23 Westfalia
1960 double cab
1960 Baja Bug
1963 stretched double cab
1962 Golde sunroof Ghia
1963 356 B coupe
1963 Notchback
1967 21 window less rusty now

[modok]

"new" cranks are a better deal at the moment, YES, but

Keep in mind that it wasn't this way in the past, and the future is unknown.

There is a saying about
When things seem too good to be true....


or, it is fortunate your crank broke during... a time of crankshaft abundance.

[Shane Tuttle]

[slayer61]

[SLAKKER]

Either Metal Fatigue or the radius journal was not ground
to spec

[RickS]

[mikedjames]

Maybe, hard to tell from the pictures:

One end of the break on the surface of the crank seems pretty close to the end of one of the welded seams for the added counterweight.

Maybe the welding left some stress in the metal.
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[risk]

[Ohio Tom]

[quote="Clatter"]This happens a lot, actually.
Just like yours, right next to the center main.
Aftermarket, factory, counterwieght, stock, stroker, doesn't matter.
When your number comes up, it comes up.

It's not something you did wrong or anything else.

It just happens.


Hopefully your line-bore is still good..[/quote

Spot on..

Looks like the crack started from the journal radius, just like they always do.

This is the risk you take when having a high-milage crank as the base for a welded C/W crank.
I know they get inspected before chosen for the job, but it's still a Used part they start with.

However, it can happen to any crank and often does.

Even stock motor broke crankshafts...

[Shane Tuttle]

[txoval]

Demello is no longer around

[71ghiavert]

This was an American-built, high-quality crank on a German core. Highly recommended even here on Samba. "Stuff," as Shakespeare so wisely said, "happens. You know?"

Trying AA next time and hoping for a different outcome.

[txoval]

Spend a little more and buy a Scat 4340 crank...last one you’ll buy

Would have to move to a 78.8mm crank though

[71ghiavert]

I'd buy the Scat if they made a 74mm, but I don't think they do. If I move up to a 78.8, then I think I'd need new pistons to go with my 5.35 rods, and might get into problems and a lot of extra work dialing in deck height and compression (heads were chambered for 9:1 with the set-up I have).

With the same size replacement crank, I'm likely to be very close as is. I hope to keep the fix simple--new crank, new bearings everywhere, new rings--and get back on the road as quickly as possible. The engine felt really good before it blew up!!

[oprn]

I bought an AA one in stock stroke. It cam unbalanced and at first my balancer/machinist refused to balance it. "Too far out" he said. He wanted me to return it but the guy I bought it from refused to take it back saying the next one won't be any different. I put them in touch with each other to fight it out. In the end the balancer used what he called "unconventional means" to balance it.

I posted a thread about it here and didn't get any comments really so I went ahead and used it. There is only about 4 hours running on it at the moment and it seems fine...
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[txoval]

Scat makes a 74mm crank in their Billet versions, but those are $1800

I hear you on keeping the fix simple. If you change your mind, get the 78 crank and buy B pistons...can still reuse your cylinders. No need for forged pistons

[Pruneman99]

I got a 76mm 4340 EMPI and it was near perfect for balance out of the box. Actually the worst part was the OG flywheel I had them drill for 8 dowel. The 9 spring OG pressure plate needed a little bit.

Idk how the 74mm ones are.

[bugguy1967]

[evanfrucht]

Empi 4340 or Scat. I think they are both the same stuff, same factory. Both have a good track record. Empi is usually cheaper. Car Craft has the best deal online.

Sounds like you just go unlucky. Forging varies each time, sometimes the grain pattern/metal structure just doesn't quite end up the way it's supposed to. Perhaps the drilling weakend it (drilled to close to journal in error) Maybe the welder screwed up or the heat messed something up. Who knows why it happened.
_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )