So after 15 years of faithful service, an enforced 5 year holiday (owing to a cracked transmission drum) and a recent ressurection with a completely overhauled engine and trans, I was to say the least, pretty chuffed to have the T back together and pulling like a train.
New pistons, new whitemetal, zed head, alloy manifold, reground cam, possibly the best built trans and magneto I've yet put together. She made it to the wedding on time too.
Except last night it broke the crank and the rear web out of the block.
This has happened to me before, with no real warning there's a god awful clatter from the engine that makes you jerk you feet from harms way, but as soon as you realise and dip the clutch, it just stops dead while you roll to the roadside.
This motor did make a curious noise a few times though. Under light load it somerimes had a bit of a ring to it, that if I'd had to hazard a guess was from the new alloy timing gear on the old crank gear. Perhaps it wasn't so innocuous.
I suspect the (long passed) very reputable old bloke who did the bearings and built the short engine... didn't crack test the crank.
I was just getting used to having my old friend around again...
Can anyone shed light on what's happened? It doesnt appear to have come from the journal radius... but there's an odd little crack (runs vertically in these pictures) right in the middle of the break.
Ive tried to get a few angles and lighting conditions, these still have oil on them, but I'm not quite the metalurgist needed to diagnose this is just a fatigue issue?
Just hours before the old girl was holding court with Barry the Labrador entertaining the tourists.
I don't know Anthony,
Looks like a bunch of different reasons...most of which appear to have been a long time coming.
I don't like guessing on photos of cranks...nor having the UPS man wonder why all the delivered boxes weigh the same...
Here's what you do...look real close with lots of light making shadows go away. The dirty areas have been forming for a while (and in some parts of the photo show the oil and oxidation has crept into a previous fissure. Look for what looks like waves, (or what looks like tidal lines along the beach.). These are a sign of bending flexure. The final cleave of catastrophe will lookalike sugar, but also look like a twisted swirl if it went in torsion...just plain sugar if it failed in bending. Bending failure is also indicated if the perimeter has miniature cracks all along the edge.
My guess and I shouldn't...too tight against the block mount and too much 4th main 'dipping'. I am also very, very curious...Ford did a horrible job of removing the skag lines (parting lines) in the throws. From here, those look polished? maybe even nonexistent ? If so, the 'visual' perhaps wrongly 'suggests' that that is somehow a folded forge throw and that lightning streak 'could' have just been to cold at the hammers right from the beginning.
Sorry I can't 'see' more or even closer guess. A break like that is in fact a little 'odd', but definitely induced flexure from 'something'
So sorry to see this, hopefully you have another engine that can be built up quickly to get you back on the road.
Thanks for the input George, I have only done a few hundred miles so it's not been a long time in my hands...
Dad and I have always wondered if many of these cranks were cracked by the hammers that forged them, we've found good ones are as few as 1 in 5 once you've magnafluxed a few dozen.
I know the balancing and skag line work done by Ford was pretty rough, just out of interest I've chased a crack out of one with a die grinder and a carbide burr, because I worked in the shop with the crack tester. We didn't use that crank but having seen some parts prepped for performance work over the years so I did once wonder if they could be made better by linishing and polishing, or shot peening and heat treatment processes... but Scat have scotched that idea. I'll have to start saving because as much as I admire the bent wire, I'll be buggered if I'm ever putting another one together.
That looks similar to my crank. See the picture on "my engine had a miss" Mine failed between the center main and #3 cylinder.
Its odd that prior to these two posts, the crank fractures that were posted appeared to be near a journal, not in the middle of the web.
I've often wondered if these guys set things up to fail eventually. From Arnold and Faurote "Ford Methods and the Ford Shops"
Wouldn't worry too much about the crankshaft straighting.
That method ranked up there with how the pistons were fitted
Phil Mino that little snippet is fascinating. It confirms my admiration for Ford's crankshafts and makes me wince in equal measure.
If anyone is up for some T era testing... I wonder if a SCAT crank would be so resilient?