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1300fwd crankshaft woe


PeteStupps

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Hello everyone,
Just made a very upsetting discovery on the 1300fwd engine I've been slowly stripping and rebuilding. I hadn't taken the timing cover off until today, because the crank pulley nut was being awkward (mostly because I didn't remove it while the engine was attached to the car).

Now what do I discover, the woodruff key slot is completely shagged!

Firstly, is this crank a write-off? I think it must be, can't imagine you can weld and re-cut the slot.
Secondly, is £50 inc postage for a crank off ebay reasonable? Because there might be one that's suitable or it might also be wrecked in some other way. It seems cheap to me, as I wasn't expecting to see one!
Thirdly, what could have caused this? Isn't the key supposed to snap before lumps fall out of the crank?!

It's just a standard 1300 engine, single-carb. There was no history with it but so far the engine has appeared to be untouched. There was also some damage to the distributor drive gear which I found a few weeks ago. Other than that it's been in very good nick.

Thanks for any advice!

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I think, IIRC, 1300 FWD cranks came in two flavours.  Those with a parallel nose (earlier ones I think and pretty sure the crank is the same as 1200 & 1300 Herald/Spit) and those with a tapered nose - with pulley to match.  I think the 1500FWD also had the taper arrangement though I've not actually worked on one.

I think your pictures might demonstrate why they went to the tapered version - cyclic loads from the starter ring gear eating the key etc.

The book I have (proper factory manual) makes no mention of the tapered version, but I know they exist as the car I owned many years ago definitely had a taper fit and I remember it vividly as it was an absolute sod to shift.......  Probably interchangeable so long as you get the matching pulley etc.  If you stick with the parallel arrangement, make sure the nut is done up proper tight!

Nick

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I don't know what the third variation is and don't have a parts book.  I suspect that the early version will be the same crank as the RWD cars and thus easier to find, but that won't help with the pulley.  A complete set of the taper parts would be considered an upgrade I think.  

We have some FWD experts about - hopefully they'll be along soon to explain!

Nick

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Yeah, my one is also listed in the Spitfire Mk2 parts book (haven't got a mk3 book). In the FWD parts book there are 2 cranks listed exclusively for the single carb, then another listed for all TC's plus the latest lot of SC's. Haven't got the book to hand but I thought it just had one flavour of crank pulley; will check when I get home.

I'm a bit slow on the uptake, of course these have the starter ring at the other end from normal! Hence that little key slot is getting a load of jolts that it wasn't originally designed for. Of course of course. Although the worst damage to the key slot seems to be on the wrong side... hmmm.

Has anyone else seen this sort of thing? Like I said, I thought the woodruff key was supposed to be softer so it wouldn't scrap the crank.

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I have seen this kind of damage before, though not on a Triumph.  Caused by a loose crank pulley bolt.  That engine had a fairly hefty torsional vibration damper on it and had been "rattling for a while" to quote the owner.  Eventually the cam belt became involved as well and that was the end of the engine.

There are all kinds of forces acting here and the damaging ones (torsional vibrations) are probably not the obvious ones.  Trouble is, as soon as you get any backlash it gives things and "run-up" and increases the impact.  You'd probably get away with it (or at least have longer before damage became serious) on the RWD version of the engine as the pulley is lightweight and driven loads are low.

Nick

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Hi Pete,
As others have said the early 1300fwd cars had problems with the crankshaft nut coming undone and then damaging the keyway. Personally I would go the route of fitting a later crank with the tapered nose you'll also need the associated pulley there is also a special wavy washer that fits between the pulley and the timing gear, this replaces the oil thrower washer, this is important! Also it uses a parallel key rather that the woodruf type.

What condition is the old crankshaft in other than the keyway slot, a machine shop should be able to cut a new keyway on the other side and also cut the taper as a later crank, But using a replacement crank would be the easier option.

The third type of crankshaft was on very early cars the first six months or so these had the scroll type rear oil seal as per Mk1-2 Spit and 1200 Heralds

  

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  • 1 year later...

Hello all,

Blimey where does the time go? Just to update this old thread, with humble thanks for all the useful advice, I had the original crank machined to fit the later tapered pulley and associated bits. Got all the ingredients from Mick Dolphin.

Then commenced a very slow rebuild, which I'm pleased to say is now complete! More or less. After curing most of the initial leaks and whatnot, took the car out for a short run on Saturday morning and it drives nicely. 

Bit of a clutch issue though. It has a stiff grindy feeling when operating the pedal, which is not evident when engine isn't running. Gears are quite hard to engage as well, which suggests slight clutch bind maybe? Biting point is fine though, after adjustment.

One thing I wondered about - I fitted a new input shaft but didn't grease the splines. Would that cause problems? Or is release bearing or pressure plate more likely culprits?

 

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As for the clutch problems, how old are the hydraulic components? In my experience the master cylinder in particular can seem to work but fail to give full movement to the clutch mechanism, leading to slight clutch drag. Might be worth replacing the m/c and resealing the slave (less to wear out in the slave).

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Cheers Dan. it's a brand new master cylinder, as the old one was full of crystallized fluid. I think there's plenty of movement, as I say it doesn't bite particularly early. Just stiff gearchange. Plus there's this graunchy feel to the clutch pedal, all the way through the movement. But that isn't present when engine isn't running, so it's not the pedal mechanism.

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Thanks Nick, new release bearing is on its way to me now courtesy of James Paddock, for half the price Rimmers are asking! 

Sadly Mick Dolphin has sold his last fwd clutch plate so I'll have to get one off eBay (there's a little bit of clutch judder so might as well change plate at same time as bearing).

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