Technical Crankshaft snapped!! Need help sourcing parts please

[plantpot50]

So during a little drive out on Saturday, my car had a protest and the crankshaft snapped!!! It seems that my engine had been tuned to its limits and as result, failed!!

I am now trying to source some parts to get back on the road and any help of where to source would be gratefully appreciated!!

The mechanic is concerned about the amount of movement from the crank inside the block and has advised a replacement 650 block.
The engine has a 700cc kit on it and both conrods need replacing- the garage has measured them at 117.5mm between centres - I dont know where to source them from!
I'm in also need of a crankshaft, main bearings and new oil pump.

If anyone has any spares on their shelf they would be willing to sell or can advise where best to purchase from, I would be extremely grateful.

 

[Toshi 975]

Oooh painful but not unheard of
A pal bent one crankshaft and snapped another but he was running a turbocharged 100hp+ engine. His only option was to go for a forged steel crankshaft which are over £1.000. It is not surprising that the cranks are prone to failure as the same crankshaft was used from the humble 500 through the entire aircooled range up to the 2000 126 models. The only production variation is that fitted to the water cooled 126 Bis which is said to be stronger and have better chacteristics at higher revs. These are interchangeable with the standard crank.

The profile is much closer to the racing cranks and I have fitted 3 or 4 on engine builds with no problem.
I have a couple of reground cranks here along with the bearing sets but no spare Bis crank at the moment. I have all the other parts you mention as well.
Are you running a distributor based ignition?

 

[plantpot50]

Oooh painful but not unheard of
A pal bent one crankshaft and snapped another but he was running a turbocharged 100hp+ engine. His only option was to go for a forged steel crankshaft which are over £1.000. It is not surprising that the cranks are prone to failure as the same crankshaft was used from the humble 500 through the entire aircooled range up to the 2000 126 models. The only production variation is that fitted to the water cooled 126 Bis which is said to be stronger and have better chacteristics at higher revs. These are interchangeable with the standard crank.
View attachment 420771
The profile is much closer to the racing cranks and I have fitted 3 or 4 on engine builds with no problem.
I have a couple of reground cranks here along with the bearing sets but no spare Bis crank at the moment. I have all the other parts you mention as well.
Are you running a distributor based ignition?

Hi Toshi,
Thanks for your reply, I'm running what i believe is a wasted spark type electric ignition.
Would you be willing to sell any of the parts?

 

[Toshi 975]

Hi Toshi,
Thanks for your reply, I'm running what i believe is a wasted spark type electric ignition.
Would you be willing to sell any of the parts?

No problem, I asked about the ignition as I have a brand new 126 EL crankcase up in my loft and the EL engine has no distributor Or hole for one. I also have a very good 126 bare crankcase in my garage, a new oil pump with new timing chain cover. If your pump is damaged or worn then chances are the timing chain cover it sits in will be as well. Are you intending to stay with a standard crankshaft or look out for a Bis one?
I can get some pics in the morning if you wish.

 

[fiat500]

No problem, I asked about the ignition as I have a brand new 126 EL crankcase up in my loft and the EL engine has no distributor Or hole for one. I also have a very good 126 bare crankcase in my garage, a new oil pump with new timing chain cover. If your pump is damaged or worn then chances are the timing chain cover it sits in will be as well. Are you intending to stay with a standard crankshaft or look out for a Bis one?
I can get some pics in the morning if you wish.

I'm edging in on your trading interests here, but I do have a BIS crankshaft that I will never use....the balancing worried me.

 

[plantpot50]

No problem, I asked about the ignition as I have a brand new 126 EL crankcase up in my loft and the EL engine has no distributor Or hole for one. I also have a very good 126 bare crankcase in my garage, a new oil pump with new timing chain cover. If your pump is damaged or worn then chances are the timing chain cover it sits in will be as well. Are you intending to stay with a standard crankshaft or look out for a Bis one?
I can get some pics in the morning if you wish.

I think I may stick with the standard crank, but be more aware of its limitations when driving!! Can you help with the con rods or advise where I may be able to source some?

 

[plantpot50]

I'm edging in on your trading interests here, but I do have a BIS crankshaft that I will never use....the balancing worried me.

If you want to pm me a price, it would definitely be a consideration!

 

[the hobbler]

I think I may stick with the standard crank, but be more aware of its limitations when driving!! Can you help with the con rods or advise where I may be able to source some?

Et tu Brute! I have found out, from personal experience, that the standard crank doesn't like being continually revved over 6,000rpm---my crank snapped at exactly the same place as yours. Luckily, I was only going slowly, on my way TO the 'rolling-road', so there was very little perifural damage. I eventually was able to buy a crank from David ('Toshi'). Con-rod wise, believe it or not, the Dino 246 con-rods have exactly the same big-end (crank journal) and gudgeon-pin (wrist-pin) dimensions as the 500/126 conrods.The only measurement difference is that the '246' con-rods are 1mm shorter--not a difficult problem to get around. When fitting the '246' con-rods the crankcase needs to be fettled slightly to give clearance. So, start looking for a written off Dino with the engine in pieces! Alternatively, speak nicely to David (Toshi)!

 

[plantpot50]

Et tu Brute! I have found out, from personal experience, that the standard crank doesn't like being continually revved over 6,000rpm---my crank snapped at exactly the same place as yours. Luckily, I was only going slowly, on my way TO the 'rolling-road', so there was very little perifural damage. I eventually was able to buy a crank from David ('Toshi'). Con-rod wise, believe it or not, the Dino 246 con-rods have exactly the same big-end (crank journal) and gudgeon-pin (wrist-pin) dimensions as the 500/126 conrods.The only measurement difference is that the '246' con-rods are 1mm shorter--not a difficult problem to get around. When fitting the '246' con-rods the crankcase needs to be fettled slightly to give clearance. So, start looking for a written off Dino with the engine in pieces! Alternatively, speak nicely to David (Toshi)!

Thanks Tom, I'm hoping Toshi will come to the rescue!! I phoned you earlier for some guidance but I believe you are away for a couple of days. Are you still running a standard crank in yours?

 

[Toshi 975]

I have installed a wellman kit in my Fiat 500 with a 650 cc engine. The engine starts much faster and has a better idle. I have doubled the ignition coil (dual-spark) It is a cheap upgrade that can be recommended.

If you want to pm me a price, it would definitely be a consideration!

Yes I can do that and in your situation I personally would opt for a Bis crankshaft if you can get one. You never know when you might be tempted to bury the noise pedal
is that con rod length standard? You can get them in different lengths but I do not know of any suppliers outside of Italy.

 

[plantpot50]

Yes I can do that and in your situation I personally would opt for a Bis crankshaft if you can get one. You never know when you might be tempted to bury the noise pedal
is that con rod length standard? You can get them in different lengths but I do not know of any suppliers outside of Italy.

I don't know what the standard length is? My mechanic advised that they were 117.5mm between centres and 160mm overall length.

 

[Toshi 975]

I don't know what the standard length is? My mechanic advised that they were 117.5mm between centres and 160mm overall length.

I am sure we can check that out. i have kind of a morbid interest in engine failures and when you say that the mechanic is not happy with the end float in the crankcase suggests that the broken crank has forced the crankcase out via the main bearings. I would guess that an engine of that spec would certainly had an alloy sump so was it fitted with a thick sump gasket? I was always told to use a thin smear of sealant on the alloy sump to increase the rigidity of the whole crankcase.

 

[plantpot50]

I am sure we can check that out. i have kind of a morbid interest in engine failures and when you say that the mechanic is not happy with the end float in the crankcase suggests that the broken crank has forced the crankcase out via the main bearings. I would guess that an engine of that spec would certainly had an alloy sump so was it fitted with a thick sump gasket? I was always told to use a thin smear of sealant on the alloy sump to increase the rigidity of the whole crankcase.

Great stuff, thanks David. It has an L shaped 5ltr sump fitted, Im not sure about the gasket but will ask the question tomorrow

 

[the hobbler]

Great stuff, thanks David. It has an L shaped 5ltr sump fitted, Im not sure about the gasket but will ask the question tomorrow

Yes, I have fitted a standard crank in my engine as the replacement. However, I have since fitted an "Abarth" style instrument cluster, so I can keep an eye on the revs; I now limit my maximum revs to 5,800rpm. I am away until Thursday evening, so feel free to ring me after that.
A "5 LITRE" sump! Wow---that is somewhat overkill! In the UK the 3-1/2 litre sump is all one usually needs. As David has mentioned, using a sealant instead of a gasket (rubberoid, but NOT the cork variety) between the sump and the crankcase, helps stiffen the crankcase.
Whilst I concede that my engine wasn't running very fast when the crank snapped, I noticed very little periferal damage. Basically, I fitted the new crank, new bearings (crank and con-rods) and new con-rods, shimmed up the crank end-float (about 10thou with the crank-nut tightened to correct torque).
It sounds as if your engine has been very much 'enhanced', so yes, your mechanic will need to carefully check the con-rod length as ther is a good chance that it is not standard. Look forward to chatting to you.

 

[Bleeding Knuckles]

Hi Plantpot, sorry to hear of your problem. The standard length rod's are 130mm I have these fitted with a balanced BIS crankshaft, the throw of the crankshaft is standard to provide a 70mm stroke in a 80mm bore barrel (total 704cc) the piston height (centre of wrist pin to top of piston) is 35mm if I remember rightly. I will point out that my head has been severely skimmed and we had to use a 0.50mm copper gasket to get the deck height/squish and C/R correct. I am aware that 118mm rods are available, but I don't know what engine size and application they are for! I would council you to measure all your parts before purchase as you may have an unusual build on your hands. I am aware that some crankshafts are supplied with an unusual throw for long or short stroke with differing rods so best to check this too. The stroke length of the barrels can be different too with many different piston heights and bore sizes available from Italy mainly. The principle use of the BIS crankshaft is that the counterbalance mass is much closer to the longitudinal centre line and thus enables higher revs with less crank flexing. All to often these engines are tuned up to perform well above their original level without any thought for the crankshaft / bottom end, as has been mentioned above 6000rpm the propensity is for the crank assembly to begin flexing about the forward big end with the obvious result!!!!
Ian.

 

[plantpot50]

Hi Plantpot, sorry to hear of your problem. The standard length rod's are 130mm I have these fitted with a balanced BIS crankshaft, the throw of the crankshaft is standard to provide a 70mm stroke in a 80mm bore barrel (total 704cc) the piston height (centre of wrist pin to top of piston) is 35mm if I remember rightly. I will point out that my head has been severely skimmed and we had to use a 0.50mm copper gasket to get the deck height/squish and C/R correct. I am aware that 118mm rods are available, but I don't know what engine size and application they are for! I would council you to measure all your parts before purchase as you may have an unusual build on your hands. I am aware that some crankshafts are supplied with an unusual throw for long or short stroke with differing rods so best to check this too. The stroke length of the barrels can be different too with many different piston heights and bore sizes available from Italy mainly. The principle use of the BIS crankshaft is that the counterbalance mass is much closer to the longitudinal centre line and thus enables higher revs with less crank flexing. All to often these engines are tuned up to perform well above their original level without any thought for the crankshaft / bottom end, as has been mentioned above 6000rpm the propensity is for the crank assembly to begin flexing about the forward big end with the obvious result!!!!
Ian.

Thanks Ian,
The whole situation is certainly a learning curve!!
My head has also been skimmed to its limits and runs a similar head gasket to yours. The engine has a 700cc kit fitted of unknown origin and my mechanic has advised not to re-use the original performance con rods as they were the only thing holding the broken crank in place when the crank snapped so who knows what stresses they have been put through. There was also uneven wear on the shells (possibly caused after the crank sheared). I'm struggling to find new 'uprated' rods so I have purchased a standard set of 126 rods, which I believe have 118mm centres. I've now sourced a BIS crank as the general consensus seems to be that its a stronger crank. I will compare the throw against my original crank once it arrives