11 replies to this topic

[mniguy_nz]

Hi Guys,

I'm sure plenty of you have had cranks nitrided and the Cooper S came standard but does it increase wear life a lot? Every
standard crank I've removed with decent km's has needed a regrind and I'd like to avoid regrinding next time round. My engine
builder said most Jappas are nitrided standard and never need regrinding.

Also do I just drill the oil galley plugs out to clean the oil galley?


Cheers

Tim

[MRA]

What wear (no pun intended) are you seeing..... if for instance you get more on the centre main bearing then I would suggest cross drilling and tuftriding, the correct tuftriding process gives a tougher, harder crank which is less prone to fatigue failure, whilst also decreasing the uF or COF (coefficient of Friction) so in this instance it could help a lot.

However if you are using prolonged high (6000rpm) rev or above then cross drilling would be more beneficial to your reliability

Both would be even better of course..........

[bmcecosse]

You can only 'nitride' a crank made from suitable steel - EN 40B in the case of the S engines. Centre main bearing wear can be caused by a slightly bent crank - and by out-of-balance flywheel.

Edited by bmcecosse, 18 June 2010 - 08:34 AM.

[MRA]

Yes and all others can have a tuftriding or nitro carburising process often called Ni-temp, which is a low temperature process with good results

[bmcecosse]

Indeed they can - but it ain't 'nitriding' - nor is it as good as real nitriding!

[MRA]

The nitriding is a completely different process to ni-temping, and is not as good because of the base metal, EN40B is a moly steel with excellent resistance to fatigue whilst also being extremely strong, where as ni-temp is performed on lower grade steels to raise them to a higher more durable level which it actually does better than nitriding, this doesn't mean that a nitemp'ed crank is better than an EN40B crank that has been nitrided. it simply means that the gains are of a higher percentage.

[mniguy_nz]

I forgot to mention its a 12G1505 Crank from a morris 1300. The wear is worst on the rear main bearing and then next worst on the centre main. There isn't much on the big ends which I find strange as they're fed but the mains. The company is Heat Treatments and the process is Carbonitriding, described in the following link. Does this sound good for the 1505?

Thanks for the advise, much appreciated

[MRA]

Mains suffer from cavitation and oil starvation caused by the crankshaft spinning and thus generating centripetal forces. Normally the worst hit is the centre main as it feeds 2 big ends.

Yes that is one type of heat treatment that will do the job just fine, you may need to check the crank for distortion, ask them about crank distortion due to heat exposure and what temperature it will be heated to ?

[CraigyBoy]

Anyone know the answer to the oil gallery plug question? I may also need to remove one due to a leak and would like to know.

Thanks

[bmcecosse]

Check if the crank needs to be ground close to size - then hardened - and then finally ground to size. This can add quite a bit to the cost!!!!!!!!

[MRA]

If they are the solid type then yes, if they are the cup type you could use a large coach bolt (wood screw thread) tap it in to the brass cup and screw in then lever the screw and cup out as one

http://mra-minis.co....503-cam4133.htm

[mniguy_nz]

Hey thanks for all the info. Extremely helpful