998 crank differences
Turbo Mini Forums

Looking at what crank to use

the big ends are the same size on A & A+ engines, but what about the mains?

whats generally regarded as the strongest 998 crank? were the 998 cooper cranks en40? or was that just the 1275 coopers?

contemplating just using hardening the std crank and using that, im presuming that ill need to grind the bearings undersize after the hardening process or will a polish suffice?

also, regarding main bearings, am i right in thinking all A+ main bearings have the desirable solid lower shell? the std ones i took out had this, and i cant see different part numbers on minispares?

cheers

joe

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I really do not think that any of the production cranks are different. I think that the A crank will fit an A+ block and vice versa.

Mains and big end bearings are the same size.

As for mains bearings, the A+ block uses the solid bottom half mains with the centre tang, well at least the later ones do.

Problem is that these are becoming rare. The best main bearings are number VP91885, but I cannot find any. I've got the inferior AEM3427s for now.

If you find any VP91885s let me know.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

righto, cheers paul

if i get the crank hardened or cryo treated, im guessing the journals will need to be regroud, at the moment, the journals are in std and in top nick, and i was hoping to keep them that way...

would a polish be able to bring them back without need for a regrind? or is it a suck it and see situation?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

For the 998 Turbo, I just balanced the crank and stuck it back together with new bearings. The journals were in tip top condition.

No need to harden the 998 crank unless you are going very high revs.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Im in similar 'about to put crank in' situation, journals okay, but need to clean off oil stain from centre part where there is no bearing surface on the crentre main..
Any tips??

I don't understand this. There is no bearing surface on the centre main. It's steel.

I guess he means the area where the groove in the bearing are on the centre main. This can sometimes leave a "discoloured" area. This can be cleaned of with a light polish if needed..

Apologies, yeah thats it mini, the part of the journal untouched by the bearing because it has a huge groove in it. Wana clean it before reassembly, you say polish but i dont want to damage the surface! How do i ''light polish if needed'' ?? lol

Seriously, you get a decent machine shop to do it. They will also determine if the crank needs a regrind.

No thank you, mic'd and within tolerance, I have more important things to spend my money on, Only pondering if a little scrubbing with something non-abrasive will work/ has been done before??

If you can, use a LONG strip of 800 abrasive paper and plish the journals. I do this in a lathe to get the crank revolving at the same time. Great care is needed.

WHat use abrasive?
Someone as work suggested using the BACK of a piece like you say, i dont want to remove any metal, or are you sure this will work man ??
Appologies for hijacking joey dude..

Even a bit of metal polish will probably work(Solvol or similar) but unless you can feel anything there as opposed to seing it, why bother ?.

dood If it has a huge grove in it, that indicates that that bearing has worn into the crank which would need a regrind befour building the engine.

no its just oil stained maan

Why not just polish them up with a bit of 600grit wet'n'dry??? thats what the 'professionals' do anyway.

Ive seen peopel do it with a shoelace wrapped around the paper so you get an even finish

I've polisheup mine with Long strip of 1200 wet and dry with some oil on.
One point either polish in both directions (back and forth) or in the direction of rotation. OR else you will eat bearings for lunch...dinner and probably tea!!