8 replies to this topic

[Goacher65]

Question for anyone who may be able to help.

 

I am looking at the possibility of doing some form of crossflow conversion to my clubby. Options looking at 8 port of BMW K-series 16v conversion. Would like 120/30+ HP comfortably. Car is used as a toy (weekends/trackdays). 

 

My current 1380 has a CAM 6581 crank in it (std/std bearings still). There are number of unknowns with these cranks as to what exactly was done to them when manufactured. Not sure if they're EN40B/16T, but that whatever they are and treatment, they're pretty hard wearing. 

Does anyone know if in their standard form, they're capable of high rpm? Both the BMW 16v and the Arden head would probably be looking at high RPM for the sort of power I'm looking at, and if I ever wanted to get more power, would be nice to not need all new components.

 

Two questions I guess:

1) Are they suitable for sustained high RPM, 

2) If I was going to modify it (lighten/wedge/blade), would it compromise whatever the treatment of the crank is?

 

Would something as simple as cross-drilling compromise the standard casting in any way?

 

Thanks, in advance, H.

[mini13]

Cracking crank, not strong as such, but as you say due to the hardening really wear resistant, they are 16t, and once they get through the hardening wear fairly fast, well the same as std Cranks anyway.

K1200 head and cams should net you 130 hp, and that crank will stand up to it,

[mini13]

Also don't worry about moding inyroducing issues, the hardening is really for the journals for wear resistance,

Edited by mini13, 29 December 2017 - 11:18 PM.

[Spider]

They are basically a pretty good and reasonably 'strong' crank out of the box, though in that casting number, there a few incarnations of it - the standard version and that fitted to the Metro Turbo. Both are EN16T but the latter was Tuftrided.

 

For your proposed Project, I would suggest Wedging the Webs on the Crank, having it ground & indexed at the same time and of course, finely balanced. When having the crank ground, I'd suggest using bearing clearances of 0.002" as a minimum and on the crank thrusts a minimum of 0.005"

 

You also want to look and and carefully consider all the parts you'll be screwing on to the crank, as they will have much more bearing on it's life than the crank itself, in particular, the damper. If you are going down the BMW K1100 Head route, from memory, because of the Camshafts used, the firing order is different (IIRC the BMW Engine spins the opposite way to the A Series) and this will introduce a different range of Harmonics which the stock damper is unlikely to cope with.

[Goacher65]

They are basically a pretty good and reasonably 'strong' crank out of the box, though in that casting number, there a few incarnations of it - the standard version and that fitted to the Metro Turbo. Both are EN16T but the latter was Tuftrided.

I believe this to have been from a Metro Turbo engine, though I can't guarantee this, are there further serial numbers to look out for that might clarify this?

 

Also, in relation to the journals. If the journals are still OK, is it wise to regrind the crank as a matter of course, or is this going to compromise the hardening (turftriding/nitriding). Not sure what the difference is, but am I right in saying one goes deeper into the casting than the other?

 

Regards, H

[Goacher65]

Cracking crank

Not literally, I hope!

[mini13]

Lol!

[Spider]

 

I believe this to have been from a Metro Turbo engine, though I can't guarantee this, are there further serial numbers to look out for that might clarify this?

 

Also, in relation to the journals. If the journals are still OK, is it wise to regrind the crank as a matter of course, or is this going to compromise the hardening (turftriding/nitriding). Not sure what the difference is, but am I right in saying one goes deeper into the casting than the other?

 

Regards, H

 

 

Regrettably, it's quite difficult to ID the Tuftrided Crank from the untreated, a lick with a file is one way - if you know how the harder and softer cranks should feel. A File should skim over a Tuftrided Crank (unless you lay in to it) but will mark a stock one. You need to do this test on the journals though and that will obviously mean it will need a grind after this.

 

At 0.010" they don't need retreating, however, at 0.020" it will need retreating.

 

Given the type of engine you are building, at the very least, I would check the stroke of each journal and each journal's index, seldom are they right, though some closer than others. If these are out, more than you're comfortable with, then even if the journals size & shape are OK, a grind is the only way this can be corrected.

 

You also touched on cross drilling. I'm not a fan of doing it I have to say, but fitting some screw type restrictors could be wise - if and only if - you'll be sitting on high RPM for extended periods with not a great deal of low RPMs. Although I'm not a fan of cross drilling cranks, these should be OK with it, but seek further advise.

[Goacher65]

Brilliant, you've both been very helpful!

 

I'm not a million miles away from Bill Richards, so he's probably a good man to speak to and see if/how far it's worth going with the crank vs. getting a new forged item. Just seems a shame if I could get the use out of this with some simple modification, to spend 1-2k on a replacement crank (Will make the conversion much more affordable too!). He's always been good with me in the past, and will likely tell me if it's not worth doing!

 

Regards, H