The Cal-look Lounge

Hello,
i`ve got a technical question: does anybody knows why there are two different thicknisses of a black magic cluch-disk?
Whitch one do i need?! Has anybody an idea? CSP has them in 6.4 and 8.5 mm thickness.

It has to work with a stage one pressure plate and an scat chromoly flyweel. Engine is 82x94 T1 with idas and dual-quite. Heads
are street-ellis/42-38mm valves. Cam is W140, Witzemanns, Magnum Straigts, Output on dyno: 187hp

i had massiv problems with the berg clutch, hope it will be better with the black magic.

Dirk

Hi Dirk,
What kind of problems did you have? I heard there was a new lighter black magic available, but I dont know if its thinner...

the problem with the berg was it sliped through.....

ok, witch one do i need? 6.4 or 8.5 mm? any idea?

Thicker one,the thin one is for use in a floater style set up,cheers richie,uk

Thank you.

i hope you have better luck with the BM than i did. its not street frendliy or drag frenidly for that matter. im not complaning on how it grabs that part is bittchen. its trying to shift the thing when the rpms are up good luck. and im easy on my stuff compaierd to some. my engine dosent even turn any serious rpm. i like the consept of the BM espealy they way it works on the staring line. yes it is heavier than your normal disk im undesided is this the problem the (wight) or is it that the pads expand so much that when you depress the pedal and try for the next gear you end up grinding a pound of brass and gear. i would like to go back with the disc if i could. last year when i raced at irwin dale last june i was lucky that i made the passes that i did when i ran the 7.82 at88 that pass was ok but after that i had a very hard time second wasent there any more. could have gone way qwiker that night the 60ftwas way better on the last pass that i made but i could not for the life of me get second that was so frustrating >:( even thoe yes i won the event ok thats fine but i wanted to back that up with even a better time. i run the old cush loc now i ran thoes 25 years ago and never had a problem. maybe some of you have some ideas they can share on the BM dont get me wrong i do like the disc we just need to refine it a littel better.  my two bits. UD. ;)

Your sycros will hate you  :o

I've had the worst 60ft's I've ever had with a BM with my 200HP+ pumpgas street car. The grip was so hard it bogged in 1st then wheelied hard. My trans r/p and sycros were thrashed with that setup. Oddly enough I NEVER had a problem with my Ace Copperhead clutch disk with same exact driving style.

187HP engine does not need a BM. A super diakin, Centerforce, Ace copperhead and many other disks will be much easier on the trans and light so it'll be kind to your syncros.  Those disks will slip a tad to reduce shockload to your transmission.

I agree. And it is also a lot cheaper.

A very "in your face" comparison of weight is to hold a BM in your and then a different clutch (daiken superdisc, copperhead, centerforce etc) 

The mere weight of the BM will keep the momentum "spin" of the input shaft of the trans when you dis engage the clutch (step on pedal). This make is much more difficult for the sycros to speed up the next consecutive gear because the input shaft will keep on spinning fast compared to a lighter disk.

Pro-ring is the only way to go with a BM traditional clutch setup IMO.

i do understand what you are saying alan. but when i first put the BM disc in it actualy work prettygood then it got progessivly worse very fast. i understand about the wight factor versis a lighter disc. like you said its a race disc only (proring) the way its set up right now. my sncroys were dust also. but i think it still has a chance it needs to be re enginneered for a sncroy box. ive heard some people having good luck with them. but ihave heard more bad. the good ones are probely not leting us know that there boxes are proringed. some more of my two bits. UD. ;)