Machining Clutches for full shift out?

H

Harvey

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Jan 25, 2004
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327
Location
upstate NY
I have heard guys talk of doing this for full shift out,what is involved in doing it and what do you gain,also who does this service?thanks-Harvey
 

you must machine a couple thousandths off of your stock helix. We do this however this is only half of what you must do to gain full shift, you must also buy a overdrive sheeve. We sell this too, this will allow you to reach full shift, much better performance and top end
 
I all ready have a dalton helix which is machined for full shift out,I also have a hauck over drive sheave.I heard guys say they had their clutches themselfs machined.I was wondering what the were talking about.thanks-Harvey
 
Harvey, dont do it, the sheaves will crack over time, because of the heat, they are not that thick to begin with. The gain for the money spent is not worth it. The overdrive sheaves are junk, they are a differnt angle to drive the belt up further in the primary, but your stock moveable sheave is yet another angle, I dont think I want 2 differnt angles on my belt, plus, you must move the engine center to center or they like to blow the belts at wide open, stay away from this stuff, you have the right helix, just tune the clutch's from here.
 
would you believe a shop up here takes the belt off starts the moter and holds a grinder too the bottom inside of the sheves taking off metal that will let them close more. i have heard a brake roter grinder will work or any lathe will but only grind the bottoms as was mentioned or cracks will follow.
 
we just machined my helix the other day for the full shift out and i have our overdrive in it to, I am hoping to get better results then last year. Last year I only had our overdrive and it wouldn't fully go up so I will have to see if machining the helix finished it off. should run pretty good this year.
 
I had mine done locally and its been fine for years and years...maybe my clutching is just sooo good that I don't build any heat in the primary to crack it :)...lol
 
yamiman, i went to a 1.25 track at the same time, but i can tell you i didnt loose any speed once i switched to the 1.25 track. so i was happy because i was told i would loose around 5mph with that track. So i think it worked like they said. I would do it again.
 
I bet if you would have kept all else the same, it wouldnt have done much of anything to help, this mod is a waste of time for about 99 percent of the guys here! your clutch is even more inefficent up in overdrive, plus most guys dont have the proper clutching/springs/gearing to even notice 1 bit of help from this, youd gain more from tuning a straight shift curve and having the chasiss set up to have the least amount of rolling resistance. For argument sake, lets just say your sled goes 120mph flat out, if you cut the clutch and dont change anything else its gonna now go 130mph, wont do it, no way, no how!!!!! when you move the belt up higher in the primary, it also requires other factors to be of gain, like you better have enuff power to keep it there, the secondary clutch spring and helix will have all kinds of effects on this, because the engine will provide less torq. up here and secondary will begin to backshift. Plus, your bending the belt at a very tight radius at the bottom of the secondary, and most likely you will get belt slip there. Theres a whole lot more than cutting the sheaves and sayin "wow' its fast now.....lol! Guys always want a quick thing to do thats gonna be huge gains, when all they need to do is spend some time understanding what each componet does and how it will affect the result by changing it. Tuning the clutch to maximum effiency= less slip=more grip=faster sled!!!!
 
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Yes, good post, but I have to disagree (personally) in some things, I have the overdrive shieve and have lots of power, I geared and clutched mine to work with the shieve in that i can drag race it and it barely reaches the overdrive at the finish line, so i get good top end, but most of the race is not in overdrive, when i lake race or trial ride now i still get over 100MPH but for drag racing i get great acceleration and with the roller secondary i get good backshifting in the deep stuff with the very stiff secondary spring, but like you say you have to make it work, you need to play with gearing and clutching, I use heavy hitters tuned for a straight 8600 RPM shift out..........
 
mrviper, i agree with you in you cant just do the primary shave and be done with it, i also geared down one tooth and changed the helix to a lower finish angle. My plan was going to a 1.25 lug and not loosiing any topend. Actually what i got was a quicker hole shot because of gearing, traction and hc's, with a equal or a little faster topend. So in my mind the shaved primary worked. but again this is just my opinion, i am by far a clutching guru and learn from more experienced guys on this board.
 
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