FDF

Don't skimp when it comes to the clutch if you are planning future power upgrades.If you're going to pull get a good pulling clutch.I tried to save money when I bought mine thinking I was done bombing.I'm now wishing I had put an OFE or a Mitchells.The con-o has done pretty good(drag racing,a couple of pulls,and some dyno runs),but it will slip if I don't watch it.I'm hoping Peter gets his pulling clutch ready soon as I am thinking about doing some more pulls next year...Doug

Rob Thomas

[quote author=ridofpwrstroke link=board=7;threadid=7805;start=0#76612 date=1039196065]<br>How much does the pulling clutch cost? Is it better than a SBC? I am upping the power slowly and the clutch is my next option. Thanks for the info, this is great info.<br>[/quote]<br><br>&quot;The&quot; pulling clutch (Mitchells), is $1700, is it better than a SB? Used for what it was designed for, yes it is, no doubt.<br><br>Later, Rob

Don M

Rob,

How much do they machine off the flywheel to get it all to fit inside the limited area? I was concerned when I first heard this, but still not sure how much it matters. A lighter flywheel seems like a great idea in principal but I have seen the gassers lose &quot;out of the hole power&quot; from the lower inertia.
I dont think strength would be an issue as long there was not too much removed.



Don~

South Bend Clutch

Don,<br><br>Not to pick on you here but you said earlier that by relocating the holes on the flywheel for the 13&quot; might loose it's integraty and now you don't see how cutting any where from a 1/2&quot; to 3/4&quot; out of a flywheel that is 1 1/2&quot; thick would. ???<br><br>The Mitchell clutch requires modification to the fork and bellhousing for it to fit.<br><br>Peter

oldred97

I was gonna question that too Peter but didn't want to start anything.

Don M

Hi Peter,<br><br>I asked how much was cut off to help me make that determination. I stated I &quot;did not think&quot; it would hurt anything, but I really did not know how much they machined away, so I asked. I did not know they cut away that much material though. <br>The difference of a 1/2&quot; to 3/4&quot; is quite a bit. I wonder if anyone knows how much is actually machined away? I do know the OEMs frown on cutting the flywheel down too much.<br><br>On the topic of redrilling a 5 speed flywheel to accept a 13&quot; clutch, I dont like the idea for me. The bolt holes end up very close to the grooved ring for the starter to engage. I would rather see the 13&quot; flywheel stuffed in the 5 speed bellhousing, if it will fit. Of course then I go back to a higher inertia flywheel giving me a higher parasitic drag. Not good IMO.<br><br>Don~<br><br><br><br>

South Bend Clutch

Don,

Think about it this way, the Sach disc is .400&quot; thick (this is done with the gap of the pressure plate) and the stock disc is .310&quot; thick. Now, going to a button disc, you are starting with a drive plate that is .090&quot; and you have to add the buttons to both sides. The thinnest button made is .130&quot; x 2 is .260&quot; + the .090&quot; and you have .350&quot;. Now that is a super thin button. The buttons go from .130&quot; to .140&quot; to .156&quot; to .174&quot; to .186&quot; (this is just how they are made). You wouldn't want to go super thin so let's split the difference. .156 x 2 = .312 + .090(drive plate) = .402&quot;...now you have the disc thicknesses. This is .100&quot; over stock (other then Sach). You have two disc so now you are at lets just say .800&quot;. Your OEM gap is .310&quot; so we are talking of a difference of .500&quot; aprox. Now lets add the center plate, Min. anyone would go on a center plate is .300&quot; should be more but let's go with that for sake of argument. Now we are at .800&quot;. What you then do is cut the pressure plate casting thinner to accomodate some of this thickness. If you go to thin you will loose the integraty of the casting and it will not be able to except the heat that is being made. So let's go with .200 (alot) and we are back to .600&quot;. That is what needs to come out of the flywheel.

I hope this makes sence and helps you to understand how it is done.

Peter

Don M

Yes, it does help. My Sachs disks measures about .375 with the brass ceramic pucks and the iron ones I tried measured about .400
The pressure ring if machined too far will lower the clamp force correct? Or if not machined enough it will have the same effect correct? I did understand that the pressure ring needs some material to maintain some structural integrity from heat, etc. So basically we need to cut about 6-700 thou off the flywheel. With a starting dimension of an 1-1/2&quot; we would cutting the flywheel down to about .850 or so.

Iron weighs about what per square inch? What is the diameter of the flywheel in the ETH and what is the diameter of the entire bolt circle area so I can remove that from the weight?

Don~

edit- I wanted to attach this screen shot from Cummins. The max rpm this flywheel is rated for is 4410rpm. Of course Rob aint gotta worry about exceeding that

Rob Thomas

I'm not 100% sure, but I think the flywheel is machined .110, it's not 1/2&quot; or 3/4&quot;, that I know. <br><br>Also, I installed my Mitchell clutch, I didn't modify the bell housing, or the clutch fork, however it is different on the 5-speeds.<br><br>4410 rpm? Your right Don, I'm safe...................for now. ;D<br><br>Later, Rob

Sled Puller

I think that Peter and Don both would be better off not commenting on technical aspects of a clutch that they know nothing about, and have no intentions of owning one.<br><br>If you are going to pull more than twice in your life or less, get a pulling clutch, or you will be just smoke. Been there.<br><br>Mitchells clutch sled pulls and hot shots, it handles all the power and TQ that anybody on these boards can throw at it on the track, and then haul the gooseneck across the country.<br>It is probably the best buy for the money I have ever made on my truck.

Don M

[quote author=Sled Puller link=board=7;threadid=7805;start=15#76896 date=1039232858]<br>I think that Peter and Don both would be better off not commenting on technical aspects of a clutch that they know nothing about, and have no intentions of owning one.<br><br>If you are going to pull more than twice in your life or less, get a pulling clutch, or you will be just smoke. Been there.<br><br>Mitchells clutch sled pulls and hot shots, it handles all the power and TQ that anybody on these boards can throw at it on the track, and then haul the gooseneck across the country.<br>It is probably the best buy for the money I have ever made on my truck.<br>[/quote]<br><br>With a 557 HP truck, even the SouthBend would hold <br><br>Joking of course Gene. I wanna know more about this pulling clutch you have. Did Dave really machine off over a half inch of your flywheel to get it to fit? Did you feel that might be somewhat unsafe? These cast iron flywheels are great but once you machine away nearly half the bulk I would not be surprised if cracking would be a problem. Further, once a crack begins its not long before an explosion can occur. Chunks of flying cast iron flywheel is not funny. Even if it happened to you <br><br>Don~

Sled Puller

[quote author=Don M link=board=7;threadid=7805;start=15#76909 date=1039234558]<br><br><br>With a 557 HP truck, even the SouthBend would hold <br><br>Peter? Want to donate a clutch for this scientific test?<br><br> Did Dave really machine off over a half inch of your flywheel to get it to fit? <br><br>Don~<br>[/quote]<br><br>No, Dave did not machine a half inch of material away to get it to fit.<br>That is a rumor started by some competitors to try to hurt Mitchells sales, because their own clutches were failing at an alarming rate, and they were getting disgrunlted that their neighbors were driving hours away to get a good clutch.<br><br>The ploy didn't work, though. I guess that is a sign that you have a good product, or you have reached the top of your field. When the competitors just bash your products instead of trying to build a better one.

Don M

Sled,<br><br>How much did he machine off? How do all the disks fit in the bellhousing? Going by Peters measurements it appears a fair amount would have to go somewhere. Maybe that 1000HP engine of Daves is just directly connected to the transmission with a jackshaft..NOT!!!! ;D<br><br>Don~<br><br>

Rob Thomas

[quote author=Rob Thomas link=board=7;threadid=7805;start=15#76882 date=1039230864]<br>I'm not 100% sure, but I think the flywheel is machined .110, it's not 1/2&quot; or 3/4&quot;, that I know. <br><br>Also, I installed my Mitchell clutch, I didn't modify the bell housing, or the clutch fork, however it is different on the 5-speeds.<br><br>4410 rpm? Your right Don, I'm safe...................for now. ;D<br><br>Later, Rob<br>[/quote]<br><br><br>Don,<br><br> I had to quote myself, cuase apparently you missed it the first time.<br><br>Later, Rob

South Bend Clutch

Guy's,

Please don't misinterpret what my earlier post stated. (beauty of the internet) I was only pointing out that Don was contradicting himself saying that redrilling a flywheel for a larger clutch would hurt the integrity of it and he didn't think cutting a flywheel to fit a double disc would. I KNOW that redrilling will not as much as I know (if properly done) cutting the flywheel will not. This is what I do for a living. Now, as to what it takes to put a double disc 13&quot; clutch on the original flywheel? Again, this is my business and I know what is available in the clutch world to make the components. You may not want to tangle with me on this one. Trust me, I am not baffled and it is not a mystery to me. Gene, we have talked and you know why I did not run right out and offer a double disc pulling clutch, it is not because I don't know how to build one. Enough said.

Peter