Dave@SBClutch

hey, I know a guy with good parts..... lol.

You may want to try a higher quality one. I'm not 100%, but maybe their chinese knock off slaves are made with inferior materials. Also, you may want to look at your clutch. I know that as a clutch wears out, it may become stiffer. If you happen to go this route, and the disk thickness is good. Blow the pressure plate out well with compressed air. Sometimes clutch facing dust can bind the mechanism. FYI, it's generally standard that a clutch disk will measure about .308 thick. That's with all the marcel squished down (the spring between the facings).

My book says the changes started in September of 1986. Hope that helps.

Jason at Z31parts.com offers poly bushings, lowering springs, adjustable cam gears, fuel rails, clutches and flywheels, etc. Joe at Zspeedperformance.com offers aluminum splash shields, stainless clutch hoses, clutches and flywheels, etc.

safety?

Thanks, this little diesel rev's to 5,500 rpms and we launch at 85psi. It's kinda a get it and hold on, kinda thing

This is our race car. There are three of us who drive this, the video is of my teammate Manseil. The chassis is a 76 CJ5 stretched 18 inches. The body is a 32 Ford vicky 5 window. The engine is a Cummins 4BT (4cyl) diesel. We've twin turbo'd it and we're spraying the equivalent of a 275 shot of nitrous. Putting down about 800hp and 1500 lbs of torque. Tires are 44" cut boggers. We built a diesel bogger because 80% of our business is diesel. It Features our adjustable hydraulics and twin disk clutch. mudrail.MOV

John, I think it's a simple as following the torque curve. Lets use this as an example. If you're power band is aprox. 3-6000 rpm, and your peak torque is 5000. To shift from 5800 and drop down to 3800, you're further away from peak torque. If you could get a bit closer, lets say.. 4100rpm. You're staying closer to your peak torque and peak HP. More power to the ground = faster ET's. Again, it's RPM fall off. If you'd like to know the reasons we don't like aluminum flywheels, we see issues with aluminum flywheels too often. We see guys stripping out pressure plate bolt holes partially when assembling the unit and not knowing it. We see clutches coming off the flywheels. We also see the trend of aluminum flywheels is going away. It's moving twords lightened steel. The other problem I see is the hardened steel insert in the aluminum flywheel is not machined after being bolted in. If you were to grind the insert, you see aprox .004 low spots around the bolts holding it in. Creating an uneven surface, not allowing full disk contact. Aluminum has different expansion and contraction rates then steel. The relationship of the insert to the pressure plate mounting bolts allows the thickness of where the disk rides to change with heat. Where it would be more gradual with a one piece steel flywheel. .010 of change in disk thickness makes about .070 of change where the bearing rides at the end of the diaphragm spring. Not to mention heat can cause the insert to curl (soup bowl) causing a non release issue. Jon, I haven't driven a straight 6 with an aluminum flywheel. It may not be too bad, just as a 4 puck on a honda civic isn't terrible. Not all cars act the same with certain parts. I understand that and maybe I spoke out of turn. But general knowledge in my industry is that drag racing times are better with heavier flywheels. It's seen a lot in boosted cars with big turbos falling out of boost. As far as durability is concerned. There are two fulcrum points inside of a pressure plate. One on the inside of the lid and one on the casting. The diaphragm spring does wear the cast iron with miles. Aluminim would wear faster with a piece of spring steel riding on it.

The main reason for the sprung center of the disk is transmission wear. Without dampening, metal slapping on metal wears quickly. Even if it's hardened. Glad to hear you guys have been happy with my products. I think I'm going to try to bring better aftermarket support to the 240/260/280 market. We already have a big Z31/32/33/34 market base. Including a car with 850rwhp on one of our single disk clutches. Not to mention dozens of 6-700 hp cars.

How new is your flywheel? If it's been resurfaced too many times, it would move the entire clutch assembly away from the bearing. Could be related to your issue.

I personally am not a fan of aluminum anything on the drivetrain unless it's a dedicated autocross car. You're absolutely correct that eliminating all the rotating mass will make it more difficult to drive. Yes, your engine will rev faster. But it'll drop nearly as fast. Which is why most guys who run them end up turning up their idle so their car doesn't stall. Infact, we see better 1/4 mile times with heavier flywheels on cars because it keeps them in the power band. Especially on boosted cars.