So according to several links on twinturbo.net, and a few on here as well, the TT flywheel should have a 0.008" step up for the clutch contact surface. However machine shops and Exedy (yes I called their tech dept) swear black and blue that 'almost' all Nissan flywheels are flat with no step, including the 300ZX TT. Has anyone ever checked on a brand new factory OEM flywheel if there is in fact a step? What about on an aftermarket lighted flywheel? ie Jun, Fidanza etc? Does anyone know if it's actually referenced anywhere in any official Nissan documentation? From what I've researched most of the time in Aus they are machined flat, and it doesn't seem to cause too much issue. Of course if they are supposed to have a step, and they're machined flat, the clutch plate has to travel that little bit further before it makes contact with the flywheel though.
I was always under the impression that the TT flywheels had the step and the NA's did not. I've never looked at a TT flywheel too closely to be honest. I agree that it's not going to make a whole lot of difference if the step is machined off. 0.2mm is not a lot especially compared to the expected wear on the clutch friction disc. Have you looked at the service manual for specs?
So being that Exedy claimed they are 'definitely' flat, you would assume their clutch kits have been engineered on the basis that the flywheel is flat, so I had mine machined flat as I'm using an Exedy cushion button clutch. Problem is, when I checked it once I got it home, it wasn't actually flat!! From the centre edge to the outside edge was a 7-10thou drop! Somehow they'd managed to machine it on an upward incline to the centre! Worse, I bolted it to the engine to check runout, and the freshly machined flywheel had around 10thou runout, almost double the Nissan acceptable maximum of 6thou! Not happy. So took it back today straight to the owner. To their credit they checked it, confirmed it was wrong, re machined it, checked it again, and gave me a refund (not that the refund really made up for the 4-5 hours I'd wasted due to their poor machining). Anyway so it's now perfectly flat, and with only around 3-4thou runout (would have preferred closer to zero but). Always check anything you get machined peoples! I'm amazed at how many machine shops in Sydney can't machine a flat true surface for shit!! And take pictures before and after in case you have to prove their mistake, or shame them on Facebook lol!
Re: So according to several links on twinturbo.net, and a few on here as well, the TT flywheel should have a 0.008" step up for the clutch contact surface. 0.008" is not a step of any significance. Anyway so it's now perfectly flat, and with only around 3-4thou run out (would have preferred closer to zero but). The above sentence seems to contradict itself..............
I recently changed the clutch in the "Ute Of Death" and i use a TT clutch assembly. Extreme assured me that their clutches dont have a step. My old Pulsar turbo ET engines definitely had a step tho. Many guys had clutch slippage issues with quite modest power and I suspect that a lot of flywheels were machined flat as a matter of course with a clutch built for a step. Regardless of step, or no step, the clutch assembly should be bolted down and the height of the diaphragm fingers measured. This data will be courtesy of the clutch manufacturer, NOT the manual. The manual info is peculiar to OEM clutches only. Depending on the clamp of the clutch and the diaphragm characteristics, this measurement can be critical to the correct clamping and throwout of the clutch over its working life.
East Coast, when you're talking mm's, 8thou is significant. Exedy were adamant that using their clutch with a step would result in excessive clutch wear. Also having a flat surface with runout is not contradictory, think about it
