Expert: Dan Liddy - 10/10/2009

Question
Hi Dan, I read an article you wrote about performance improvements on the Datsun/Nssan 280ZX. It was interesting reading and you seem to have good knowledge. I plan to lighten the flywheel on my car (2+2, thus 240mm steel flywheel) by about 10lbs and was wandering about your comment (put a 'step' in the clutch mounting surface so that the pressure plate sits closer by about .025"). I plan to keep the stock clutch and pressure plate - only for street use, I'm not making any serious mods or race the car. Just want slightly better acceleration. Would any shop experienced with lightening flywheels understand what is meant if I ask then to put a step in the mounting service? Perhaps it will help me if you can explain a little bit more in detail what a step is. (I am not technical at all when it comes to flywheel and clutches)Thanks

Answer
Hi Gerrit:
I don't usually take questions about street cars, but since it's about my true love, the "Z" car, I'll give in.

The flywheel as stock weighs nearly 30 Lbs.  You can lighten it to about 15-16 Lb. Here's how.
First off, on the front side,(toward the engine) you'll see a wide area of thick metal around the outside edge, about 2 1/2 " to 3" wide.  You can have this trimmed until there is only about 1/4" left of that area, just enough to hold the ring gear for the starter. Your machinest can cut it to the depth of the rest of the wheel measured in the middle.  Since it's on the outside there is quite a benefit, sinc eyou are removing weight that creates lots of inertia.

AS for the step process, if you will look at the clutch mounting surface, you'll see that there are two faces, one for the clutch disc which needs to be resurfaced, and then a grove, and then the outside mounting surfce for the clutch pressure plate.  That mounting surface can be machined (stepped) down another .025" to increase the pressure of the pressure plate on the driven disc.
Write to me at <DNLDDY@AOL.com> and I'll try to make you a drawing which will help explain it.
I'm not good at the drawing program but what I've done might help. do write !



Good luck,


Dan Liddy
Sarasota, Florida.