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Sparknotes, I had a machine shop fabricate some spacers to adapt a RB25/RB26 flywheel to a L series.
The basic premise of it, is the back of the L crank is 80mm, the back of a RB crank is 81mm, so there is a 1mm difference that needs to be accounted for. The flywheel bolts will not hold it, they will eventually shear as they are not designed to take the load.
So the spacer I have designed will fix this and allow you to bolt on a RB flywheel, and use a 350z clutch.
We used a XTD brand clutch, which the pressure plate seems to be thicker than some of your name brand clutches, so it rubbed the bell housing. We are using a 280zx transmission (FS571W-B), I have not clearance tested a T5 bell housing yet, but I will very shortly and update the thread.
Other members on hybridz.org have used Exedy, Clutchmasters, with no rubbing problems, so I'm hoping it is just isolated to XTD brands.
The lightweight RB flywheel is significantly cheaper than a Fidanza flywheel for the L series.
You can opt to use a 350z clutch if you want to take advantage of the extra surface area and extra clamping force
Or if you want to stick with your turbo clutch, you can still use a turbo (240mm) clutch, the only difference obviously is the surface area used on the flywheel. But i did confirm a 240mm pressure plate WILL in fact slide on the dowel pins and bolt up to the RB flywheel. This is great if you just want a light weight flywheel but already have a performance turbo clutch, or want to keep the stock clutch, you can bolt it to the 250mm flywheel and only use 240mm of surface area.
This spacer is $30 shipped anywhere in the Continental US. I will ship international, it will just cost more.
I had a very limited run made by the machine shop, so if I run out, I will have to have another order made, which will usually take 2 weeks or so.
Pictures of the bell housing areas are provided in the hybridz.org link above, measurements will be provided in the coming weeks as I have a transmission to pull back out to install this spacer, so I will take more pics and post them then.
Pics of the spacer
Last edited by 83turbo280zx; 04-22-2016 at 08:56 AM.
Updated, I have confirmed you can in fact use a stock turbo (240mm) or performance clutch if you wish to keep the clutch that was originally intended for the car, or don't want to potentially have to grind your bell housing.
I did put a 240mm pressure plate and it slid on the dowel pins and lined up and everything
I have been through a few different machine shops trying to get these things made again, I have been out of them for a few months as my old machine shop went out of business. Currently in development with a new one, hoping to have something maybe by the end of the month.
I do have some further research. It appears as stated above that the RB flywheel/350z clutch clears the T5 transmission without having to clearance the inside of the bellhousing.
As far as non T5 transmissions go, I have found a solution. The RB26 is a 250mm surface area, and holds just as much power as the 350z clutch, and DOES NOT require bell housing clearancing to fit. I have verified this on my personal Z car.
Another minor issue I have come across, I was told by a reputable source that the RB flywheel has an additional 1mm offset towards the front of the transmission compared to the L flywheel. I have not been able to verify this with any precise measuring equipment, HOWEVER, the gear mesh pattern on the ring gear shows the starter to be running about 1mm too shallow, which could possibly contribute to pre-mature ring gear wear.
I just recently finished my engine build, and took the engine/transmission shield and lapped off the area where the starter mounts. It is approximately 1mm thick.
I would advise any future purchasers of the spacer make this same modification to allow for better starter ring gear engagement.
Anyways, here are some pics. I came across a chrome-moly 10lb RB flywheel, and coupled it with a Stage 4 Clutch for grins. We'll see how it does when trying to hold together E85 and big turbo :P
04-18-2016, 02:24 PM
