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CONFIRMED L28 with RB25 Flywheel and 350Z Clutch


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UPDATED 07/29/17 ** RB26 flywheel to L-series Crank Adapter for sale - $40 shipped continental US. Information below**

 

Ok, we finally got the flywheel adapter made from the machine shop. As discussed below thanks to Xkne, I had one made.

The back of the crankshaft OD on the L series is 80mm, the OD on the back of a RB crank is 81mm, so there is ~1mm of difference. This spacer will take up the slack so you can do this job right and not shear flywheel bolts in the future.

 

This spacer has a slight taper to allow it to bottom out against the back of the L crank against the chamfered edge, and then you bolt on your RB flywheel and tighten it down.

 

The entire purpose of this is to get a significantly cheaper chrome-moly light flywheel (14lbs) to use on the L series rather than the more expensive Fidanza flywheel. On top of this, you also get a 250mm surface area vs. a 240mm surface area.

 

You can either opt to use a 350z clutch, which has amazing 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.

 

The fidanza flywheel for the L28 costs $330~

The XTD flywheel for the RB25/RB26 costs $162~

 

This spacer will cost $40 shipped if you're in the Continental US. WILL SHIP INTERNATIONAL, it will just cost a little more.

 

For information and ordering for the spacer, e-mail me @ sk84life1122@sbcglobal.net

 

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Ok, working on a 240z with a L28ET swap. We did a XTD 15lb RB20/RB25 flywheel with a 250mm surface, we also sourced a XTD 350z clutch.

 

We are also using a close ratio FS571W-B 5 speed from a 280z.

 

I've read a few different threads where people have done this, but no definitive answers as to if it is direct bolt in, or any lingering modifications had to be done, but here is what our experience was.

 

Not sure if name brands like Exedy or Clutch Masters would fit different, but I've been using Gripforce, F1 Racing, XTD clutches for years with ZERO issues, I think a lot of the negativity stems from improper installation.

 

Anywho, we did have to grind away some material on the inside of the bell housing.

 

The transmission bolts up, slides in and everything, you wouldn't think there would be any issues at all, it bottomed out against the dowel pins in the block.

 

When we went to start it the first time, the non-gear reduction starter just clicked, like the motor was locked. It was faster for us to swap to a spare gear reduction starter, rather than remove the radiator and fans to get access to the crank bolt, It's a tight fit on this non-stock build lol.

 

So with the gear reduction starter it cranked, but fairly slow. So we pulled the starter and saw some fresh metal shavings.

 

Pictures will be as follows, nice clutch cover line around the majority of the perimeter of the bell housing.

 

Not sure if because it's an earlier 5 speed that the bell housing casting was a little tighter than the later ZX trannies, or if the clutch cover was a little out of tolerance, but it rubbed enough to slow the cranking down. So we "clearanced" the bell housing to allow the clutch to move freely and now it cranks fine and works like a charm.

I would definitely recommend this upgrade, because this flywheel is ALOT cheaper than the L28 fidanza flywheel, and you get an extra 10mm of surface area, PLUS you get the clamping force of the 350z clutch, this thing will hold more power than this engine will ever see.

 

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Definitely not for the feint of heart, but a 4" angle grinder did the trick in about 5 minutes to grind about 1-2mm of material out of the way to clear the clutch cover.

Edited by 83turbo280zx
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Very cool.  Thanks for sharing!  I am always interested in what parts from other cars can be directly swapped into the S30.  The grinding to the bell housing doesnt quite make it as a "direct swap", but that amount of modification is negligible enough that I would still count it as "bolt in".  

 

How is the clutch feel on the 350Z unit?  My stock 280Z unit is insanely easy to press (not sure if that is normal or if mine is just starting to feel the years).  Just wondering how much stiffer the 350Z unit makes it.

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Very cool.  Thanks for sharing!  I am always interested in what parts from other cars can be directly swapped into the S30.  The grinding to the bell housing doesnt quite make it as a "direct swap", but that amount of modification is negligible enough that I would still count it as "bolt in".  

 

How is the clutch feel on the 350Z unit?  My stock 280Z unit is insanely easy to press (not sure if that is normal or if mine is just starting to feel the years).  Just wondering how much stiffer the 350Z unit makes it.

 

Yea, it's not much material that has to come off, the best way to mark it would be bolt the transmission up and turn it over a couple of revolutions to "bed" the bell housing, then pull it back off and grind in the marked areas.

 

I bought a $20 electric angle grinder from harbor freight, did the trick in about 5 minutes lol.

 

The clutch is a stage 2 and it is definitely a stiffer pedal feel than a stage 2 280zx turbo clutch. But i'm hoping once it gets broken in and used a little bit it will lighten up. it's not unbearable by any means. It still has the damper springs in the clutch plate so it won't be on/off feel like a stage 4 solid clutch plate.

 

I've driven cable clutches with a stage 4 and you wanna talk about a leg and ankle workout lol.

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It's a shame you didn't measure that mark from the bell housing flange so we could have a reference

If you look at the picture where the clutch slave bolts are in the bell housing, you can use that for a reference, grind down 1/2" to 3/4" on each side of the bolt, and work around. Or just bolt the trans up with 2 bolts, bolt your starter up and crank the engine a couple of times, remove trans again and see where it hit.

 

I'm running a FS571W-C with a "B" bell housing, so when I do this conversion with my motor build, i'll actually measure where to grind down. We are on a time crunch trying to get the car ready for Hot Import Nights, so we are moving as fast as we can.

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I feel like I remember hearing something about xtd clutches being physically bigger or thicker than lets say an ACT.  Anybody else hear anything like that? If so a different clutch could solve the issue.

That's what I was thinking. I know its hardened steel, but maybe they used a lesser quality steel versus ACT or somebody with premium metal, so they made it thicker to strengthen it? That's really the only explanation I can think of. Or the offset of the RB25 flywheel is slightly deeper into the bell housing. When I order mine, I'll have to make some measurements of thickness and offset compared to the stock turbo flywheel.

 

I also have a spare T5 bell housing I've been sitting on, so I may bolt it up and see if the T5 rubs, that would be some good information to have for the T5 guys who want a cheaper lightened flywheel and strong clutch

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So, did you fit the shim to the flywheel or are you waiting for it to shear the bolts and come out to eat your feet?

 

The RB flywheel has an 81mm register bore, the L28 crankshaft is 80mm. Needs to have a thin ring pressed in to center the flywheel, otherwise the slightest imbalance will start it moving around and wearing on those flywheel bolts.

 

I believe I posted that information when I did this a few years back.

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So, did you fit the shim to the flywheel or are you waiting for it to shear the bolts and come out to eat your feet?

 

The RB flywheel has an 81mm register bore, the L28 crankshaft is 80mm. Needs to have a thin ring pressed in to center the flywheel, otherwise the slightest imbalance will start it moving around and wearing on those flywheel bolts.

 

I believe I posted that information when I did this a few years back.

 

 

I did notice it was slightly off, but the flywheel bolts I had, had a raised section on the non-threaded portion that fit perfectly in the flywheel holes for the bolts and centered it up. The starter engages properly, no issues there.

 

I saw this quoted on your thread "I ran an RB30 flywheel on an L28 for about 5 years with no problems, that was running it with no shim around the spigot either, just located on the bolts. That was using a late S130 reduction gear starter. Neither the starter or the ring gear showed any signs of damage"

 

If you know a source for spacers that are for this flywheel swap I would greatly appreciate it if you could share. Worst case scenario I'll just have to pull the trans back out and shim it with one I can get made by a local machine shop. The engine is already assembled and running, so it's a little late to dowel the back of the crank.

 

From my experience, I could not feel a flywheel imbalance when driving the vehicle, and thankfully it's a 240z so the bell housing sits a little forward of the firewall, limbs are not in the direct line of fire lol.

 

I will definitely have to look more into this issue, at least its a 240z, we can pull the trans in about 5 minutes in the driveway, probably take longer to put it on stands with it being so low on BC coil overs lol.

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Ok so I ordered a speedi-sleeve for some R&D. The machine shop that machines my L28 bell housings for the KA trans swap might be able to use that as a template to make one that is 1mm thick, but not as deep on the crank so we don't have to contact the rear main. Will keep the thread posted.

 

Might be able to market some for people interested in the RB flywheel swap.

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I made my sleeve. It's 0.020" thick...remember the 1mm difference is diameter, the thickness of the sleeve is radius.

 

The bolts were never designed to hold the shear forces like that. They are meant to clamp the flywheel to the rear of the crank, but they are not meant to be the sole locating force.

 

I think the speedi sleeves are .011 thick

 

I measured the speedi-sleeve and it's 0.25mm thick. I ordered a flywheel for my personal vehicle, have a crankshaft that is already of the engine and in storage, so I will drop off the crank, flywheel, and measurements to the machine shop and have them come up with a sleeve that can be lightly tapped on with a rubber mallet and but up against the chamfered edge of the crank but not interfere with the flywheel spacing or the rear main.

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  • 3 weeks later...

Dropped everything off at the machine shop yesterday, hopefully in a week I will have the first working prototype, if anyone is interested in one of these spacers I will get some pricing per unit once we get a working prototype developed.

 

Even with the spacer, flywheel, and clutch, it's still cheaper than a fidanza flywheel for the L series, and you get a really beefy clutch

 

Also going to test fit on a T5 trans so we can see how it clears versus the FS571wb/c trannies

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The T5 bell is a little tighter than the FS5W71 transmissions, you might need to clearance it a smidge for the pressure plate assembly. Most should clear fine, though.

 

The last few billet steel RB20/RB25 flywheels I did, I just welded the register bore and re-machined to a 80.00mm fit, the cranks I've had here measured 79.95-79.99 on the seating surface.

 

I wouldn't make such a big deal out of the flywheel register being off if it wasn't for the fact that when it comes off, it'll eat your feet. Also, the "mill 6mm off the back of the crank" story that goes around as a "japanese high-power crankshaft" modification is so that they can use unmodified twin clutch RB/KA flywheels, the register surface moves to the inside spigot at 35mm and the 81mm bore isn't used at all.

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The T5 bell is a little tighter than the FS5W71 transmissions, you might need to clearance it a smidge for the pressure plate assembly. Most should clear fine, though.

 

The last few billet steel RB20/RB25 flywheels I did, I just welded the register bore and re-machined to a 80.00mm fit, the cranks I've had here measured 79.95-79.99 on the seating surface.

 

I wouldn't make such a big deal out of the flywheel register being off if it wasn't for the fact that when it comes off, it'll eat your feet. Also, the "mill 6mm off the back of the crank" story that goes around as a "japanese high-power crankshaft" modification is so that they can use unmodified twin clutch RB/KA flywheels, the register surface moves to the inside spigot at 35mm and the 81mm bore isn't used at all.

 

Yea i'm guessing since I had to clearance the 71b bell housing I will have to clearance the T5 bell housing, but anyone who is willing to invest in a $25 electric grinding wheel and 30 minutes of time can do this in their garage.

 

I thought about welding material to the flywheel and re-boring to 80mm, but for bolt on purposes, I feel people would be more inclined to do this swap if the only modification they had to do was removing 1mm of thickness from key points on the bell housing, and using a steel spacer to take up the slack on the crank

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