Lightened flywheel

[landmizzle]

Hi all,

I'm about to begin the process of swapping out the automatic tranny in my 72 240Z with a 5 speed unit from an 82 N/A 280ZX. I'll be keeping the 3:54 rear end in my Z.

Since the tranny will be out I'm considering lightening the flywheel. I've thought about an aluminum one but I think that may be too light and am concerned about the longevity and reliability of it. Does anyone have any suggestions about how much weight can be safetly removed from the stock flywheel.

The car will be used as a daily driver with a good amount of spirited driving. I commute daily 100 miles with a good portion of that commute in twisty hilly areas (fun!!!!!) the majority of the commute is highways.

Any suggestions would be greatly appreciated.

Best Regards,

Landmizzle

[Victor Laury]

I had mine lightened by Top End Performance

I chose them because thev'e done so many, I'm sure they know how much and where to remove the material. I can't really tell you if it's made a difference in my car's performance. It sure didn't hurt it's driveability.

[landmizzle]

Originally posted by Victor Laury

I had mine lightened by Top End Performance

I chose them because thev'e done so many, I'm sure they know how much and where to remove the material. I can't really tell you if it's made a difference in my car's performance. It sure didn't hurt it's driveability.

Thanks for the reply. The reason I was asking about "how light" to go is that I've heard that for street purposes, removing too much mass increases engine breaking and can cause too much of an RPM drop during shifting and thus create undesirable charectoristics.

Since I've never driven a Z with a lightened fly wheel, I'm pretty much coming at this blind. I appreciate you sharing your experience with me.

Best Regards,

Landmizzle '72 240Z

[gundee]

There is another option I was recently reading about. If you can find a Datsun 810 or Maxima L24 flywheel, it is 17.6 pounds compared to the 24 pound Z flywheel. I have not done it myself.

Just passing on info.

[2ManyZs]

Hehe, I've been thinking about the Maxima/810 flywheel myself... I believe it's supposed to have a casting number of Y-70 on the back.. just so you can double check it....

[frank13]

Hey landmizzle, don't you need a fly wheel first. Before you lighten it? What clucth were you thinking of running with your 5 spd. Some hi po flywheel can't be used with a stock clucth. TEP cut thiers down to I think it was 13 lbs? Stock flywheel for the Z's come in two different friction area sizes. The 2+2/ turbo being bigger face wise. But still having the same overall size, wheight as a regular Z flywheel. At TEP they also zero balance the flywheel. :devious:

[seerex]

who is tep , kinda researching for a flywheel was curious , thanks

[Bambikiller240]

Originally posted by seerex

who is tep , kinda researching for a flywheel was curious , thanks

Top End Performance in So Cal

[landmizzle]

Originally posted by frank13

Hey landmizzle, don't you need a fly wheel first. Before you lighten it? What clucth were you thinking of running with your 5 spd. :devious:

Hi Frank,

Well, if I go the easy route, I have the engine and 4 speed tranny from the 72 240Z I wrecked from last April that is still being stored with my mechanic. So.....I could use the flywheel from that car. My thought was to either use the flywheel as is or have some mass removed from it. As far as clutch, I was planning on using a dual friction CenterForce clutch.

My mechanic found an 82 280ZX 5 speed up in Sacramento (about 70 miles from where I live.) and is checking on it's condition now. This tranny should have the following gear ratio:

1st-3.062, 2nd-1.858, 3rd-1.308, 4th-1.0, 5th-.745

Compare this to the stock 4speed ratio:

1st-3.549, 2nd-2.197, 3rd-1.42, 4th-1.0

As you can see the 5 speed has a little taller gearing in 1st, 2nd, and 3rd. Which would slow acceleration, however I'm keeping the 3.54 differential from the automatic (vs. 3.364 from the manual equiped 240Z) so this should make the final gear ratio closer to the manual stock setup with the benefit of a nice 5th gear overdrive.

In my 71 240Z that I sold a few months back I had a 3.54 rear end and a stock 4 speed and really liked the combination with the exception that 1st was probably geared too low and at freeway speeds the engine was spinning too high (about 4000 RPM @ 70MPH.). 3rd gear was absolutely wonderful on curvey hilly roads and 4th pulled nicely at freeway speeds when needing to pass.

My thinking is that the 5 speed mated with the 3.54 rear should give me the best of both worlds; a more usable 1st gear, 2nd and 3rd close to the combo I had in the 71, and a nice 5th gear overdrive to drop the RPM's at freeway speeds and improve on gas mileage.

Well, that's the plan at least.....

Thanks for all the replies so far. I'll look into the 810/Maxima idea too.

Best Regards,

Landmizzle '72 240Z

[symon]

Dear Landmizzle,

I have done various gearbos & axle ratio changes in past, though not on a Z. The differences between the 4 & 5 speed box ratios in 1st, 2nd & 3rd will be hardly noticable but what you will appreciate is the extra high speed cruising. In my 260Z 5th gear runs 4.000 revs at 155 km/h ( approx 93 mph). This makes it easy to cover a lot of ground comfortably.

You wrote about lightening the flywheel. Well hear are my thoughts !

1. The reduced weight would show significantly in 1st gear, less so in 2nd, & in 5th the acceleration should be about the same as standard. This is all to do with the the geared down effect that the gearbox you. I´ll dig out the article I read about this when I come back after new year.

2. As you progesively lighten the flywheel you make the tick over rougher as the heavy original flywheel smooths out the relatively uneven firing sequence. Once the engine revs up you won´t notice any change.

3. A lightned flywheel makes it easier to stall the car when starting off. ( Maybe a few red faces here then ).

4. In my last 2 cars I lightened the flywheels considerable, for example my Triumph Stag´s 3,900 Rover / Buick aluminium V8´s flywheel went on a diet from 13,5 kg to 9,2. ( sorry don´t know how much that is in pounds. My MGB engine in my MG TD originaly had a 12,5 KG flywheel & now has a 3,5 kg aluminium unit that I knocked up in a weekend specially to use a 5 inch twin plate sintered clutch. Both of these cars have terrific performance in 1st , 2nd & 3rd. In 4th & 5th they are just bloody fast. The Stag pulls 0 - 160 km/h ( 0-100 mph) in 9.8 seconds, the MG does the same run at 9.2 secs.

5. My advise is reduce the weight as far as possible & enjoy the performance benefits that you can have without opening up the engine or cam changes, etc.

Ok that my view on all this.

Best of luck with the gearbox swop.

[frank13]

Hey Landmizzle, What did you end up Doing? Did you check out TEP's flywheels? How or what ended up happening to your ride? If you checked out TEP's site under the Datsun link to the lightened flywheel section they list the stock small flywheel and larger (friction area) of the 280ZX T/2+2 to the wieght they cut them down to. Just wondering how your ride came out. :devious:

[landmizzle]

Originally posted by frank13

Hey Landmizzle, What did you end up Doing? Did you check out TEP's flywheels? How or what ended up happening to your ride? Just wondering how your ride came out. :devious:

Hi Frank13,

A couple of weeks back I posted the results of my swap in the "General Chit Chat Forum". Below is a "cut 'n paste" of it. Sorry, I don't know how to link to it....

"You may recall my inquries to auto tranny swaps and lightened flywheels. Well, I just got my car back from the shop with the following modifications; 77 5 speed, Maxima flywheel, and a 2.5" exhaust with a Dynamax muffler. I left the rear differential from the automatic tranny in place (3.54 gearing). All I can say is WOW!. It's a completely new car!

I've already put a hundred and fifty miles on her today just driver her around and enjoying the new feel.

It's amazing how different she feels after losing the automatic tranny. Here's some observations;

Engine really revs freely and pulls strong with the lighter flywheel. No issues with stalling or revs dropping too quickly between shifts.

I really like the gearing the with the 77 5 speed and the 3.54 rear end. The car accelerates very briskly and the 5th gear drops the revs down nicely at freeway speeds. Prior to the swap, at 70 MPH, the engine was turning just over 4K. Now she's doing about 3.2K at the same speed.

I kept the stock exhaust manifold and with the new exhaust and muffler she sounds very throaty and burbles nicely. My prior 240Z had a Flowmaster muffler with a 2.25" exhaust. I like the sound of the Dynamax better. It still sounds nice and throaty but doesn't have the raspiness of the flowmaster. Oh, you can tell the exhaust has been tweeked, and it is diffently loader than stock but, it's not annoyingly loud and now has a wonderful charector to it's exhaust note.

Tomorrow, on the way to work, I'll take her on my favorite twisty moutainous road and I'll really be able to row through the gears and test out how the ratio stacks up. Should be great fun!

So far I'm extremely pleased with the results. The next week or so should be interesting as I really give her a run-through and see how living with her on a daily basis is. I'm really courious to see how the gas mileage will be affected by the changes. Prior to the swap I was getting about 21MPG. I expect the 5 th gear to help here as most of my commute is freeway driving. The lighter flywheel may take away some of the mileage I would have gotten had I stuck with a stock 240Z flywheel but, even so, I expect that I'll still see some improvment.

Anyhow, that's about it. I'm just so excited about the results I thought I'd share my experiences so far and maybe it'll help others who are contemplating the same thing. If you currently have an automatic tranny and would prefer to shift, you absolutely have to make the swap! You most diffently won't regret it. "

End of "cut 'n paste":

Since the above post, I've put about 2000 miles on the car and love everything that was done. The shifting was alittle stiff at first but is loosening up nicely now. Gas mileage only went up a little bit from 21 MPG to 23 MPG. I'd probably get better but I wind the engine out from most stops 'cause I like the acceleration and hearing the engine sing!<grin>.

It really is incredible the changes that this swap has produced. As I mentioned in my original post, it's just pure pleasure now driving a real sports car ( manual shifting......no offense to those that prefer automatics.)

Anyway, thanks for inquring about my baby.

Best Regards,

Landmizzle '72 240Z