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Is a L28 Internal or External balanced? new flywheel?


dutchzcarguy

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Hi Guys,  I've got a question and i think i know the answer but not sure haha..

As i'm slowly ending the resto of my 280zx slickroof i'm considering a light flywheel on the L28. 

I think the flywheel and crank are balanced apart of each other as they can be bolted together on more than one way? (6) ..

I was thinking of putting one of my spare flywheels on a lathe and get rid of a few pounds haha..  Looked at a Fidanza flywheel but i think they are to light! (and also expensive!) 

And another question is do i need to re-balance the thinner flywheel? Has anyone here experience with this?

THanks! Mart.

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IMO, proper balancing of the rotating assembly includes the front pulley, crankshaft,flywheel, and clutch assembly.  If I went to all the expense and effort of a lightened flywheel, I would balance the entire assembly.  And as you say, if you can bolt it together in different locations, you should mark the pieces for any reassembly.

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2 minutes ago, 26th-Z said:

  And as you say, if you can bolt it together in different locations, you should mark the pieces for any reassembly.

I took a look (again)  in the serv.man. (L20A-L24-L26-L28 series engines) and there is nothing about marking any of the rotating parts before taking it apart..

As i can see that the crankshaft and the flywheel have both theire balancing drilled holes i asume that they are balanced apart..

It would be a good idea to balance it all together as a extra..  (But just don't think i'm gonna take it all apart AGAIN! 🙈)

I don't know how much a standard flywheel weighs, but i think it's more than twice the weight of a Fidanza ( seen 10,4 10,7 and 13 Lbs.) say almost 6 kg.  a original is over 10 kg easely..

On second thoughts.. i think i leave it alone haha..

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“If the crankshaft and flywheel were”

I just installed the fidanza flywheel to my “used” motor, I did not balance them (at all neither separately or as a unit) 

I think it would be BEST to balance them as a unit. I wonder what process a machine shop performs todo this, do they balance them separately then assemble them together and balance them again?

image.jpg

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When I build an engine for the race Z I have my machinist balance everything as a unit, damper pulley, crank, flywheel and clutch cover (the disk isn’t done as it will never stay matched to the rest). The damper is keyed, so it doesn’t need to be marked, but the crank, flywheel and clutch cover are marked with a center punch so they can always be reassembled in the position they were in at the time of balancing.

 

 

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11 minutes ago, 26th-Z said:

And if you really want to go whole hog, equal the weights of all the connecting rods and pistons.

I should have mentioned that my machinist always does that too, including the rod bolts and caps. In all the time I’ve been building engines the stock Nissan rods have never required adjustment to get them equal in weight. I forget the tolerance, but if memory serves me, a few tenths of a gram.

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8 hours ago, dutchzcarguy said:

And another question is do i need to re-balance the thinner flywheel?

Seems like you would, since the cross-sectional mass ratio (I made that term up) will be different on the side with the drilled balance holes compared to the side without.

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Thanks guys for the answers, i have not dicided yet but i take a fidanza or the original...i think the last, i like a engine that i can drive with 800rpm in high gear hahaha...  I often did this with my first 280zx (in the '90's..) and it astonished me every time again that i could drive that car till i was at home ON the driveway in 5th! without any stumble! (just don't floor it on low rpm's and all is well..)

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I'm pretty sure our stock flywheels are single mass. So when you replace it with a lightweight single mass I believe it is not supposed to make more noise.

However, I replaced my stock flywheel with the Fidanza one, had it all balanced, and now I have a bit more chatter in the transmission. Perhaps my transmission is a bit worn? Not sure,but it shifts good, doesn't wine at speed or have any noticable problems. Just a bit more noise. Now after 4,000+ miles I don't notice it.

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I can't rember the total weight of the rod and piston assembled but I used the ones that had the same stamped numbers on the cups and rod caps. I chose to grind off a gram or two off the outer longer length of the rods to get them equal. I had the the flywheel resurfaced and balanced by the machinest but bolted up the the clutch kit straight out of the box.

It gets close to 7,000rpm and is smooth, no vibration at all. Make sure and have your throwout bearing pressed on from your machinest. I used the old one to drive a new one on my first time and it whines in neutral unengaged. Works great but is annoying to me.

Heres something I found on a 2.4 build, good read.

 

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11 hours ago, siteunseen said:

have your throwout bearing pressed on from your machinest.

NISSAN calls them the releasebearing? and i'm surprised that you needed to press them on? I just fit it to the axle and ready..

And btw, i don't have a machinist..  (My engine needed just a clean up.. (after 120000km.))  I only took the head to a machinist to clean it in a special washing machine.

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