alluminum flywheel?

[902066]

If you have a lightweight flywheel in your ZR-1, do you love it, or hate it, and the reasons why? I am seriously thinking of adding one but am on the fence. I do have 4:10s, stainless works headers and corsa exhaust. I would think these 3 should help if I go with the flywheel. Thanks Jim

[BigJohn]

You would never feel the difference!
Lighter rotation mass; engine should Rev quicker

[conesare2seconds]

No thanks.

[Demps]

I?d ask a few questions back to make sure that I answered your question correctly:

How do you use the car? Street, drag, track?
Will you do the work yourself or outsource it?
Do you mind holding the clutch at stoplights?
Do you mind weird gearbox rattle?
Would you like quicker revs?

Not trying to be snarky. I like them but they come with sacrifices.

Not knowing the answers above here?s my stab:

If you can do it yourself yes.
If not, have the top end ported & new chip/tune.

Ted

[902066]

I?d ask a few questions back to make sure that I answered your question correctly:

How do you use the car? Street, drag, track?
Will you do the work yourself or outsource it?
Do you mind holding the clutch at stoplights?
Do you mind weird gearbox rattle?
Would you like quicker revs?

Not trying to be snarky. I like them but they come with sacrifices.

Not knowing the answers above here?s my stab:

If you can do it yourself yes.
If not, have the top end ported & new chip/tune.

Ted
I'll try to answer your questions. I am basically a waxer and a cruiser. the work will be outsourced but a lot of other things are being done at the same time. I always hold the clutch at stoplights. I could live with some gearbox rattle, just not real loud and only somewhat annoying. Whats not to like about quicker revs? Its probably not real practical for me, but unless someone absolutely hates it and can tell me why, I'll probably do it. Thanks for your reply.

[Zman]

Here are my thoughts about your situation. I have a 368 with 4:10S and an aluminum flywheel. The car is bat chit crazy! But, I feel 4:10S or an aluminum flywheel is a better combo. I say this because I have a 385 with 4:10S with a stock flywheel and at times this is too much. I agree with keeping the stock flywheel with 4:10S. The reason I say this is because an aluminum flywheel is a crap shoot as to how rattlely it will sound. It will allow your RPMs with 4:10s to be gone too quickly. I wouldn?t do it. Both do about the same thing as for drivability but too much of a good thing is not always best. Like Demps said....port and chip.

[902066]

Here are my thoughts about your situation. I have a 368 with 4:10S and an aluminum flywheel. The car is bat chit crazy! But, I feel 4:10S or an aluminum flywheel is a better combo. I say this because I have a 385 with 4:10S with a stock flywheel and at times this is too much. I agree with keeping the stock flywheel with 4:10S. The reason I say this is because an aluminum flywheel is a crap shoot as to how rattlely it will sound. It will allow your RPMs with 4:10s to be gone too quickly. I wouldn?t do it. Both do about the same thing as for drivability but too much of a good thing is not always best. Like Demps said....port and chip.


Makes a lot of sense. I think I'll take advice from both of you and keep the stock flywheel. Jim

[Zman]

I think you have the perfect combo if you were to port and chip your car.
Ported, Headers, 4:10s, chip and tune. Perfect. Much more you will lose your street driving enjoyment in my opinion.

[Paul Workman]

I've got the 13# Fidanza Al in my 500+ HP car with stock 345s and Ami has (I believe) one in her 500+HP Z w/ 410s.

My cams are stock and the idle is set @~900 and I have NO rattle to speak of.

Ami's car has an AL flywheel & Pete's cams (and mild porting) and it rattles some.

Both cars are perfectly streetable to the point of not ever giving it a second thought in normal driving.

The PHYSICS favors the lighter FW when RPM is changing: the faster the change in RPM, the less energy is absorbed and that power goes to the rear wheels. That equated to very noticeable increase in the "snap" felt in the seat of the pants, especially in the lowest two gears! In fact, the rear end often breaks loose in first gear with only the accelerator on my car (with the stock 345 diff @ that!)

Some prefer the stock FW, especially for drag racing. A lot of energy can be stored in the FW at launch which can be beneficial as the clutch is released. However, the dyno graphs tell the story when it comes to putting it on the ground: it costs as much as 15-20 HP in 4th gear (on a 500+ HP 350 cid LT5), AND A WHALE OF A LOT MORE in 1st, 2nd, & 3rd! (as the CHANGE in rpm is higher in the lower gears - especially noticeable in FIRST!)

It only took me a single outing to become accustomed to the different feel (and there is some). But, after that I never give it a second thought in the ?10 years and 30k miles of spirited driving!

So, is it worth all the hoopalah? Some say yes, others say no. It depends a lot on your preferred driving style - what you like. My favorite is mountain twisties or the track where much of it is in 2nd and 3rd gear (especially in the mountains). I really like the snap the Al FW provides when coming out of a corner. I can only imagine how much more it feels like having 410s IF the gear changing doesn't get too annoying; someday I'll get to try the wife's car in the twisties with her 410s & comparable HP.

Bottom line? For normal or stop and go driving, it will only take a few minutes and you'll be accustomed to the difference. After that, and I doubt you'd ever give it another thought. But, you'll notice the extra "snap" in the twisties...for a while...and then you become accustomed to it and never think about it UNTIL you jump into a car with the stock FW. SLUGGISH, at first.

I like my aluminum FW and would not go back to stock. I like the quick RPM response "seat of the pants" feel, primarily whenever the lower gears are involved along with WOT. For normal driving - especially if (Pete)s cams are involved, maybe, MAYBE the stock FW is the choice.

But, hey! You needn't go to one extreme or the other. There ARE choices in between the 13# Fidanza and the 43# stock dual mass - such as the 18-25# single mass FWs some prefer. Just sayin...

[dredgeguy]

If you have a lightweight flywheel in your ZR-1, do you love it, or hate it, and the reasons why? I am seriously thinking of adding one but am on the fence. I do have 4:10s, stainless works headers and corsa exhaust. I would think these 3 should help if I go with the flywheel. Thanks Jim

Jim,
Don't know where you are located but I have stock dual mass flywheel, 4:10's, top end porting and chip/tune by Haibeck, Stainless works headers with high flow cats and Corsa. If you are in the MD area you can take my 92 out for a spin and see what you think. Like others have said, some lightweight flywheels rattle like rocks in a can and some do not. I did not want to take the chance of rocks in a can and mine is plenty fast for me...scares me at times!

[Hib Halverson]

It's not the aluminum flywheels that rattle.

It's the transmission. The correct nomenclature is "gear rattle". It happens at idle and at very low engine speeds under light load. It occurs because, at idle and low engine speeds and only four firing impulses per revolution, engine speed actually fluctuates enough at a low frequency that the main drive gear and the counter gear start "rattling" because of the clearance between the teeth.

In the manual transmission nomenclature, "center distance" is the distance between the centerline of the drive gears and the centerline of the countershaft. The greater the center distance, the more pronounced the gear rattle will be. During early development of the S6-40, it was quickly obvious that gear-rattle was a problem.

The dual-mass flywheel designed for the first LT5?one of the first applications of that technology in a light vehicle?was a partial solution to gear rattle. The flywheel had a spring damped secondary mass the purpose of which was to "smooth out" the torque fluctuations caused by firing impulses at idle RPM.

Install an aluminum flywheel, which is a standard or "single mass" wheel, and you eliminate the gear rattle mitigating the function of the dual mass wheel. With an early-style, 610-Nm transmission, the increase in rattle is very noticeable. With a late-style, 540-Nm transmission, the increase is noticeable but not so bad.

As I was not a drag racer and liked the quicker engine acceleration which comes with an aluminum flywheel, I installed a McLeod aluminum wheel in Barney, my dear-departed '95 SN 140. There was an increase in rattle, but I cut that about in half by installing higher output ignition coils, then opening up the plug gaps by .010 or so and going to Red Line Lightweight Shockproof Gear Oil which used a calcium-based EP additive package that has a cushioning effect between gear teeth.

Those solutions would still be valid, today.

[Karl]

Thanks for the tips Hib. I have a spec aluminum flywheel and it weights ~18 lbs. Gear rattle is minimal compared to the fidanza. I also use the redline oil.

What high output ignition coils were you using?

[EvanZR1]

I have Pete's 391 and stage 2 cams with stock clutch & flywheel and the trans rattles a good amount, would hate to see what it's like with an aluminum flywheel. Doesn't really bug me much as the car is already loud and obnoxious. If I was running a car with stock cams, I don't know if I could bring myself to run an aluminum flywheel because the rattle would stand out more.

[efnfast]

I have a light weight, single mass flywheel. Not a big fan of the rattle, but just couldn't leave that additional hp laying around. ( I know, it's really not hp.)

[Hib Halverson]

Thanks for the tips Hib. I have a spec aluminum flywheel and it weights ~18 lbs. Gear rattle is minimal compared to the fidanza. I also use the redline oil.

What high output ignition coils were you using?

At different times I had either Performance Distributors or MSD coils on my engine. I ran Denso IT22s with the gaps opened up about .010 more than the stock gap. The idea there was a bigger gap exposed more of the air/fuel charge to the spark. In some cases that would light a lean air/fuel charge which otherwise would not ignite making for a misfire.

The gear rattle is always worse if there is a misfire at idle. My strategies were to 1) reduce misfire at idle with hot coils and 2) bigger plug gap.

The "cushioning" effect of the calcium-based EP additive package in all Red Line Shockproof Gear Lubricants, mitigated the gear rattle problem.

I was never able to get rid of all the gear rattle increase from the use of an aluminum wheel, but I did reduce it such that it was less annoying.

[Karl]

At different times I had either Performance Distributors


Do you have a part number or source for the Performance Distributors ignition coil?

[BigJohn]

Now you have me Confused again!

[Karl]

I believe this is the part

https://www.summitracing.com/parts/dui-31727

https://www.summitracing.com/parts/dui-31733

"Screamin' Demon Coils"

*edit will these fit under the plenum without any issues?

[Paul Workman]

Here is my LT5 with the 13# Fidanza FW. The idle was bumped to 900 AND, per Marc Haibeck and Hib's suggestion, I switched to the Redline Heavy Shockproof gear oil. Oh, also, the temp was ~ 25?F (in the video), but in fact the rattle (or LACK thereof) is also still true of summer temperatures - FWIW. The coils are stock GM AC/Delco and the plugs are good ol' copper core AC Delco 41-602s gapped @ .042" per Pete Polatsidis'

In contrast, Ami's Z has Pete's cams and AL flywheel, and it idles with a righteous sound thru the B&B catback, but it rattles in neutral like a box of rocks(!). (I doubt a ▲ of gear oil (to Redline or whatever) would make much difference tho...)

https://www.youtube.com/watch?v=y1YFa8ruh8A

[Flyman 27]

When I purchased my ZR-1 it had a Fidanza aluminum flywheel in it. I absolutely hated it. It rattled loudly and I really got tired of explaining to everyone that the engine was not going to blow, it was just trans gears rattling. I am running a Haibeck 500 pkg.
Mark swapped a dual mass flywheel & clutch asm and I could not be happier with it. It is quieter, shifts smoother and no more rattles!
That's my 2 cents.

[Ccmano]

As has been mentioned a light weight aluminum flywheel may or may not cause transmission rattle, but likely will. Mine has moderate to loud rattle. One thing that can be done to mitigate the rattle is a countershaft shim kit that is very easy to install with the trans out of the car. Carolina Clutch provides such a Kit. It will be my next winter project.
H
:cheers:

https://www.carolinaclutch.com/product/corvette-c4-shim-kit

[tf95ZR1]

Thanks, Hans! I never heard of this shim kit,
or that this might help with the rattle. Anybody
have any experience with the kit? Does it help?

Ted

[Ccmano]

Thanks, Hans! I never heard of this shim kit,
or that this might help with the rattle. Anybody
have any experience with the kit? Does it help?

Ted

Ted,
This is the exact same thing Bill B does when he rebuilds a trans and sets it up for an aluminum flywheel to minimize rattle.
H
:cheers:

[-=Jeff=-]

This may not be apples to apples comparison.. but I had an 89 mini ram car before the ZR-1. It had a centerforce steel single mass flywheel, weighed close to the dual mass, car was fun to drive. I installed a fidanza aluminum one. I hated driving the car after that. Was more of a chore than fun to drive on the street. My 1990 ZR-1 has exhaust, headers and 4.10s with stock flywheel. I love driving it. Since you are having the work done I agree with Ted and Zman, port and chip it.

[Hib Halverson]

Do you have a part number or source for the Performance Distributors ignition coil?

I'm sorry but I don't. That was one of the modifications I did to the engine at the same time Van Dorn was working on it. All that happened in 1997/1998 and I do not remember the PN nor do I have any of the invoices from back then.

Sorry.

If I had to do that again, I'd just use the MSDs.

[Karl]

I'm sorry but I don't. That was one of the modifications I did to the engine at the same time Van Dorn was working on it. All that happened in 1997/1998 and I do not remember the PN nor do I have any of the invoices from back then.

Sorry.

If I had to do that again, I'd just use the MSDs.

No worries. I purchased the screamin demon coils and a set of their live wires in yellow from Jeg's.

Should be here soon!

The coil's on my car are the one's that came with it and I want a hotter ignition system and a wider gap on my plugs.

[tf95ZR1]

As has been mentioned a light weight aluminum flywheel may or may not cause transmission rattle, but likely will. Mine has moderate to loud rattle. One thing that can be done to mitigate the rattle is a countershaft shim kit that is very easy to install with the trans out of the car. Carolina Clutch provides such a Kit. It will be my next winter project.
H
:cheers:

https://www.carolinaclutch.com/product/corvette-c4-shim-kit

PS: This shim kit is actually a Bill Boudreau product.
He may sell them directly.

http://www.zfdoc.com/

Just Sayin'

T