kunkle

Looking to put a lightweight flywheel in my 3000 lb. '71 w/ a 500+ hp small block. Looks like the flywhels run from 10 to 18 lbs.

Also have an '81 w/ 330 hp and an aluminum flywheel that someone else installed. Don't know how much that one weighs, but I like it a lot better than the stock iron in my '71. No downside whatever- no trouble getting it moving, etc.

I'm thinking to go as light as I can seeing how I've already got 500 hp in this little beast and can nearly dump the clutch at idle and it'll go.

So, how light would be too light causing driveability problems in this street car and is the stock setup 153 or 168 teeth? Thanks.

larrywalk

It depends a lot on your total first gear multiplication (RE x 1st gear). If you're ~10, a light flywheel works great; if on the other hand, it's only ~7 1/2 (like a 3.36 x 2.20), a heavier flywheel will work better.

gkull

As to your ideal flywheel weight. It's all gearing. I had a 4.11 with a 2.87 first that's over ~11 ratio in first gear and it took off with might light flywheel without a problem. I now went to 3.55 and I notice it 10.18.

kunkle

I thought the amount of torque had a lot to do with it too. I do actually have 3.36 rear and 2.20 1st gear (Muncie M21). When you say a heavier flywheel will work better with that gearing , what lbs. are you talking about? Thanks.

larrywalk

~30 lb, but it depends on what you're doing with the car. If daily driver usage, you'll need to slip the clutch much more due to stop & go situations, but if it's for road racing, that won't matter so you'll want the lighter flywheel.

Like gkull says, a light flywheel is great but you'll want to have ~10:1 total multiplication in first gear.

ED69ray

I have around 150 miles so far on my 440 hp sb :

15 lb L-88 nodular iron flywheel
2.87 1st gear TKO600
3:73 rear ratio
Hays Comp Dia 10.5 in clutch
27 in rear tire

...........and it rocks Clutch action is pretty firm and fast and it likes to be either on or off without spending much time in betweenbut its a freckin hot rod and thats ok. Its perfectly streetable but I would not want to spend lots of time in rush hr traffic.

But, If I was 3:36 final and 2.20 1st gear I'd want something in the 30 lb range

fugawi

i've got one of fidanza's aluminum flywheels. it's alot better than my stock steel flywheel. it revs faster,definite more power to the wheels. this is on a 383/500hp. motor with a muncie m-21.if you want easy cruising this is not the flywheel for you. if you want good performance, go for it..

kunkle

I want good performance- we're a little past easy cruising at this point anyway. What weight flywheel do you have?

kunkle

I thought the stock iron was about 30 lbs. to start with- now 2 of you said go with 30 lbs.? I know an aluminum flywheel is great on my '81 with far less hp than my '71- just no idea what weight it is. I don't see how a 30 pounder is gonna make any difference over what I have now? Thanks.

gkull

Stock flywheels and don't quote me were either are @ 30# or 40#. Stock small blocks were generally 153 tooth and you have to have a matching starter.

I've had small blocks with 168 tooth and aftermarket mini starters like proTorque. Aluminum flywheels kind of come anywhere from 11# - 18# I have an SFI billet steel 22 # 168 tooth 11 inch centerforce DFX clutch. block saver plate & blow proof bell housing with a GM longer pivot ball.

You have to look at the big picture. A vehicle with less rotating mass can excelerate faster. But you have to add up all the rotating parts. From the damper, crank shaft, flywheel, drive lines, disk brake rotors, wheels, & tires. Saving 10 pounds on the flywheel is not as good as having billet aluminum racing rear wheels that save 20 pounds.

One thing going for a lite weight flywheel is that it gives the motor the ability to change rpm faster between shifts.

airtime

I had a racing 355 small block with a m21 behind it with 3;55 rear gears. it had an aluminum flywheel. as stated above ran great, but drive ability suffered. had to have a few more rpm's to start under normal speeds and if i put it in 1st gear and tried to move (with clutch let out) slowly it would buck like a horse. of course that motor had a roller 305 solid roller cam but if you are pushin 500 hp then you have a big cam also.

ED69ray

What I was saying is that a 3;36 final w/2.20 1st gear is not the setup I'd want to run with anything lighter than the a stock 30lb wheel. Bottom line is you need better gearing.

We have been running aluminum flywheels on Ducati m/c's for years. Same principle and it totally transforms the machine.

The light wheel spools up much quicker, gives much snappier throttle response thru the midrange, and provides much better engine braking...........The downside is you cannot lug the engine at low rpm - especially when cold - and you must have proper gearing to prevent having to excessively slip the clutch everytime you start off from a dead stop.

TheSkunkWorks

If you've sufficient torque for given gearing the 15# works fine, and will make a significant difference in how quickly you'll be able to sync gears. This becomes particularly important when down-shifting under hard braking into a corner, should such spirited driving appeal to you.

IMCO, anyone who might complain that RPM's fall off too quickly between gears ought best to polish up their skills (and/or install a Hurst Comp + shifter), rather than think that's a down side. My $.02


TSW

SmokedTires

IMO aluminum is good for road racing where you want the engine to dump rpms quickly and be able to rev quickly in corners. Steel is good for drag racing and street driving because it helps the motor carry rpms between shifts. Think of the old tractors that relied on torque to get the job done, they all had big heavy steel flywheels to help keep the engine spinning when appling that torque. Thats why I say steel is good for street driving as well because your using less fuel to keep your engine spinning when highway cruising vs. the light weight aluminum that allows your engine to drop rpms quickly

airtime

when i was racing 2 stroke four wheelers, we used heavy steel flywheel for motor cross because it helped the motors carry the rpm thru the corners and get the motor moving coming out iof the corners and up steep jumps which were usually a short distance from a corner. flat track and sand dune racing used a small diamater and light weight flywheel for quick revving and rpm's. u could really tell the difference between the 2 flywheels

gkull

Well my drag bike and 750 road racing super bike did not even have flywheels or generators and they both had 7 multi disk dry clutch assemblies. But that is totally not functional for the street.

I never did hear the ci, so I would go for 22 pounds. But if its a big block you already have 10 pounds of extra crank shaft and a 15 pound aluminum would work

ED69ray

what kinda bike?

airtime

my point exactly, drag racing, dirt flat track racing or anything that is high rpm and needs to rev quick. for a heavy street car with a large cam i would stay with steel. alot of the imports use aluminuim flywheels but they have small cams and lighter cars and little torque. my old 68 camaro with 31 by 18 michey thompsons with a muncie and 4.56 gears would buck so bad idling in 1st gear it would bark the tires. lol

gkull

If you are asking about road racing I still have my 1 of 250 made 1983 Honda V-4 750's I raced for Coors light/dyno jet racing team out of Las Vegas Nevada in AMA pro racing. I'm an old guy, I was 25 back then making and spending allot of money on racing.

I raced lots of classes and bikes in both drag racing and road racing. Drag bike my fastest was a turbo 1335 cc susuki You are also taking 15 years ago, but it was 7.60's @ 170+ mph which is nothing compared to todays turbo bikes doing over 200 mph in the 1/4


I preferr cars with bars around you now

ED69ray

I was 18 and started riding street bikes in '83. I remember the V-4 Honda's well as that was the transition year from 1000 to 750 cc in the S-bike class. I recall both Honda and Suzuki had new 750cc models that yr. and I bought a 16v '83 GS750E brand new. It was pretty high tech back then - 16 in front wheel and alum swingarm w/ mono shock rear. I rode the wheels off that bike as it was my only form of transportation for many years. Here is a photo from around 1988 - in addition to the paint it was then at 802cc.



A riding buddy of mine had the '83 V-45 Interceptor - we used to swap bikes quite a bit. That V-4 had a nice flat tq curve and was much better on the street vs my peaky I-4 Suzuki.

I just sold that GS750 a few yrs ago - it had been apart for several yrs and I finally parted it out. I had lots of vintage Yoshimura and Vance and Hines stuff so it was worth a lot more that way.

I got away from the 4 cylinder stuff and hooked on Ducati's about 10 yrs ago. I have a '92 900SS now as well as a H-D Softail.

I know we are off topic but post a pic of your 750, I'd love to see it.

Thanks, Ed