Machining the flywheel on a '37 flathead.

[cretin]

I've done some searching, but haven't found what I'm looking for.
I have a '37 Flathead that I'm currently rebuilding. I'm keeping the stock flywheel, just trying to lighten it up a bit. I have already machined the lip on it down to the clutch surface, and that has removed 8 lbs. so far. I would like to get maybe another 6 lbs. out of it.

I haven't really planned out where I can remove more material yet, so I thought I'd ask if anyone here has done it or had it done and has photos of where more material was removed.
I was thinking I could taper the edge, or machine some more off the edge, leaving a large radius if that makes sense.

I asked this on the HAMB also, but i know there is a lot of flathead knowledge here, so hopefully there is someone with experience on this.

 

[Vanspeed]

I have no idea what else you need to do but I like how you got 8lbs out of it already. I have a 37 going in my 35 and it is a heavy sucker! Going to keep an eye on this thread.

 

[russcc]

I have seen some where they machined the backside of the flywheel when there was extra meat. I have a stock early steel flywheel, that was turned on the backside, and weighs 26#s, twice the weight of an aluminum flywheel, but probably just about right for the '40 with 3&5/16x4" 59L

 

[flatheadmurre]

Cut it down outside the pressureplate bolt circle, leave enough to have the starter gear stay in place.
You win most in cutting the outer meat off a flywheel further in it doesn´t give you as much difference in moving mass.
What you end up with in weight depends on car weight, engine and driving style
18-23Lbs...
I took a pic of the web to show what i mean about cutting down outside boltcircle.
Don´t go crazy on cutting down the backside where the pressureplate bolts to it.

 

[34PKUP]

I've done some searching, but haven't found what I'm looking for.
I have a '37 Flathead that I'm currently rebuilding. I'm keeping the stock flywheel, just trying to lighten it up a bit. I have already machined the lip on it down to the clutch surface, and that has removed 8 lbs. so far. I would like to get maybe another 6 lbs. out of it.

I haven't really planned out where I can remove more material yet, so I thought I'd ask if anyone here has done it or had it done and has photos of where more material was removed.
I was thinking I could taper the edge, or machine some more off the edge, leaving a large radius if that makes sense.

I asked this on the HAMB also, but i know there is a lot of flathead knowledge here, so hopefully there is someone with experience on this.

After you cut down the flywheel to your satisfaction, what do you expect to achieve?

 

[skidmarks]

Better throttle response. I have cut a bunch of them. Another slang term is chopping a flywheel . Int a light weight car you don't need the weight for pulling tree stumps

 

[JSeery]

Yep, increased acceleration. From Rumbleseat:

"LIGHT FLYWHEELS: The “lip” type flywheel used a 9" clutch and weighs 38.7
lbs. They came in all of the early V8's. They are my preferred flywheel because
they use the lightest clutch (bet you’ve already figured out I’m some kind of nut
about light rotating mass). Beginning in ‘35, the pickups and sedan deliveries
all used a flywheel without a lip, but still used a 9" clutch. These weigh 34
lbs. They were much sought after for stock cars where rules stipulated flywheels
had to be stock. Most other early flywheels, other than the lip type 9", weigh
36 lbs. The 8BA and 8CM flywheels weigh 34 lbs.

Lightening a lip-type flywheel: Machining the flywheel’s lip off, chamfering
outward from the edge of the pressure plate to the starter ring gear, dishing out
the rear of the flywheel to reduce the flywheel thickness, will reduce the 38 lb.
weight of a lip type flywheel to about 20 lbs. Combined with the lighter 9"
clutch, they are my preferred combination for a street flathead.

On street machines, flywheel weight is best left at 20 lbs. (A light high boy
roadster with a built-up flathead and low gearing would certainly be an
exception.) If the flywheel is too light, it’s difficult to launch a heavy car
at stop lights without revving the engine considerably. Aluminum flywheels with
no steel or brass facing wear quickly and don’t take kindly to clutches being
slipped. I don’t use an all-aluminum flywheel (no steel or brass facing) on the
street. A steel or brass faced one is less than the 20 lb weight rule I use.

In the early days we all heard and believed the following: “During acceleration
every pound of flywheel weight is the same as adding 100 pounds of weight to the
car.” Seems to me this would apply to all reciprocating masses like the
crankshaft, clutch and flywheel."

 

[GOSFAST]

I wouldn't recommend lightening the flywheel unless you're planning on lengthening the stroke.

A slightly heavier wheel would be beneficial with a short stroke unit, this is just generally speaking, sort of a "rule-of-thumb" so to speak.

Thanks, Gary in N.Y.

P.S. Having said that, we have done a number of these on the 8BA platform. You can get a fair amount of weight from a conventional wheel. See the photos below here!

 

[JSeery]

I wouldn't recommend lightening the flywheel unless you're planning on lengthening the stroke.

A slightly heavier wheel would be beneficial with a short stroke unit, this is just generally speaking, sort of a "rule-of-thumb" so to speak.

Thanks, Gary in N.Y.

P.S. Having said that, we have done a number of these on the 8BA platform. You can get a fair amount of weight from a conventional wheel. See the photos below here!

Gary doesn't it depend on the final objective? A truck hauling heavy loads? A stripped down coup looking for better acceleration? A full bodied stock street driver? And then what about the rear end gears, the transmission type, etc?

For me, I want the lightest flywheel and pressure plates assembly I can get by with coupled with low rearend gears. But then I'm not into stock full bodied parade cars!

 

[cretin]

Lightening a lip-type flywheel: Machining the flywheel’s lip off, chamfering
outward from the edge of the pressure plate to the starter ring gear, dishing out
the rear of the flywheel to reduce the flywheel thickness, will reduce the 38 lb.
weight of a lip type flywheel to about 20 lbs. Combined with the lighter 9"
clutch, they are my preferred combination for a street flathead.


[/I]

Ok, so it sounds like the way for me to proceed is tapering whats left of the lip area from the pressure plate mounting out towards the ring gear.
I figured thats what I should do, since there is still a lot of mass there.

Thanks for the replies guys.

 

[Kahuna]

My flywheel was cut from 35# to 23#.
Both sides were cut.
It works fine.
Another 12 lbs removed from the car's overall weight

 

[TomT/Williamsburg]

My avatar has a 9" setup and I cut the heavy lip off and reduced it on the backside as well to about 23# total weight. Works great for the light weight of my car ....

 

[GOSFAST]

Gary doesn't it depend on the final objective? A truck hauling heavy loads? A stripped down coup looking for better acceleration? A full bodied stock street driver? And then what about the rear end gears, the transmission type, etc?

For me, I want the lightest flywheel and pressure plates assembly I can get by with coupled with low rearend gears. But then I'm not into stock full bodied parade cars!

Hi "J", absolutely correct. It's all about the overall combination!

Another example of when to use a lightened wheel would be for roundy-round racing where you'd want the RPM's to come down as quick as possible going into the turns. It's all relative!

Thanks, Gary in N.Y.

P.S. Care needs to be taken when machining these wheels, you can reach a point where there will be a tendency to start "cracking", as in heat cracks.

 

[cretin]

I made my next cuts today and got another 4 lbs off the flywheel for a total of 12 lbs lost. That makes my flywheel 27 lbs, and I'm going to go ahead and leave it there.

Thanks for the advice everyone.

Vanspeed, if you have any questions about what i did, let me know.

 

[Walt Dupont--Me.]

I always have my cut down wheels balanced, while doing that, bolt on the pressure plate, I've had a lot of pressure plates out of balance, I had one plate 100 gram out of balance. Walt

 

[PeterC]

Just as a note of interest - I run a 14lb aluminum steel faced aluminum flywheel in my 35 coupe with 4:11 - admittedlyI have high horse/ high torque flathead - very strong off the line performance and a real pleasure to drive.