180mm vs 200mm Flywheels

[gimmesomeshelter]

I'm having second thoughts about the 200mm (C/SC) flywheel I just purchased. The 200mm flywheel weighs a little under 16 lbs. A new 180mm flywheel weighs almost 20! While I'm sure the 200mm flywheel will work just fine, I'm concerned that a 20 lb. 180mm flywheel would provide a much smoother ride.

BTW, this is for a hot-rod 36hp project: 1600 cc, 356 crank/rods, dual Zeniths, Nickies, pre-a super cam.

Has anyone gone from a 180mm to a 200mm flywheel and regretted it?

Cheers,

Paul
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"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[Jacks]

Depends on what kind of car it’s going in
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Jack Staggs
Actual name

[Starbucket]

Lighter flywheel = quicker RPM's, Not good if you have a heavy car with high gear ratios. Builders used too lighten the 6 volt flywheels to help the motor get to the power band of the cam quicker. Make sure you balance the rotating assembly with all the changes you make. If you change back to a heaver flywheel everything will need to be rebalanced. Center Force Dual Friction clutch/pressure plate is the best "No Slip" option.

[gimmesomeshelter]

FYI, I'm putting it into a '57 VW Bug (1609 lbs).

Cheers,

Paul
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"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[cornemuse]

I once put a '65 C motor (w 200mm) in my '56 bug. I doubt you could see the diff 4 lb would make. VW speedo went to 70 mph, did that in 3rd gear. (I had large tires) Pegged the speedo in 4th so I dont know fast the car would go, , ,

Warning! SEVERE understeer at speed!! Be careful!! Also, hard on vw trannys.

Did this in the '70's, still have the bug (sunroof!), and the C motor.

-c-

(edit) click my "Gallery", bottom pics are the bug, (duh!) Still have the other two. (not the 1st one!!)

[63kombi]

Well, I would not use a 912 Flywheel in a beetle. You don't need the 200 mm clutch. And 6V starters work great with 12v - they last for years doing this as long as you don't abuse them. (i.e. cranking a dead engine for 2 minutes which you should never do with ANY starter).
But- if you want light and a flywheel that fits a normal/s 356 motor there are lightened flywheels a plenty. I have a spare one I don't want if anyone is interested. Otherwise Im giving it to a friend, those things are for race cars.
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1960 Beetle (third owner)
1963 Kombi (third owner)
1966 912
1968 Bug (first car- $100 03/04/80- still have it)
1972 Super Beetle
1973 Thing
1976 Type 2 (family heirloom)
1977 Westy
1981 911 SC Targa
1987 Westy
Gone but not forgotten - 63 Bug, 63 356, 64 Bug, 64 Sunroof Bug, 64 Kombi, 65 Bug, 66 Bug (2x), 66 Sunroof Bug, 67 Bug, 67 912 Targa, 69 Bug, 70 Bug, 70 Bus, 71 914, 74 412 Wagon, 74 412 Sedan.

[Formcar 179]

I did a recent rebuild of my since high school '56 Beetle with an Okrasa engine. I went for the 180mm flywheel.

The Porsche clutch, that is needed to hold the massive 52 HP at the wheels, demands more clutch pedal pressure. While it works, it puts more strain on the cable, and more strain on the pedal assembly. Such that I installed a special bronze bearing on the outboard side. Still not great. Depressing the clutch moves the brake pedal.

The better set up would be a 200 mm clutch with less spring.. My humble opinion.
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Porsche 356
'56 VW Beetle Okrasa
'70 Beetle Convertible
1944 VW factory Zollner Dynometer

[Jacks]

Are you using a Hauserman clutch? Those are a bummer. A similar Sachs 180 diaphragm clutch can be used and is terrific.
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Jack Staggs
Actual name

[ensys]

This discussion brings to mind an arcane point of physics.

While the total mass may be less with the 200mm, remember that a dense portion of that is 20mm further from the centroid. The longer lever means that meaty portion of the outer perimeter, takes that much more torque to start or stop.

Also keep in mind that the 200 carries more of its mass at the perimeter than the 180, which has more of its mass closer to the centroid.

To illustrate the point, suppose tow flywheels weigh the same, but one has an edge thickness of 1" while the other is 2". Which one do you think would spin up faster?

Back to real time, and while I can't back it up with math, I would peg the inertia of each to be fairly equal.

Just $.02 from the cheap seats.
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Keep 'em flying...

S.J.Szabo

[Danwvw]

I thought I would post here because I have some experience driving around in a 356A with a lighten flywheel. Also I like hearing about these Okrasa. 36 Horse based engines like "gimmesomeshelter"'s
My A had a "S" cammed 1600 356A engine with a really light 180mm flywheel and when I first got the car it had a slipping clutch. No Wonder! It was geared really tall in first gear much taller than a VW is and it was a bit difficult to start off on a hill in. It probably had a 8-11 lb 180mm flywheel on it. I went through several clutches over the 100,000 miles I put on the A. The best clutch for it was the 180mm diaphragm and it solved the problem somewhat but at some point the Porsche Transaxle went out on me and I put a VW transaxle in it. Really it was much easer to drive around town with the VW trans, it turned it into a bit of a dragster well not really. Buy Yeah, In a vw either flywheel would be fine I would think.
My current Beetle Engine 1679cc Type 1 VW with a full weight 6 Volt 200mm flywheel is very nice to drive.

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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[adam beefcake bruno]

I just finished installing this 356A motor in my '56 oval with one of those off the shelf AA 200mm conversion (lightened) flywheels and it seems to work great. Not so much on the 356 motor in my '61 bus (Even though I've been driving it since 2013). I really believe the bus would be torqueier if it had a full weight flywheel. I'm pretty sure the only 200mm Porsche motor to VW trans conversion flywheel on the market is lightened. If anyone knows any different, please let me know
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Don't take life too serious....you won't get out of it alive!

[Jacks]

15lbs or so works well with a light car. A meatloaf lunchbox requires a full weight flywheel. Aftermarket flywheels can be too light. One solution would be to use a 36hp flywheel. Easily fitted to 356/912 engines by machining 4 additional dowel pin holes in the correct location. Further machining can open the clutch size from 180mm to 200mm, allowing use of VW pressure plate, but depth problems might exist if you want to use a 356 sprung center disc. VW disc will fit fine if you want to use a solid disc. Depending on flywheel wear. I don’t recommend the sprung center VW 200mm disc, as the springs are smaller than 356 and prone to breaking when used in a bus (my experience). A worn out 200mm 356 disc is about the same thickness as a brand new VW 200mm and works well. More solutions exist.
Like your style. Delightful
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Jack Staggs
Actual name

[adam beefcake bruno]

[Starbucket]

[Jacks]

[adam beefcake bruno]