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I'm looking for information on lightening a flywheel for a Manta with some performance mods but mostly street driven. I can tolerate some driveability loss. If anyone has any information/recommendations, I would appreciate it. If anyone is in the business and can lighten mine on an exchange basis, I would be interested, as well.

Thanks
Paul Crane
75 Manta
 

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Here are a couple of photos of my aluminum flywheel that I just had made for my 2.4L. A company in New York named Unorthodox Racing made it for me. It has a replaceable steel friction surface in case of a clutch failure. It comes with a new ring gear which is pinned and bolted to prevent it from spinning. I am sure they will make them almost any weight that you like, but mine is 8.4 pounds. I also had mine made to accept the S-10 clutch rather than the stock clutch.They are precission balanced and the quality is fantastic.
It would be much safer to go with a flywheel made from a billet like this one than to have a cast one lightened. The price for this flywheel was $550.00 including shipping.

Duane
 

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Similarly, here's a billet steel flywheel for use with a Chevy S-10 clutch. I had it custom made, it weighs 13 lbs

Bob
 

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Here's an extreme example of lightening a stock Opel flywheel. This is not recommended for street use! Weight was cut down from 23 lbs to 11 lbs. Flywheel still needs to be shotpeened, ring gear pressed back on, balanced, and resurfaced.

Bob
 

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PrOpeller
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Duane,

Would your aluminum flywheel with S-10 clutch combination still necessitate grinding inside the Getrag 5-speed bellhousing for clearance? Other than its cost and availability, would there be ANY good reason to use an Opel 2.4L 9" clutch assembly instead?
 

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Yes, it still requires minimal grinding of the bell housing for clearance. The actual size of the flywheel is the same as stock. I see absolutely no reason to use the 2.4 clutch over the S-10 set up unless you like spending too much money on hard to find parts. The S-10 clutch is readily available at any parts retailer and is very reasonably priced. The 2.4 clutch is extremely hard to come by, being available at only a couple of sources that I know of, and is insanely overpriced. I called the Sachs tech line to inquire about the 2.4 clutch and they said that it is not an imported item and it would have to be special ordered from their European division. They told me it would take several weeks to get and is very price prohibitive. Not exactly what you want to hear when your car is sitting waiting for a clutch.

I believe I was the guinea pig when I had mine made. I probably paid a little more because of the set up time for them to make it. I am sure they have the CNC program now so it would probably be cheaper to have more made. Depending on your intentions with the car, I would not compromise safety by having a cast flywheel lightened. There are many stories of amputated feet due to flywheels coming apart at speed.
 

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Yea, what HE said.........
 

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FYI

I contacted Jim at Unorthodox Racing. (I'm out of town on business and bored!)

They did not save the program for the lightened flywheel that they built for Duane and would need an old one for a model. They would build more next time if there was enough interest.
James
 

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Good timing I guess for you, I'm having a few made very soon by Unorthodox, so I'll be sending them a stock flywheel and the billet steel flywheel shown above, so they can integrate the lightened outer perimeter detail to make it even lighter...maybe 7 lbs? Probably a few weeks from now, they'll have my flywheels and they can re-do the programming. He said it would be about $535 for a flywheel, they couldn't promise any kind of price break until they made 10 or more at a time because then they'd run it on the CNC.

Bob
 

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Then I suspect we have to tell the guys at UR this, and not keep it to ourselves! They won't build 10 flywheels and keep them on the shelves for later on down the road when we have the money to buy them. My friend Gregg needs one immediately for his 2.2 litre (this is the reason I'm sending them a sample flywheel), and will eventually need one for his 2.5 turbo and his 2.7 turbo, and I will need one for my Dad's 2.7 as well. But, since I just spent a bunch of money on roller cams and on racing scales, for me this ain't happening at the moment! Gregg is getting married in two weeks, so he's decided to just get one for the moment. So as it stands, we need to get 8 other people interested in a 7-8 lb aluminum flywheel for use in an Opel CIH engine with a 9.125" Chevy S-10 clutch. Any other takers?

Bob
 

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Bob,

race scales...and only 2 hours away...hrmmmm:)

Why did you decide to go with UR? I know you had had some made a few years back by 10,000rpm. Any reason for not going back? Just curious...

-Travis
 

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Yea, and they're kick-ass scales, not the cheapies. They had a special deal on them because they're dropping this model from the lineup, they're $2000 scales plus a $340 scale cart for $1300, so I couldn't pass them up. They're also LED readouts with a HUGE screen instead of the typical LCD's that you need to be two feet away from. You can see the numbers from 30 feet away, and you get all the typical percentages, FR/RR, LH/RH, diagonal splits, etc. If you're in the area we can scale your car, no problem there. I scaled three cars with them the first night I got them, it's pretty easy stuff to do, the hard part is getting the correct cross-weights for the different tracks. And setting my friend's front-drive IT car, whew! How about 64% front weight! I long for the days of my 50.2/49.8 Ascona after seeing that one.....

Reason for not using 10,000 RPM? They make flywheels for their clutches primarily (small dia racing clutches), and a minimum buy-in is $2500. I spent $4200 on my buy-in, but that went out the door when I closed the business down. I could have them make a custom one-off, but then we're talking a lot more money.

Bob
 

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I'm in the market for a flywheel, But (yeah but) 1. I don't really have the cash right now, and 2. How streetable would a 7lb. flywheel be? I was thinking about a 10-14lb flywheel would work good for a somewhat daily driver. I'm not sure if I can scrape up the cash, but I'd be in for one if I could.
 

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Greg,

I'm in the same boat as you right now. I'm trying to line up the parts I want to use for my rebuild, while also trying to set aside the dollars needed when I jump in.

I wasn't interested in getting a new lightened flywheel at first until I realized that getting mine machined for the S10 clutch would be almost $200. I now think that it would be better to send $500 for a new lighter one then throw more money at the old old. Besides, I not real impressed with the automotive machine shops I have seen done here so far. I'm still looking.

I'm also thinking more like 14# for street use.
James
 

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Well, I don't think they could even GET 14 lbs out of an aluminum flywheel! That's a big chunk of aluminum! Duane's was about 8.5 lbs, and as mentioned, I was going to contract UR to make mine lighter to match the perimeter 'scalloping' that I had done to my custom steel flywheel, which should make it around 7 lbs. One thing to consider is that a 9.125" Chevy clutch weighs about 3 lbs more than the Opel's 8" clutch, and simply because of the larger diameter it has more inertia. I haven't done the math (I'm not much for physics), but I believe the larger Chevy clutch with the light flywheel should behave similarly to the Opel clutch with a 14-15 lb flywheel. I had a Chevy clutch in a stock Opel 1.9 and the flywheel weighed 14.5 lbs, and it was very easy to modulate and drive, as good as stock or better. The Chevy clutch diaphragm is larger, and because of this the clutch arm adjustment is altered (to 4.75" instead of 4.25"), and the pedal effort is lighter and over a slightly longer travel, so engagement is easier on the foot, almost like a hydraulic clutch.

Bob
Hating the heat and humidity in New England right now, it feels kinda like N'awleans........
 

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Bob,

Would it be okay if we took this to the ClassicOpels list? Should be able to find eight (if not more) to ensure cost-effective CNC tooling of the flywheel.

Walter
 

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I have no problem with going 'public' about the flywheels, the issue is not trying to find 10 people who want them, the issue (as usual) is finding 10 people who want them AT THE SAME TIME, and have the money to do so!
As I said, I will eventually need one myself, but not at the moment. My friend only needs one at the moment in order to get one particular car together. We don't want to wait too long however, it needs to be ordered in the next week or so. The differential I'm nearing completion on, then I have to install it in the car, replace the metal brake lines, have the brake booster rebuilt, install my custom big brake setup in front, and get the roller cam into the engine. Bolt up the flywheel and clutch, throw in the ZF tranny, and it should be just about done.

Bob
'Man of a billion projects...and the list never ends'
 
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