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Discussion Starter · #1 ·
Evening,

Does anyone have a drawing to show how much can safely be machined off a 1600 flywheel?

Thanks,

Kevin
 

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This is a matter of experience rather than exact measurement. There are areas that just shouldn't be cut, and others where considerable material can be removed. Most of the machinists that do this work aim for a particular weight reduction from the way to heavy 22 pounds. It is not hard to get to 15 pounds. Check with Richard Jemison, Alfar7 on the BB. He has one or two giant lathe's and likes to make these lighter. Unless you have a big lathe, and some junk flywheels to practice with, this job is best left to one really familiar with lightening them. Clutch and flywheel blow-ups are always VERY destructive.
I gave up lightening the iron and nodular iron flywheels in favor of aluminum flywheels some years ago. One properly lightened just slightly, failed due to an air inclusion right outside the bolt circle. The clutch/flywheel assembly danced around in the bellhousing like a spinning top, completely ruining the bellhousing transmission and case. Fortunately, it remained contained, the car and driver were spared.
On the other hand, I ran a 14 pound lightened iron flywheel, cut by Ron Neal at AUSCA, for many years behind my GTA engine. I never had any problems.
Have your 1600 wheel done by someone with experience, or go with aluminum.
 

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Richard Jemison
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Lightened flywheels

I have a couple of lightened 1600 flywheels. Both about 14-15 lbs.
Balanced
 

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Discussion Starter · #4 ·
gordon,

i wouldn't attempt this myself. thanks for all the info, i want to give my machine shop some guidance!
 

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Ah! Richard's here! Back from vacation with flywheels! Give hi a call.
RJ, I like the new picture!
 

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I don't use lightened nodular iron any more, preferring aluminum as mentioned above.
 

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Richard Jemison
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Lightening flywheels

Most of the horrors of exploded flywheels are expanded BB urban legend.
I have built them since the `60s and have never had any fail. Nor in this time racing have I personally observed a clutch/flywheel failing.

Incorrectly lightened ones may well fail. However the extremely heavy cast ones are truly less likely to fail after lightening, as stresses on the castings are far less due to reduction in centrifugal weight and load.
Weight & thickness are not your friends.

If you look at the severly lightened one as done by Ausca that GR has(I had one as well with 45 years of race use on it) the tonnage is removed and it is still together.

Done correctly they are perfectly usable at far higher rpm than you run race motors.
 

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The big thing to note from RJ's comment is "INCORRECTLY LIGHTENED ONES MAY WELL FAIL." I have seen one incorrectly lightened fail this year. It broke (fractured) around the bolts on the end of the crank. This was at a high rpm shift to 5th. It all remained assembled for about 15 seconds as the engine continued to rev, not connected to anything. I'm not sure if the clutch / bell housing, or engine exploded first. It all let go with enough force to tear the engine and transmission from the mounts, as one rod went through the block at an engine mount boss. #1 rod came out the other side. The crank broke, there was no bell housing left, and the front of the transmission had the input shaft neatly removed.
The flywheel was intact, with only the hub missing (still on the crank). It had been cut in back for lightening, and at the hub was about 5 mm thick. Apparently, not thick enough.
Flywheels should be lightened by those that have done so successfully, more than once!
Driver was uninjured.
 

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OR.. Send your cast one to Richard to lighten with his giant lathe.
 

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I have personally had a CI flywheel explode at 6500 RPM on a street 1600 Giulia. Really lucky that I did not get hurt. It took out all kinds of things. Including the push rod on the brake master cylinder. NO brakes! Bellhousing, clutch, transmission requiring lots of work. I only use aluminum flywheels now. Or get yourself a 1300 flywheel. Much lighter than a 1600.
A 1600 Spider that I had bought with an " Autodelta 1600 Veloce race engine" apparently had an original lightened flywheel. After examining the parts left of the flywheel, one could see square cuts where it came apart. No smooth radius cuts.
Only good thing about the drag race was that I was beating the Sunbeam 289 Tiger! In about 1971 is when this happened.
 

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Hotlegs reasoning is why I personally only use aluminum now. I've seen alfa clutches come apart in both, and aluminum contains the shrapnel better, even if it does come apart with the clutch. As I stated earlier, I suggest the the use of aluminum to customers. If you want to use lightened iron, have it done by someone who HAS lightened iron Alfa wheels before successfully.
 

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With the readily available aftermarket flywheels available today I think you would not want to run a lightened stock unit no matter who or how they did it. It is to simple to say they only blow up if not lightened correctly.

Scattershields are a must on Alfa race cars. 35 years ago I saw a lightened flywheel done by Shankle Engineering and recently crack checked come apart on a 101 Spider. One of the broken off post came through the bell housing then went completely through the front side of the pressed frame section, then hit the other side of the formed frame section not just denting it but splitting it and almost getting through before laying down to rattle around inside. You don't want you foot anywhere near that.
 

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Based on Gordon's recommendation, I had my aluminum flywheel made by Peter Tomashevski in LA. Excellent quality. The flywheel is almost too pretty to install: $550 with ring gear and shipping.

If you're going to the expense of building a performance Alfa motor, for reasons already stated, using anything other than an aluminum or purpose built steel flywheel seems to me to be a false economy.


Peter Tomashevski <[email protected]>
 

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Richard Jemison
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Flywheel

Another question, how come the lightened flywheel up top doesn't have the centering pins for the clutch plate?
Those fall under the "improperly lightened" category.
 

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I have personally had a CI flywheel explode at 6500 RPM on a street 1600 Giulia. Really lucky that I did not get hurt. It took out all kinds of things. Including the push rod on the brake master cylinder. NO brakes! Bellhousing, clutch, transmission requiring lots of work. I only use aluminum flywheels now. Or get yourself a 1300 flywheel. Much lighter than a 1600.
A 1600 Spider that I had bought with an " Autodelta 1600 Veloce race engine" apparently had an original lightened flywheel. After examining the parts left of the flywheel, one could see square cuts where it came apart. No smooth radius cuts.
Only good thing about the drag race was that I was beating the Sunbeam 289 Tiger! In about 1971 is when this happened.
Judge, the defense rests.

b :cool:
 

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The 1600 flywheels (and many 1750's) did not use the pins, counting on the bolts to hold THICK PP plates where they are supposed to be. Thinner body plates result in FLEX and pins are useful. When you get to the tractor type 2L's that RJ prefers, there is so much low end torque on hand that you can rip flimsy diaphragm clutch PP's apart, thus the necessity for GOOD racing 2L PP's WITH pins. With good 'lil mouse engines, we count on high end Hp, rather than drag racing out of corners to win! Also all those pins add unnecessary weight!
{The above is all tongue-in-cheek for RJ!}
 

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Richard Jemison
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flywheels

The 1300/1600 did not use pins but a extra collar of metal on the flywheel to circle the PP and center. No pins, just mass.
 
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