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Accurate balancing of crank, then fw, then the pair and the clutch too sometimes is vital or it may burst.
I am not going to state anything definite here but the highest rpm I recommend on a cast iron fw (all of them are cast on OE units) is say 7500 on the 2 liter and maybe 8000 or so on the lighter 1585 one. Over 7200 I definitely recommend dowelling to stake the shear stress off the bolts alone.
I'm not into numbers in a big way, there are variations in weight on the 2 liter and similar 1800 fw, what you see here is my typical target weight for the 2 liter, The outer diameter that hold ring gear and bolts is not machined. Attention to generous radii is very important, there are only two regions inner and outer that need them so get them right! Don't go close to the drain holes in the centre region because on the other side there is an undercut and it will weaken it severely. It's not a bad idea to spray paint the machined region as it will rust very quickly in-situ.
The fw is machined for lightening by holding in a 3 or 4 jaw lathe chuck and accurately centring on the locating diameter in the centre that sits on the crank end bearing (RWD) or bush (FWD and 4WD).
The fw is overhauled by grinding the friction face and then machining the 20thou" step for the clutch cover.
You don't have to run a conventional OE type clutch - the cast fw can be safely remachined for say, a Ford clutch, 7 1/4" race clutch etc. but make sure bolts have 1.5 x bolt diameter thread engagement, and conventional clutches must have dowel location. If changing the bolt array, it is vital to have the clutch balance checked on the crank fw pair.
Pictures below hopefully self explanatory.
- Lightened Fiat 2 liter FW_01.jpg (114 KiB) Viewed 11073 times
- Lightened Fiat 2 liter FW_02.jpg (103.32 KiB) Viewed 11066 times
- Lightened Fiat 2 liter FW_03.jpg (82.73 KiB) Viewed 11057 times
- The white stuff in the holes is Loctite or similar, often seen but NOT needed, don't use it..
- Lightened Fiat 2 liter FW_04.jpg (92.25 KiB) Viewed 11049 times
- Don't even think about using a new clutch on an old friction face! You'll lose 20% of your new clutch lining within the first 50 miles. if the fw is reground - GET IT BALANCED with crank!
- Reground Fiat 2 liter FW.jpg (98.57 KiB) Viewed 11059 times
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