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Fiat/Lancia TC flywheel prep and lightening

Posted: November 23rd, 2006, 11:06 am
by Guy Croft
Mass removal from the flywheel improves throttle response, I cannot quantify what it is worth in accelerative terms, but it is common to do it on high rpm motors to do this. I would not go thinner that 10mm-12mm anywhere on the TC flywheel and I am not planning to publish engineering dwgs at present!

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.