Flywheel lightening.

[piman]

Hello all,

has anyone any knowledge of how much can be machine off a MK2 flywheel to improve engine reponse. I understand that it is steel and so should be capable of having a decent amount of metal removed. Ideally dimensions to work with would be excellent?

I am making progress now with my rebuild and the shell is currently away being sand blasted and epoxy primed after all the welding has been done. A couple of pictures during that work, typical MK 2 rust.

Alec

[Tom1]

Hi
I’d be cautious in relation to lightening your flywheel. The weight of a spring clutch assembly is approximately 12kg and you will only lighten your flywheel by 1 or 2kg at most. Better all round to fit a diaphram clutch which is much lighter and a more worth while upgrade.

[piman]

Hello Tom,

I intend fitting a diaphragm clutch, but it is not overall weight that counts but weight times the radius, in other words weight from around the periphery is more effective than from the centre. I would also think that much more could be removed than one or two kilos?

Alec

[Tom1]

Hi Alec
Noticed an aluminium flywheel advertised on eBay the other day £450 in e type spares.
I was advised against lightening the flywheel for general road use due to fluctuating /unstable idling. I believe that the mass of the flywheel is critical to the engine design and its behaviour when coming off the throttle. Sure it will spin up quicker but I doubt the benefits will be worth the trouble unless you plan on track use. The standard clutch assembly almost covers the entire surface of the flywheel there maybe smaller/lighter racing clutches available.
From the back face of the flywheel you can machine between the crank mounting flange and the ring gear only. There must be no sharp shoulders and the rebate should be blended in with large rads to avoid fractures. You must not reduce the thickness of the flywheel to any less than 10mm. Crack test/X-ray the flywheel first. Remember that the flywheel is cast iron and should the flywheel shatter at high revs the failure will be dramatic! Probably breaking your crankshaft too.
Good luck

[piman]

Hello Tom,

yes I am aware of those factors. Small diameter racing clutches are available but that is not the way I want to go.
There seems to be some difference in opinion as the the flywheel materia? I think it was the workshop manual that said it was steel, obviously stronger than cast iron, with an integral ring gear. Perhaps that is dependant on the year of manufacture? I will be able to definitely determine that once I start machining as there is a distinct difference between steel and cast iron, if the latter I shall be more circumspect. Des Hamill in his book also gives the 10 mm as a minimum thickness but suggests that a halving of the weight is possible?

Alec