Gday all, just wanting some insight to lightened flywheels. Can you go too light? There are some lightened flywheels which are "not recommended for road use" why is this? What would happen if you put a really light flywheel onto a road motor? that's worked obviously..... Cheers fellas

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1964 smooth roof panel van
1967 Mk 1 X-Police cooper s
1970 mini k
1975 leyland

One of the reasons for having a flywheel is for maintaining momentum when an engine is at idle & if too light a flywheel is fitted the idle will constantly be speeding up & slowing down from compression/power strokes & will run very lumpy, which in a street car will not be very pleasant at all, but a race engine needs to rotate a lot faster & is rarely at idle so it needs a light flywheel. Others might help explain it further as well in case of other reasons I've forgotten since I went to trade school.

Brad

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During the day I work on English designed cars & on my own time I work on English designed cars....

Can you go too light?..

IMHO - no. I've run an 8lb Manx Racing flywheel ..and matching lightweight backplate on my road car for years (decades in fact).

Maybe you have to get used to driving it ..but I couldn't say. The only other person to drive my car - the mechanic who does the annual brake test doesn't seem to have an issue either.

I guess the only downside I can think of is the thin ring gear ..although I'm not really sure the thinness is the real problem but I have had to replace it. The engine was a bit lumpy with a 286 but the current 731 idles quite smoothly at under a thousand revs..

Cheers, Ian

I was looking at buying a lightened flywheel and saw the lightest one that "is not recommended for road use" and I though it'd be best to get but if my car won't idle or run properly it's not worth getting..... Anyone else have experience in a very light flywheel?

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1964 smooth roof panel van
1967 Mk 1 X-Police cooper s
1970 mini k
1975 leyland

What Brad said. Rougher idle, and more revs required for takeoff. On the good side is a faster revving engine.

Don't do a diy machining job. Flywheel failures are fairly spectacular. A look at where the flywheel runs relative to the driver is fairly sobering.

So it would be OK for a road car just lumpy idle as if you had a race cam? No it wouldn't be a home job it would be bought from a mini shop and the lightest one I can find if it'll work

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1964 smooth roof panel van
1967 Mk 1 X-Police cooper s
1970 mini k
1975 leyland

Maybe not "lumpy"...just easier to stall on the road...you have to remember that they made the flywheel a particular weight for a good reason in the first place and as a compromise between outright performance and tractability...for example, it means when you are bringing up the clutch in a road car trying for a nice smooth change that it will do that.

Get some good advice on the optimum weight for your engine tune/clutch type etc...

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"Show me the Mini!"

No, not lumpy at all - in my experience...

However, yes, it does take more care to drive... but BMC... Rover et al built cars for the masses ..And you have to remember that half the population is of below average intelligence .and ability..

Cheers, Ian

You can run the ultralight flywheel with a stock eg Cooper S backplate for a road car. Will still be much lighter than stock.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Some light flywheels come with integral ring gear... i expect they will be the ones suggested not for road use
When the ring gear is stuffed from multiples of starts with road use & crappy 2nd hand sh1t starters you have to either machine the ringear off & sweat/pin &/or weld a new ring gear on it would be a pain in the arse
In saying that ... we all generaly take care of our starters & ring gears these days dont we?

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Matt if running an ultralight one I would use a pre-engaged starter. Gemini or better. Not ye olde Lucas.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Only half?....Don't a lot of the ones below average intelligence and ability usually just give up and join the services where they can always rely on having someone around to tell them what to do

(PS in the olden days it was often the Magistrate who encouraged miscreants to "join the Navy" ....or else)

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"Show me the Mini!"

Steel ones can weld themselves onto the crank and can be a pain to remove.
I use lightened cast ones, not greatly machined down, in both my road cars along with sturdy scatter shields fitted to the housing. Never had a problem with these.

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Slide
1965 Mini Van (1360)
1970 Mk2 Cooper S (1310)
1978 Rover SD1 V8 (4.6)
1996 Land Rover Discovery V8 (4.0)

Im running a lightened med flywheel and intermediate plate on my motor. It is close to 13~1 compression 286 cam lightened balanced x drilled and nitrated crank. Revs like a dream all the way up past 8000rpm(very rarely) but yes requires extra revs too take off and stalls below 1000rpm idle.

Im used to it now as I drive my mini like I stole it.

Combined with the heavy duty pressure plate its a ning nong in heavy stop start traffic.

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

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"Show me the Mini!"