18 replies to this topic

[_mini1000_]

im looking into adding a lightened flywheel to my 998 engine
what would be the drivability be like with an 11 lb flywheel http://www.minispare...id=32795&title=
compared to a 8 lb flywheel http://www.minispare...id=35440&title=

[Cooperman]

With the lighter flywheel it will accelerate better.
However, it will not be as smooth until it gets up on the cam and the tickover will need to be a bit higher.

[bmcecosse]

What other mods have you done to the engine ? While a light flywheel is a delight - it's really only at it's best on a highly modified engine - otherwise the benefits don't really justify the cost.

[minimender]

Why not get your own flywheel and backplate skimmed at an engine re conditioners.

Save some money and get em both done.

[cooperrodeo]

I purchased a lightweight flywheel from Minispares and it weighed just under 10lbs. What surprised me when I made the change was that the previous flywheel, which I had thought was a bog-standard one, weighed 12.75lbs which was nowhere near the 22lbs quoted in the Minispares blurb. So, before rushing out and buying a new flywheel, I suggest you weigh your existing one and then make an informed decision.

[_mini1000_]

What other mods have you done to the engine ? While a light flywheel is a delight - it's really only at it's best on a highly modified engine - otherwise the benefits don't really justify the cost.

its got a sw5-07 cam with a cooper head running a 10:1 cr with dished pistons

I purchased a lightweight flywheel from Minispares and it weighed just under 10lbs. What surprised me when I made the change was that the previous flywheel, which I had thought was a bog-standard one, weighed 12.75lbs which was nowhere near the 22lbs quoted in the Minispares blurb. So, before rushing out and buying a new flywheel, I suggest you weigh your existing one and then make an informed decision.

thanks for the heads up
i may get the scales out and see what im working with

is there a safe limit/weight that the standard flywheel can be lightend to?

[twrminisport]

Change the cam first. Theres no real point in putting a lightened flywheel on a sw5-07. Pull it out and put a 276 in there or a 286.
Im assuming this is a 998 motor yeah?
With this sort of cam a lighter flywheel will make a differerence. Without this sort of spec your money is better spent on the cam change.

Edited by twrminisport, 13 August 2011 - 10:04 PM.

[_mini1000_]

Change the cam first. Theres no real point in putting a lightened flywheel on a sw5-07. Pull it out and put a 276 in there or a 286.
Im assuming this is a 998 motor yeah?
With this sort of cam a lighter flywheel will make a differerence. Without this sort of spec your money is better spent on the cam change.

yea its a 998 engine
its just after a complete overhall with whatever needed replacing replaced.
i want to keep with drivable with a smooth idle with the low down pull which is what made me go for the sw5-07

someone mentioned that i would need to balance the rods/crank etc or else the engine would shake it self to bits. is this true for a 998 or more so for engines putting out bigger power/torque?

[mike.]

Change the cam first. Theres no real point in putting a lightened flywheel on a sw5-07. Pull it out and put a 276 in there or a 286.
Im assuming this is a 998 motor yeah?
With this sort of cam a lighter flywheel will make a differerence. Without this sort of spec your money is better spent on the cam change.

yea its a 998 engine
its just after a complete overhall with whatever needed replacing replaced.
i want to keep with drivable with a smooth idle with the low down pull which is what made me go for the sw5-07

someone mentioned that i would need to balance the rods/crank etc or else the engine would shake it self to bits. is this true for a 998 or more so for engines putting out bigger power/torque?

Well the ultralight flywheels you can buy don't come balanced anyway, so if your fitting one of them you'll need to take it to be balanced. So usually people take the whole rotating assembly and get it all balanced up together.

[Cooperman]

Balancing is for very high-revving engines, so unless you fit a very 'hot' camshaft, balancing will achieve little except to make you a bit less wealthy.
Maybe you need to define what you want to use your car for, the type of journeys you'll be doing and how able you are at rte-building an engine yourself.
Then advice can be given based on the use of the vehicle.

[_mini1000_]

Change the cam first. Theres no real point in putting a lightened flywheel on a sw5-07. Pull it out and put a 276 in there or a 286.
Im assuming this is a 998 motor yeah?
With this sort of cam a lighter flywheel will make a differerence. Without this sort of spec your money is better spent on the cam change.

yea its a 998 engine
its just after a complete overhall with whatever needed replacing replaced.
i want to keep with drivable with a smooth idle with the low down pull which is what made me go for the sw5-07

someone mentioned that i would need to balance the rods/crank etc or else the engine would shake it self to bits. is this true for a 998 or more so for engines putting out bigger power/torque?

Well the ultralight flywheels you can buy don't come balanced anyway, so if your fitting one of them you'll need to take it to be balanced. So usually people take the whole rotating assembly and get it all balanced up together.

i would get the flywheel balanced with the back plate and clutch however someone mentioned to me that i would need to balance the whole assembly (crank, rods, pistons etc) or the engine would shake it self to bits?

Balancing is for very high-revving engines, so unless you fit a very 'hot' camshaft, balancing will achieve little except to make you a bit less wealthy.
Maybe you need to define what you want to use your car for, the type of journeys you'll be doing and how able you are at rte-building an engine yourself.
Then advice can be given based on the use of the vehicle.

thanks Cooperman
i should have provided more information in my original post
the engine is a pre A+ 998 with dished pistons, 12g295 cooper head, 10.1 cr, 3.44.1fd, sw05-07, hs4 carb with minispares inlet and freeflow exhaust
the car will be used mainly at the weekend but might eventually turn into my daily. i bought the car with the standard 998 and wanted to make it a bit more fun to drive/
the engine is only back from a rebuild with new main and big ends, gearbox bearings etc. (carried out by my local mini specialist)
my own knowledge of engines would be basic enough but my dad is an ex mechanic (over 17 years since he properly worked on an engine so im not too sure how accurate he would be either)
hope this helps

Edited by _mini1000_, 05 September 2011 - 11:24 PM.

[Cooperman]

With that spec very high revs will not be used as the cam will 'run out at about 6000 rpm maximum. A slightly lightened flywheel would be good, but not too light and it might be a good idea to just have your machine shop turn a bit off your existing one.
No need to balance as it's a 998 and they are smoother than the 1275,
I like your spec. I built a 998 into a 1061 cc unit a while back. It had a 295 head mildly gas-flowed and with 10.3:1 C.R., a 510 Cooper 'S' cam, an HS4 on a Howley manifold and an early 998 Cooper ex. manifold with RC40 small-bore exhaust system. The flywheel was slightly lightened and it had a re-curved distributor. Power was 68 bhp at flywheel and diff was 3.2. It was great to drive and very smooth.
Good luck with yours.

[b34k3r]

It depends on how street driveable you want it.. I opted to keep a standard weight on mine. I had a old Mk2 escort with a 1600sport with a very light flywheel and it was fantastic at high rpm, but a pig of a thing to get off the line without giving it a whole lot of RPM.if you have a big cam and a light flywheel it will just make it harder in heavy traffic.

[jaydee]

I've never heard good opinions about sw05 on small bore engines..thats why i'm stick with kent cams for my small bore engine..
I've just used the rally car as a daily today, i have lightened flywheel and the 276 and too be honest the lumpyness is not really a problem in the traffic, theres enough pull from very low revs to cope with the traffic.
What i really think should become a problem with daily use is the noise and the vibrations, car has no soundproofing so its a bit loud inside and the carb hit the bulkhead sometimes making an annoying 'knock' noise, lots of vibrations with the solid subframe mountings the exhaust hit the floor sometimes so extra vibrations added, etc..

Edited by jaydee, 06 September 2011 - 09:59 AM.

[Ethel]

A lightweight flywheel really only makes a different accelerating off the line, by the time you've got to 3rd or 4th taking the spare wheel out will have about as much effect. Even so, every little helps when there isn't lots of power to start with. I'd stick with that cam for a road going 998. The flywheel would only be making up some of what you lost by swapping to a wilder cam unless you thrash it everywhere.

What's the cost, it could be better spent on the ignition.