Lightened flywheel

[Classic Chim]

I see an add on Facebook for RV8 flywheels lightened and balanced down to about 9 kg.

My engine has about 340 ft lb torque and about 300 Bhp
What benefits should I expect from such a light flywheel
What downsides will there be.
Where there is a + there has to be a - so let’s be straight and talk of any potential issues arising from using a light flywheel on the roads aswell as the benefits.
Thanks in advance.
Winter so it’s worth talking tuning mods

[Classic Chim]

Thanks boys, pretty much what the science of lighter suggests.
The real question is will I shave a few tenths of my drag strip time remembering it’s a blistering 12.60 as it is

So the standard flywheel must be about 16kg’s and these lightened one’s 9kg so knocking off nearly half its weight which is a big difference.

My concerns are as Boosted pointed out, I might loose my lazy smooth as silk engine that’s really enjoyable to drive at slow speeds.
My MBE Ignition and fuelling is exactly how I like it as in you shut off and it’s off, no pops or bangs until down to 1700 then loads of them as mapped in but again requires a touch of throttle to activate, it’s like pops on tap
This is just fantastic on track and anywhere where you just want throttle control to slow you slightly, engines been rebuilt by Dom so full of compression anyway so de acceleration needs to be done quite carefully anyway even with the heavy fly.
Hmmm
I’m bloody going off the idea already. Seems a cheap and fairly easy mod if it brought a few benefits mind. 2/10th of a second would be nice

Edited by Classic Chim on Wednesday 29th January 10:39

[Classic Chim]

Zener said:

Alun you need to check what you have fitted 1st already witnessed a 450 with the bespoke TVR but cast iron lighter FW about 8.5 kilo's IIRC, the other thing is unless your existing FW is set at a neutral balance you will undo Powers work (speak to Dom) I use a steel 6.5kg FW and this will make for a loapier idle and will not improve low speed manners may not be much worse but even so not beneficial either (gear shifts are fine ) getting away quickly is an all or nothing deal but mastered after a short while but I have less CC's and more cam than you so not totally applicable would I go heavier? ........ NO definitely not its part of the whole character of my engine and works , looks nice though dinit ?

Edited by Zener on Wednesday 29th January 12:11

dinit indeed.

I’m pretty sure Dom will tell me to leave it alone,, I’ve asked him before. I’ll check with him again, maybe I can talk him into letting me have it
I’ll mention 2/10ths, he’ll scoff and say drive it better He will honestly, takes no st off me
Cheers guys
I think I’ll leave it until I’ve at least driven my car after chassis work.
Is it easy enough to replace fly in situ at a later date. I’d like one real bad
It would encourage me to finish porting my heads...

[Classic Chim]

Just been looking at the JE ones.

The ones a saw advertised come from the states I believe.
It was just a thought provoker as I’d buy a british one and JE are just round the corner

I’ll talk with Dom.

[Classic Chim]

Zener said:

John Eales will machine a customer FW for around 80/90 squids IIRC that one in the pic is an example , gave it to my brother for an Xmas gift years ago got him guessing

Cracked me up,,
Your a good brother you are

Right now I know Anthony’s car and others including Peters( though I doubt the flywheel has much to do with the insane power output) all have lightened flywheels this bit about it revving or spinning up quicker, I can l tell when I drive mine it lags slightly on that spin up compared to these cars.
Once it’s revving and flat out I think it helps balance my engine and actually pulls better at higher revs compared to say a 5.0 which vibrates like mad in comparison, or the ones I’ve been in do. I hardly ever go to 5000 revs though so through the ranges I use it should be spot on.
I’ll contact JE and see if he’d like to lighten my fly. I might still bottle though, it’s not a slow car by a long way, I happen to be judging it up against the fastet 5.5 Chim in the world and Anthony’s which has a Matt Smith allover it, Zener: his has heads as big as a Chevy quality cars of speed.

Basically if I don’t do something about it Jacko Jackson4 with his alarmingly bright and very fast yellow 5.0 is going to stuff me up the drag strip everytime.

Edited by Classic Chim on Thursday 30th January 00:41

Edited by Classic Chim on Thursday 30th January 00:43

[Classic Chim]

TwinKam said:

Just buy Peter's car, Alun, and I'm sure he'll throw in his lightened flywheel 'for free'

I’ve driven it flat out once, out the back at Bedford so Peter didn’t see me came past the pits all pedestrian like then nailed it again
Too fast, it was slower then than it is now,,,,
Proper, still locked it up though, really quick effortless car to drive with the Scooby rack.
Imagine what it’s like to then drive my own, I’ve been chasing cheap power ever since

Edited by Classic Chim on Thursday 30th January 00:45

ETA I remember now, 140 mph down what isn’t the longest straight before the fast ish chicane, overtaking MX5 and Boxsters like they were standing still, I get it now, track days allow you to crush others dreams,,, including mine when I had to drive mine home
Seriously fast car above 100 mph let alone before that.

Edited by Classic Chim on Thursday 30th January 00:55

[Classic Chim]

Thanks for all this useful advice lads.
So do I need a special puller to remove my old one?

So steel is the way to go. Ok.

[Classic Chim]

Zener said:

ope no puller needed, I would however renew the FW bolts but thats just me I went ARP available and cheap from Realsteel the steel FW is an interference fit on the crank raised spigot bearing housing/Tit this is a feature of this kind of unit and in the literature anyways just though i'd mention

[Classic Chim]

So on the RV8 it has two end weights,
1 the front pulley
2 flywheel +clutch.

My front pulley wheel is balanced as is my flywheel.

A known reputable lightened flywheel will be balanced too I assume so this should not effect my cranks balance.
I don’t want to knock out what is a new bottom end on my car. A lightened flywheel must surely be centre balanced when made so should be ok to use.

Does this sound correct.

Can someone calculate the gains achieved over a 1/4 mile using a 8.5 kg one roughly from the standard 14 or possibly 16 kg as I don’t know what mine weighs
If it’s like 3/10th of a second it’s getting done

I’ve had the go ahead boys,,,,,,,, : thumbup:
Trouble is another mod that will knock 1k off the sale price come the day,,, 3/10ths though that’s like the holy grail to me

Edited by Classic Chim on Thursday 30th January 13:50

[Classic Chim]

Boosted LS1 said:

In an ideal world the engine will be internally balanced and the flywheel and damper will be neutral balance. This means they can be swopped for other neutral balanced parts without upsetting the engine. Same goes for clutch packs I imagine.

On some engines (ls vettes) there will be some additional fine balancing of the damper and flywheel which contributes to an extra 500 rpm's. The camaro's don't have this luxury. :-)

I watched an old time video of Jaguar production once, cranks being balanced so would the RV ones be balanced as an individual item long before it went in an engine.
If so as long as I get a balanced flywheel I should’nt have any problems, shucks MAC had one so it must be right

[Classic Chim]

Dominic TVRetto said:

No it doesn't, I'm afraid...

CHECK WITH DOM - I was looking at doing this a few years ago, engine rebuilt by Dom just like yours....

Entire rotating assembly had been balanced by Dom as a single piece - so simply switching the FW over would throw the whole thing out of balance, with disastrous consequences...

If Dom did it the same as mine, you will need to take it the FW/crank /pulley combo from the block, change the FW and get the whole thing rebalanced - then reinstall. Big money.

Also, doesn't look like anyone's mentioned that a lighter flywheel will increase engine braking - for what it's worth...

HTH,

Dom

He’s often put me off the idea?

There’s no question the engine vibrates less at high revs than it did before he rebuilt it or that’s always been my perception at least.

I’m not sure what I’d gain in the real world as I’m a plodder on the roads.
Don’t get involved with boy racers so other than a few Hp gain a bit like my baffled sump, nice to have but somewhat pointless.

Any thoughts on this from guys with rebuilt engines who just put a lightened flywheel on.

[Classic Chim]

phazed said:

Never noticed any increase in engine braking although if it's marginal I wouldn't have noticed it.

I have heard of people who lock up the rears when changing down, more engine braking compared to a 4 pot. I always heal and toe so have never had a problem.

Well this is another thing,,, I have a lot of engine breaking, I’d lock wheels everytime without blipping the throttle,,,

Not sure what to make of all of this. Surely a flywheel needs to be balanced as part of the complete thing or is it the case of if the flywheel has been centrifugally balanced it’s ok to fit.
If I do this I want John Eales to do it as it keeps it all close to home.
Ill make more calls

[Classic Chim]

Boosted LS1 said:

Yes. As far as I know the rover cranks were balanced as a job lot elsewhere because they already knew the appx weight of the reciprocating and rotating components. Once the engines were assembled they had 2 machines at the plant which could spin them up to check for irregular vibrations. The red line on a rover is 5500 iirc.. If they needed to correct anything they could add weight to either end of the crank but I imagine that would be quite rare.

If these cranks were balanced by LR would we not see witness marks on the counter weights or drill holes etc. Has anyone ever witnessed markings or weights maybe?
If not then it would have to be done with pulley and flywheel as a complete mass I presume which means sticking on another flywheel might well knock the balance off or am I misunderstanding this.

[Classic Chim]

phazed said:

I believe the original engine is balanced, flywheel, crankshaft and front pulley together.

You will probably find that your later rebuilt engine by Dom has items balanced individually.

I’m not being dis encouraged but I’m not being encouraged either really.
Dom has said if it’s a good one well balanced it would be ok but I think his balancing outways what I’ll gain from this.

I’ve decided to err on the side of caution for now.
My engine has a very sweet balance and effortlessly drives down to extremely low revs if needs be with no shunting then hits the limiter with no vibration at all, it’s already very efficient.
If I just replace the heads it’s a 320 Hp engine all day. It’s got great torque for a 4.6 and frankly I love it as it is.
I secretly love its lazy nature too.
I have a competitive spirit ( mainly cos it’s fun now rather than winning at all cost) so would dearly love to shave a bit off my 1/4 time then retire a happy man
A fly seems an easy way to do that but that’s all, I don’t need another 10 Hp or I’d get my heads worked.
If my engine had not been rebuilt by Dom I’d put one on so I think it’s a good mod but in view of the fact my bottom end has been rebuilt and it runs great I’m not risking it.

Thanks for all posts and information shared.