New flywheel & clutch - Rebalance Y/N ?

[Moto]

I'm planning to replace the flywheel on the crossflow with a lighter steel item but am being given conflicting advice as to whether the crank with flywheel & clutch will need to be rebalanced together before re-fitting.

TTV (the flywheel supplier) say not as their new flywheel is supplied fully balanced. Others say I should do.

FWIW the existing unit was fully balanced when rebuilt 4 years ago.

Obviously if not required it's a 4 hour job that I can do myself. If the crank needs to come out it's a much bigger job with the need for the engine to be taken to a specialist to do the work.

Any advice?

Moto

[Dollyman1850]

Moto said:

I'm planning to replace the flywheel on the crossflow with a lighter steel item but am being given conflicting advice as to whether the crank with flywheel & clutch will need to be rebalanced together before re-fitting.

TTV (the flywheel supplier) say not as their new flywheel is supplied fully balanced. Others say I should do.

FWIW the existing unit was fully balanced when rebuilt 4 years ago.

Obviously if not required it's a 4 hour job that I can do myself. If the crank needs to come out it's a much bigger job with the need for the engine to be taken to a specialist to do the work.

Any advice?

Moto

It depends. If it is a zero balanced item and balanced then supplied as a unit to fit then No. If you are racing to fine tolerances and you want to ensure it is all at Zero with clutch bolted up then yes. For most day to day cars and part time motorsport then if a clutch is added it won't ,ake much difference,, Balancing much more critical on items where things have an out of balance and this figure changes with different pistons and connecting rods etc.. For a crossflow I would say the requirement is no.

[Moto]

Dollyman1850 said:

It depends. If it is a zero balanced item and balanced then supplied as a unit to fit then No. If you are racing to fine tolerances and you want to ensure it is all at Zero with clutch bolted up then yes. For most day to day cars and part time motorsport then if a clutch is added it won't ,ake much difference,, Balancing much more critical on items where things have an out of balance and this figure changes with different pistons and connecting rods etc.. For a crossflow I would say the requirement is no.

Yes it's supplied zero balanced so that makes life much simpler. I'm definitely at the "day to day car and part time motorsport" level so I should be OK then.

Moto

[anonymous-user]

Moto said:

Yes it's supplied zero balanced so that makes life much simpler. I'm definitely at the "day to day car and part time motorsport" level so I should be OK then.

Moto

Is that zero with the clutch fitted though?

[Moto]

V6 Pushfit said:

Is that zero with the clutch fitted though?

No that's the bear flywheel balanced without the clutch?

Moto

[anonymous-user]

Moto said:

No that's the bear flywheel balanced without the clutch?

Moto

You should really have it balanced with the clutch fitted, then it’s ‘zero’ so you’ll know any unbalance with the engine is damped without being added to.

[Moto]

V6 Pushfit said:

You should really have it balanced with the clutch fitted, then it’s ‘zero’ so you’ll know any unbalance with the engine is damped without being added to.

So 2 opposing views then

I'm leaning towards Neil's opinion as if you take your normal car (Ford Focus to a Porcshe 911) for a new clutch, they wouldn't take the crank out to rebalance it all. Would they?

Moto

[anonymous-user]

Moto said:

V6 Pushfit said:

You should really have it balanced with the clutch fitted, then it’s ‘zero’ so you’ll know any unbalance with the engine is damped without being added to.

So 2 opposing views then

I'm leaning towards Neil's opinion as if you take your normal car (Ford Focus to a Porcshe 911) for a new clutch, they wouldn't take the crank out to rebalance it all. Would they?

Moto

If you’ve got it off and in your hand you might as well do it, plus you don’t know what state of balance the engine is in.

Edited by anonymous-user on Wednesday 20th July 23:11

[Dollyman1850]

V6 Pushfit said:

Moto said:

V6 Pushfit said:

You should really have it balanced with the clutch fitted, then it’s ‘zero’ so you’ll know any unbalance with the engine is damped without being added to.

So 2 opposing views then

I'm leaning towards Neil's opinion as if you take your normal car (Ford Focus to a Porcshe 911) for a new clutch, they wouldn't take the crank out to rebalance it all. Would they?

Moto

If you’ve got it off and in your hand you might as well do it, plus you don’t know what state of balance the engine is in.

Edited by V6 Pushfit on Wednesday 20th July 23:11

Hence a complete waste of time balancing a clutch on a zero balanced flywheel.. If you were building a lightened and balanced engine from scratch you would balance the damper, crank, flywheel and clutch as 1 unit with known bob weights which take account of total piston, gudgeon, ring and rod weight on your balanced componants. If you are chacing minutia then you would get the flywheel spun up with the clutch attached but in reality clutches are well made these days and likely as not the differences are tiny. In my mind not to justify the expence not least of finding people these days to do it. Sling it all together it will be fine.. Like we all used to do in the 80's when just running and maintaining these cars.

[anonymous-user]

I have the advantage of a nearby bloke in a tumbledown shed at the back of a scrapyard who does balancing lightening porting and knife edging.

I wouldn’t know where to go otherwise.

[Moto]

V6 Pushfit said:

I have the advantage of a nearby bloke in a tumbledown shed at the back of a scrapyard who does balancing lightening porting and knife edging.

I wouldn’t know where to go otherwise.

Cheers chaps.... decision made. I'm definitely an 80's type guy.

Moto