Lightened flywheel

[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.

[phazed]

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.

[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.

[Boosted LS1]

Classic Chim said:

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.

If it's an externally balanced crankshaft then then replacement external parts have to be balanced the same as the original parts.
Years ago I saw dozens of rover cranks waiting to be balanced. Just the cranks on their own. They worked to very generous tolerances back then.

[900T-R]

I think TVR 5 litre engines (with their own crank casting) were externally balanced, but I could be talking out of my posterior here...

[Zener]

900T-R said:

I think TVR 5 litre engines (with their own crank casting) were externally balanced, but I could be talking out of my posterior here...

Correct 900T, SB Ford V8's were done this way too I consider it lazy and inferior, generally most mainstream manufacturers factory balancing is pretty good IMO not great but good , Honda was exceptional back in the day (cant comment on nowadays) even down to the clutch cover plate being indexed to the FW too from the factory replacement covers also had this mark

[Boosted LS1]

900T-R said:

I think TVR 5 litre engines (with their own crank casting) were externally balanced, but I could be talking out of my posterior here...

This would be because the counterweights have a smaller diameter to avoid crashing into the piston skirts at bdc. There just isn't enough mass left for balancing.


An interesting read which supports internal balancing.

https://www.enginelabs.com/engine-tech/taking-it-f...

Edited by Boosted LS1 on Saturday 1st February 00:05