Engine balancing.

[dougal9887]

What are the thoughts on the desirability of having this done for a road engine? Standard rev limit.
I ask the question because the engine I'm about to build up was previously balanced, but I'm changing the flywheel and coverplate. The pistons are already out having been machined. So the crankshaft could come out if the desirability level was high. If there is no real difference, and bearing in mind max revs would be occasional, I wouldn't bother. It's now or never!
Dougal.

[512BB]

Good morning Dougal,

I always bother when I am building a twincam motor, to balance.

In my opinion, a 4 cylinder engine is never going to be as smooth as say, a BMW 6 cylinder engine, so for me, I want it to be as smooth as I can possibly get it. I drive quite a few miles in my cars per year, so if the engine I was building was for use in a car that I owned, I would want it smoooooth.

Now wether you can tell if a 4 cylinder motor has been balanced or not, I do not know. I suppose the ultimate test would be to drive a car for say, 1000 miles before the engine was balanced, then remove engine, balance, and drive again, and see if you can deduce the difference.

All I can say is, every little bit helps.

What I am looking for, in my next engine build, is the guy who does the actual balancing, not the firm who just adds 100% mark up to his bill.

Leslie

[john.p.clegg]

If you're anywhere near these...

http://www.bassetdownbalancing.co.uk/

I'd recommend,they did my matchless/A65 crank many years ago and it was a treat...

John

[nomad]

If one wanted just the flywheel and clutch assembly balanced after the engine is built would it be possible to have that done???

My engine builder says he only does it as an assembly with the crank.

Kurt

[512BB]

John, Thanks for the link, they certainly look as though they know what they are doing from their website. I shall give them a go, as they are about as far from me as Gosnay's, who I used last.

Kurt, If you look at your flywheel, you will see that it has more than likely been balanced already, individually, look for holes around the circumference, as will your clutch cover. So just doing them again without the whole rotating assembly would, in my opinion, be a waste of time, and money.

Leslie

[bigvalvehead]

I believe that the correct sequence is to balance the crank on its own, bolt on the flywheel, rebalance only removing material from flywheel, bolt on clutch, rebalance only removing material from clutch, bolt on crank pulley, rebalance only removing material from pulley.

That way each component is balanced individually but the whole rotating assembly is in balance.

Dave

[nomad]

Yes, I'm familiar with the sequence and how they are balanced at the factory but, without thinking about it I built my engine before considering that I needed a new ring gear. On my flywheel the ring gear was tack welded in four places. Weld to cast iron did what one would expect and broke out sizeable pieces when I removed it. I fitted a new ring gear and replaced the tack welds but any imbalance on the periphery of a rotating mass like that concern's me. Wish I had thought about it before.

Kurt.

[oldchieft]

Never miss the chance to get everything as well balanced as possible.

You will almost certainly regret not doing it later.

Jon the Chief

[AHM]

Rohan has posted in the past about balancing.

I followed his comments got all of the rotating parts professionally balanced and matched and balanced rods and pistons myself to within 1 gramme - You will notice the difference!

[elj221c]

If one wanted just the flywheel and clutch assembly balanced after the engine is built would it be possible to have that done???

My engine builder says he only does it as an assembly with the crank.

Kurt

Not that I have used my engine since I had all the components done by QED, so I don't have proof....

However, when I asked about balancing they said....

Crank and rods done. Flywheel done. Doesn't matter where flywheel bolted, it will all be OK as that is done too, on its own.

It's a road engine but I quess they knew what's what for that.

As for welding the ring gear.....? Change your machine shop?

[nomad]

Roy the ring gear was welded in four places when I got the car. I would almost think it was done at the factory!?? Ring gear was extremely worn and the engine bores were stock and had very little wear. Don't have the speedometer or much history other than that.

Kurt
26/3754

[pharriso]

Roy the ring gear was welded in four places when I got the car. I would almost think it was done at the factory!??
Kurt
26/3754

I've not heard of ring gear being welded on. Standard assembly method is to heat up the ring gear (not too hot Ed) & then it cools to a tight fit on the flywheel.Perhaps belt & braces by someone? You can't really weld the cast iron flywheel anyway

[nomad]

Yes, Phil, I thought it looked like a shoddy way of doing things myself. The four weld's were well done but not with nickel rod. I tried to replicate them with nickle after I had heated and shrunk on the new one. Just to try to get the balance back if for no other reason.

Kurt.

[StressCraxx]

Some engine builders tack the ring gear to the flywheel after shrinking it on. This is really common if you have a motor with lots of timing advance that may kick back on the starter when cranking. If the motor is hard mounted to the chassis, tack welding helps prevent the ring gear coming off.

[nomad]

Some engine builders tack the ring gear to the flywheel after shrinking it on. This is really common if you have a motor with lots of timing advance that may kick back on the starter when cranking. If the motor is hard mounted to the chassis, tack welding helps prevent the ring gear coming off.

That explains it....but I'm still a little concerned about balance!

Kurt