Engine Balancing - what's involved?

[philwaters]

How does one go about balancing an engine? How much would I have to strip down and more importantly what are the 'real-world' benefits that you'd actually notice?

 

Idle thoughts on a Friday afternoon having just taken a colleague out for a blat in the sun

 

Phil Waters

[I.Mupferit]

Don't Nicholson McLaren balance engine parts Phil?

 

Seriously though, I doubt that any small benefits gained from balancing the crankshaft/rods/pistons/flywheel/clutch cover would be worth the aggro on an engine used in our sort of application, especially when it is still in the car and working well.

 

Might be worth considering if the engine was already in bits and being rebuilt but other than that, I wouldn't bother.

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

 

 

 

Edited by - Brent Chiswick on 3 Aug 2007 14:31:47

[Sheds Moderator]

You can only do it with a totally stripped engine and it allows you to rev higher, all other things being equal. Basically you have to weigh all the pistons, then the piston assys, then put them on the crank, dynamically balance that, probably the camshaft too, then fit flywheel, balance again, etc. IMO it's only of benefit if you have to have a particcular engine spec (so are looking to shave an advantage off your colleagues) or you are truly licking the stamp of the performance envelope.

 

More gains are availabl from "normal" tuning.

[oilyhands]

You can only dynamically balance rotating components, reciprocating components like rod and piston assemblies are balanced off the crank set, but not only for overall weight but for weight over each end of the assembly. Quite often the fit of components to the crankset, E.G. flywheel/clutch and pulleys is not ideal and that can lead to quite large imbalances, especially if the flywheel has been fitted to the engine after the balancing has been done, as is the case for most 1800K Caterhams and any Caterham that has a lightened flywheel.

 

You would be surprised just how far out the standard cranksets are when the imbalance in the flywheel anc clutch diaphragm is taken into account. If you are fitting a repalcement flywheel/clutch assembly it is worth having it balanced on a drone crank before fitting and ensuring that it is bolted on with the crank in the same postion as it was when bolted to the drone crank.

 

Secondary out of balance forces are a whole different ballgame since you are dealing with the difference in mass between the crank pin/rod/piston assembly and the crank counterweight. Secondary OOB forces can be as much as 1500KGs at 8500 on a steel k series crank with the typically small counterwights.

 

Oily

[Tom_C]

There was a good artical about this in Full Throttle last month, by Dave Walker IIRC. Apparently engines can be balanced in the car if necessary...

 

BTW please give generously to Bundle's Big Charity Walk for Asthma research here Ta.

 

Cheers

 

Tom

 

FH54WLX

 

see here - UPDATED again

[Andy Best]

I must admit I was unsure about engine balancing, Oily gave some input as did a number of other owners who had built/rebuilt engines. I understand that an engine can only be balanced properly when its in bits. Its the bits that go round pullies, crank, flywheel and clutch cover and the rods and pistons that need to be balanced as individual items and then as a set. The assembly also has to be undertaken carefully to ensure the bits are put back together in the correct orientation to each other to maintain the balance achieved.

 

After my research I decided that my engine would be balanced by Vibration Free and assembled by Oily. The work was not cheap but when considering the time that goes into the balancing and assembly fair.

 

Although I have only done 800 miles with the engine there are noticeable improvements over the old engine, very steady idle, smoother response both during acceleration and deceleration and the gearbox is a lot more quite in neutral and off the gas motoring. All this has been achieved so far without a proper Emerald map I hope I am still as happy after my visit to Dave Walker in September 😬

 

Was this as a result of the balancing and build or some of the other bits that got added 🤔 The truth is I don't know, but I am certainly a lot happier with this engine compared against the old one.

 

I doubt I would take an engine apart just to balance it but as part of a wider upgrade refresh plan I wouldn't hesitate to have an engine balanced and assembled correctly in future.

 

Andy

[Paul McKenzie]

It's vital 😳. Would you put a new tyres on your front wheels, and say to the fitter, I won't bother with the balancing if you knock off £2 a wheel - guarantee you'd be back after 20 miles?

 

Proper balancing is essential for any engine, particularly a tuned engine..it revs more freely is just so much smoother

 

Paul

[David Ward]

Also had my 1900 K balanced by Vibration Free and assembled by DVA. That seems to have coincided with a trouble free race season so far with a hard used car and a heavy right foot! I'd certainly recommend it, especially for a more enthusiastically used or tuned engine.

 

Dave

Kept meaning to email you to tell you it's still going like a rocket after 4 busy race meetings and a lot of road miles this year! Cheers

 

V7 HPD

 

[oilyhands]

Hi David,

 

Glad all is going well

 

Oily

[philwaters]

Thanks all - something to ponder.. not sure my fairly basic spec is worth ir, or worth taking apart by the sounds of it.

 

Unless..... mmmm 225bhp???

 

Phil Waters

[McBreadhead]

So would balancing be of cost-effective benefit for my 160bhp xflow, currently in bits awaiting re-bore, rebuild etc? Predicted rev limit will stay at 7,250. How much roughly would it add to the rebuild?

 

Thanks.

[blade_runner]

Can anyone recomend a place to get a RRW Blade engine balanced? my old engine was An Ex motopower firehawk race lump, as built my RST V8 Russell,s old team, the crank was balanced, and the shell bearings were different to standard with each journal cap being indivually set. ie not all torqued up the same, each bolt was engraved with a number, which matched up to a number on the casing, then each bolt had a centre punch mark to line up to one on the casing. this was supposed to be where it made a lot of its extra power from, apart from a highly modifyed head. and allowed it to rev to 12200 rpm's it made peak power at 11800, standard blade peak power is about 10500, rev limiter 11500.

I have sitting in the garage a standard engine i'd like to try and get to the spec of the orriginal, so need the bottom end worked on, then i can replace the couple of bent vavles on the old head and attach to the new bottom end. looking for someone in the east of england area.

 

'Pinky Pics' here

[blade_runner]

 

'Pinky Pics' here