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Practical Engine Building

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Discussion and questions related to the course Practical Engine Building

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Would you recommend balancing a lightweight billet crank as Manley made for 4g63? Also to balancing a Crank I understand than have to be balancing with harmonic balancer, flywheel and clutch, but what if you have a fluidamper or ATI damper and also double or triple clutch disc?


there is a few questions to ask here

is the engine built already ? if not yes balance it as a combination

if it is built do you have the old fly wheel ? most flywheels are zero balanced and any balancing should be done internal on the crank

so unless there is obvious weights or drilled balance holes you should be ok to bolt it on

you could get your local machinist to check it on there balancing machine

I think part of his concern is that some aftermarket dampers are reputed to be difficult to balance properly - IIRC, it is mentioned in the FAQs on at least one manufacturer, if you can't find it there, you could try an interweb search or their tech support?

With the multi-plate clutches, they would normally be done as an assembly, but check with the people doing the balancing for you for what they want. It will probably be any additional drive pulleys, too.

Hi guys, yes my question is for a new build engine.

What I understand Crank Balancing needs damper and flywheell, that that right? so aftermarket damper such as ATI or Fluidampr and Multiple Clutch disc do they won't reccomend using it to internally balanced engine, so in this case how would you balance the crank or balance the rotating assembly with those parts?

This is ATI Racing info:

Q: Can I use my externally balanced damper on my internally balanced engine?

A: No! Many people think you can simply remove the weight and the damper would be okay for an internally balanced engine. This is an incorrect assumption, however. Due to the design of the damper, when the weight is removed the damper will not function properly and could potentially damage your engine. Send your damper to ATI and we can convert your damper from externally balanced to internally balanced

So knowing that plus we are in another country we should balance the crank by it self? Works if you balance every piece separately? (Crank, damper, flywheel)

Your first, and last, posts are referring to very different things.

IIRC, some damp(en)ers are designed to be used for the fine balancing, the manufacturer(s) will send you the hub assembly, which you balance to suit the engine, then they will fit the outer ring assembly.

I would suggest checking out the web site FAQ for the company/ies you are interested in.

I think the subject here is a bit tricky - talking here to the local guy who is doing engine balancing he told me that he needs every rotating part attached to the crankshaft to do it properly, however at the same time fluidampr is not to be modified. When I asked him how critical is that for my particular engine he said ( surprisingly for me) that unless I'm planning to rev my 4cylinder inline engine above 8000 RPM it is not really critical and I can get away with stock balancing. Having said so he added that if it was v6 or v8 ( this is another project I'm working on) balancing would be absolutely a must to be done. I took his advice and did not balance my 4g64 engine at all with RPM limit of 7800.

Getting back to my previous comment. There are two basic ways of balancing an engine, internal where all the counterweighting is on the crankshaft, and external where not all the counterweight is part of the crankshaft but it is also done by using a front hub and flywheel which have part of the counterweighting built into them. What can cause confusion, and problems, is that with some engine series some will be internally balanced and externally balanced, and the correct front hub and flywheel MUST be used. This is where Cristian's confusion lies - the manufacturer is saying that one can't (or at least it is rather inadvisable) to machine off the counterweighting of an external type to try and make an internal type.

Georg, the two types have different primary and secondary balance characteristics, which you can check for on-line, and they make the balancing a bit more complicated, whereas a flat plane, in-line type crankshaft has much more simple primary and secondary characteristics.

However, while it isn't so critical, I would disagree with your builder as the original final balancing of the crankshaft assembly would have been for the original connecting rods, pistons, etc. and when you fit your carefully balanced connecting rods, pistons, etc. you are actually taking it further out of balance as they won't have the variations that the crank was initially balanced for.

Well, he said it is nice to have thing on inline engines but as long as they aren't revving too high it is not as critical as it is for V engines.

Gord, I see that the subject of balancing is a little more complicated than it seems or at least it is not clear to me yet, in the course they indicated that it is advisable to balance the crankshaft with the harmonic balance and the flywheel, but they did not elaborate further, I think it would be good if they could do a webinar talking a little more about internal and external balancing according to different options, for example:

I have a project of 1000hp and rev to 9k assembling with 4G63 block 100mm billet lightweight, cp piston, carillo H beam rod, but we are using the ATI damper for more security, twin clutch exedy, so how would you balance this engine? what would you do? Considering you have the lightweight crank, the ATI damper and the exedy twin clutch?

I think you can balance the ATI type as per normal, I think it was the fluid type that has issues as the fluid moves within the assembly, but if I were you I'd give them a call to check - there seems to be nothing in their FAQ, either way.

Failing that, I would go with what the chap doing the balancing recommended - he will certainly have more experience than I.

I haven't worked on one of those engines, but Georg has built a LOT of them - certainly I would have no problem taking his recommendations over mine ;-)

Gord, it is not mine recommendation vs yours. I am not recommending to go my way with not balancing rotating assembly - not at all. I'm just sharing my experience with my project and leave it up to people to make the decision. As I said if the engine is planned to be revving high - which is Cristian going to do- it is definitely required to balance the engine so we are advising the same thing. I just made a point that sometimes it is not 100 percent necessary to do that for inline engines - mine is doing absolutely fine with 3 bar of boost and RPM limit of 7800. Again, it is up to people to choose the option they like, i'm not saying my way is the only right way. Is a matter fact that I'm building two 2.2 4g63 engines now for customers and they are not going to be balanced for two reasons - the owners do not want to spend additional cost since the power level is going to be 500hp at flywheel only - not a very big load for this engine. I know you are very experienced person and I never meant to undermine your opinion...

Sorry, Georg, didn't mean your word should be taken as gospel, but that because you've had a lot of experience with that particular engine, and I don't, that your words of wisdom should carry more weight. Doesn't mean we're in competition, or that we can't BOTH be wrong ;-)

Personally, I feel that some people put too much weight on getting everything perfectly balanced - there is at least one 'tuner' that makes a point of telling people that he balances to 0.1 gram - and I recall many years ago a record being set on an engine the driver said had 3 different brands of pistons and 2 diferent brands of connecting rods (might have been the other way round) because that's all they had left after a series of breakages and other problems. It takes a lot of vibration out of the engine, and it runs smoother, but there's a point where close enough is good enough - opinions may differ, though, and I'm not a professional paid to build engines.

Hi Guys,

So maybe Andre could clarify doubts, personally I am not very clear.

Here I attach the information that comes with the ATI Damper for a 4g63, that may help.

Attached Files

Those tell you everything you need to know, and are asking about. Outer ring isn't used for balancing, but the hub that is attached to the engine is - send the hub in with the crank, flywheel, pistons, 'rods, and as much of the clutch assembly as the balancer requests.

Yes it is correct, with the ATI it says that only with the hub can the crankshaft be balanced, but I still have a problem with the multi-disc clutch, since the flywheel is different and to do it assembled would have loose parts which does not allow obtaining a constant balance.

Another other question I asked at the beginning was, to make the balancing the balance shop needs the 3 pieces assembled together (Crank, Damper and flywhell) to achieve the balancing they take weight off the counterweight of the crank is what I understand, so when You have a lightweight billet with very fine blade counterweights it is impossible to take off weight, so how could it be done in that case? someone has passed for that?

So you have a crankshaft without counterweights that can't be balanced. Because if you did have counterweights, then by definition weight could be removed.