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How to balance your valve train


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Did you balence the camshaft also? THat would have a major effect on balence, as the cams are far from perfect, I would balence the cam.

 

Did not balance cam. I am sure there has to be some advantage to balancig it. Just never heard of anyone doing it before. Not even sure if it is possible

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Did not balance cam. I am sure there has to be some advantage to balancig it. Just never heard of anyone doing it before. Not even sure if it is possible

 

LOTS of top end guys do it, cams are never right, out of the box, just like anything else. MUCH more important IMHO than balencing rocker arms, When I balencend mine before, they are pretty far off. At 8k rpm, it can be really bad, just like a crank. Many people over look the situation.

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  • 11 months later...
Guest Widebodys30
One of the things to keep in mind about this entire procedure is that it is not creating any power it is only assisting longevity of the parts. As stated in the other thread the time could be used better in other places (as far as creating additional power).

 

In a nut shell by doing this balancing work you are creating a more fluid interaction of parts which in general will cause the parts to last longer and handle greater extremes but will not create any power that is not already there.

 

I disagree, for 2 reasons. Gotta give credit where due, Boss.

AWESOME work. You are too humble.

 

1) You are removing material from the reciprocating assembly, making it lighter, less power to operate, more to wheels.

2) The balancing itself will help the engine make power, as in theory, each cylinder will be operating much closer to the parameters of its brothers. If each cylinder is equal in output, the whole motor makes more power.

 

 

I would be willing to bet a large sum there's a measurable gain.

 

Would love to see a very controlled dyno pull, with EVERYTHING the same, including same head, ambient temp, humidity, ect., but the balanced valvetrain...

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1) You are removing material from the reciprocating assembly, making it lighter, less power to operate, more to wheels.

 

Uhm, no. Removing material is involved, yes, but only to the extent of matching the numbered piece lightest in weight of the set. Balancing implies no particular "removal of material" in a sense that is weighed other than for comparative purposes. The actual mass shed is utterly minimal in terms of reciprocating assembly.. It is so relatively minimal, in fact, that the effects that ARE felt from that tiny mass reduction are felt more in terms of camshaft drivetrain wear than in specific power output. In other words, that 0.5 grams total mass (or whatever, its been a LONG time since I read this thread through) will have more of an effect on making your timing chain last longer than it will have in giving you "that little bit less mass to spin around."

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Uhm, no. Removing material is involved, yes, but only to the extent of matching the numbered piece lightest in weight of the set. Balancing implies no particular "removal of material" in a sense that is weighed other than for comparative purposes. The actual mass shed is utterly minimal in terms of reciprocating assembly.. It is so relatively minimal, in fact, that the effects that ARE felt from that tiny mass reduction are felt more in terms of camshaft drivetrain wear than in specific power output. In other words, that 0.5 grams total mass (or whatever, its been a LONG time since I read this thread through) will have more of an effect on making your timing chain last longer than it will have in giving you "that little bit less mass to spin around."

 

Agreed - I don't think that you'll see a measurable increase in power from this if everything else is left the same.

 

Where you might see an increase from the decreased mass could come from a decreased tendency to float the valves, allowing selection of a higher revving cam (needs lots of supporting mods), or you might be able to run lower tension valve springs and keep your current redline and get a power increase from friction reduction.

 

As I recall I was able to reduce the levered mass by something like 3 grams, so the effect is not insignificant, but you'd probably still want to combine this with other valvetrain lightening efforts (titanium retainers, lighter valves, etc) in order to see a measurable power increase.

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  • 10 months later...

Well to be really anal about it, that scale has an error uncertainty of +/- 0.1g, so every time you used it, there is that uncertainty to take into consideration with you calculations! I dont have the time nor inclination (or data) to do a proper uncertainty calculation, its most likely that your balanced to 0.25g would also have a +/-0.5g of uncertainty to it!

*Also you cant be using a decimal measurement lower than you highest uncertainty, as you scale is only a 0.1g, then you cant be using a value less than one decimal place in any calculations!

 

Sorry to be so anal about it, but i felt it needed to be made aware of!

 

I have access to 0.0001g scales in the lab, which are in pressure constant rooms, even my breathing with the lid open will move the reading by +-0.0005g!

I quite often have to be accurate to 0.001g or better, which is really quite fiddly sometimes (and the uncertainty calcs are quite annoying)!

 

 

Im glad you took the levered mass of the rocker arms into account (was that done at the correct lash setting though?)!

As for the springs, i cant see any real reason to weigh them, it would be far more important to measure the tension & rate of return! Balance that instead!

I cant see a purpose for balancing the cam either! Its a not a Dohc so nothing to match it to! Its a rotating mass working as one unit, so i wouldnt matter if one end is slightly heavier than the other in this case (its not the same as a crank), but it cant hurt if your keen enough; unless you mean dynamic balance, then yes!

Also the tension of the mouse traps should be measured & balanced too!

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Im glad you took the levered mass of the rocker arms into account (was that done at the correct lash setting though?)!

As for the springs, i cant see any real reason to weigh them, it would be far more important to measure the tension & rate of return! Balance that instead!

I cant see a purpose for balancing the cam either! Its a not a Dohc so nothing to match it to! Its a rotating mass working as one unit, so i wouldnt matter if one end is slightly heavier than the other in this case (its not the same as a crank), but it cant hurt if your keen enough; unless you mean dynamic balance, then yes!

Also the tension of the mouse traps should be measured & balanced too!

 

My take on this is that if you are going to go to the trouble (and it is a LOT of trouble!) to "balance" the rocker's to within a gnat's behind, then you must take the unsprung weights of all of the moving parts in the assembly into account (i.e. the rocker and everything that moves with it - retainers, lash pads, springs, valves), or the exercise make no sense whatsoever. This would be akin to spending $4000 per corner on the lightest suspension parts available, and then using 50lb steel wheels, each from a different car.

 

After re-reading your post, where you mention balaning the rate of return, you would have to take these additional weights into account in order to achieve this.

 

Really this has much more to do with reducing valve float uniformly across all cylinders than anything else. The only effect that this can have on the reciprocating balance of the engine is from the decreased force required by the cam to overcome the rocker's inertia and move the rocker up and down. Since we are only changing things by a few grams here, this effect is hugely drowned out by the friction presented by the valve springs pressing the rocker against the cam lobe.

 

If you are only going to spin to 6000rpm anyway, then you probably won't see any benefit from doing this, but if you want to regularly go higher in the RPM range, then it starts becoming more and more important.

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ahaha Tony, yeah i love my exclamtions! (i dont know, why but its something i only do in forums.)

 

 

 

Tim, i think you may have missed what i was getting at? Yes, weigh the collets, retainers, lash pads, valves etc. But the spring itself, is not nessesary (do you weigh the spring washers?), but the tension & return rate, are the factors involved in the balance. The weight of the springs is of no consiquence, if the prior factors are taken into account.

The levered rocker arm weights should be balanced at their correct lash settings (ie: respective angle in relation to the lash pad {height of pivot}), so as to get a true indication of what weigh percentage is actually placed on the lash pad.

I understand the dynamics very well and yes i intend to run my stroker to well over 8k! I intend to use some very exotic parts to assist that, when i eventually build it.

My L18 pulled over 8k regularly, using mostly factory parts in the valve train (springs excluded).

 

oh, the $4g suspension & 50lbs wheels: well a 50lb wheel, is a 50lb wheel! lol Maybe fine suspension modulation was important, but you wanted to maintain a high rotational inertia, then that would be good..... possibly dakar?

 

Anyway, so yes, i mostly agree with you, but i was just being really anal about it. lol (as someone said earlier, "if your going to be anal, might as well be really anal!".)

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Wow, very impressive! :shock: Thats moving alright!

 

14.75:1 CR YIKES!!!!!!!!!!!!!!!!! (and a few more just for Tony)!!!!!!!!!!!!!!!!! :icon45:

 

 

 

*Just to note: i was in no way attempting to devalue the work that was done in balancing, its very good work. I admire his patience and fortitude in doing so! There is definately something to be gained for all of us from his work. But i was just highlighting some details that needed clarification, by bringing abit of science to the table. Sorry, i am doing analytical chemistry at the moment, affectionatly dubed "anal" chem! lol

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If you could see the valvetrain on the subject of that You Tube Post...

 

Well, let's just say, it's not what most people expect. The prep work in this sticky is far more than what we did on that one...

 

And we have had it 'higher' than the shift point during dyno testing to see the extent of the curve and try to find a 'float point' on the valves.

 

We were...uh....'unsuccessful' in that float-point attempt. That's all I'm gonna say about it.

 

It tempers my comments about nits and nats on this subject!

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*Just to note: i was in no way attempting to devalue the work that was done in balancing, its very good work. I admire his patience and fortitude in doing so! There is definately something to be gained for all of us from his work. But i was just highlighting some details that needed clarification, by bringing abit of science to the table. Sorry, i am doing analytical chemistry at the moment, affectionatly dubed "anal" chem! lol

 

oy...

 

But then again, tony highlighted your * nature and then included a parenthesized exclamation point, which is an old keyboard rendering of an arse....

 

*(I couldn't actually say anal there and infer it as your nature. Seemed too forward. Woops.)

 

But seriously, we like people who spell things out here when they speak accurately. (Or was that precisely? hmmmm....)

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