Engine balancing [Merged 6-7]

[Stock90GSXT]

Okay. I need some advice. I removed the balance shafts out of my 6bolt. I have heard two different sides.

1. The engine is'nt balance w/o those, so get the Rods, Pistons, and Crank,flywheel balanced

2. The engine is already balance w/o the balance shafts, they were just there to remove vibration so customers would'nt complain.

I was thinking. If the engine was vibrating. then its not balanced. I need imput from the people who have had experiance in removing the balance shafts. Is it worth it to balance the bottom end. Or is it a waste of money?. Keep in mind. I will be changing the perimeters by installing 95+ pistons on my 1g Rods. I know anytime you change stuff like that its recommended to balance the engine.

 

[MNGSX]

Also BUILD A 6 bolt.

Knife edging cuts crank rotating weight down (good) and windage (~churning oil) also good.

blue-printed or blue printing just means the machinst did his homework and machine work right.

All bores straight and honed with a deck plate to the piston MFGs wall clearance as measured by the piston MFG's specific proceedure on where on the piston to measure the clearance from. Decking the block and head just a little to get them straight and at the right surface finish. Things like that.

The main question was balancing. Its so easy on a 4 banger nobody should pay much if anything for it.

 

[7boltnewbie]

Ok thanks for the insight guys.

 

[Mike1992]

How much is to much? $$$ wise I just dropped my crank, 1g big rods, 2g pistons and ARP rod bolts off to have everything done up. I asked how much balancing was and he said $135 is that to much? He said machining my rods was gonna be pretty costly to

 

[zrk666]

Unless its a cracked and or mis resurfaced old beat up flywheel or a autochrome pulley w/o a harmonic damper nothing that bolts to the crank outside the block matters on a 4g63 because its all neutral balance.


i have one question?

is a crank pulley with a harmonic damper needed with a balanced engine?

 

[MNGSX]

Yes...

 

[turbotsi92]

I would not balance the engine for a street car, you are going to see none to very little performance from it and pay the 135.00 extra dollars. If you were building a track car that is one of the little tweaks to give you a little bit. Listen to the first reponse you received. I am in agreement with that.

 

[MNGSX]

Not to mention that the best street forged pistons wiseco are so close in weight tolerances some engine shops dont balance that good using other MFG's..

Wisecos + Eagles or other rod of your choice = balanced enough and almost a race balance depending on factory crank tolerences.

Compared to a V8 crank there is hardly any weight on a crank....

A racing engine would get a BR or FFWD butcher or my buddy down the blocks work... oops... gave a away my crank...

The next engine I build I will shoot and type a DIY engine balance article...

 

[99gst_racer]

Whether it be .5 grams or 1 gram, how exactly do you remove weight?

 

[Mike1992]

grind away

 

[MNGSX]

Yep but do it somplace where you dont need the material..

Honestly with wisecos since they are so close you could use a large diameter chamfer drill bit and drill the inner end of the wrist pin on each end.. Take off enough that when this pin goes in the heavier of the pistons it matches the others..

In the above example piston weights were...

336.4, 336.4, 336.4, and 336.0... We need to take .4 grams off of 3 of the wrist pins....

Assuming all the wrist pins match.. They vary too. which is why I just weighed them seperate and matched them up with a piston based on how close it made each piston pin package. In that case matching the 3 of the wrist pins and leaving one .4 heavier would be the best course of action..

Honestly with .4 grams variance on the pistons and about the same on the rods there is'nt a lot to take off anywhere..


http://www.diynetwork.com/diy/ar_replica_car_kits/article/0,2021,DIY_13707_2272192,00.html

They weighed the piston pin and ring package at once.. I weighed every single part seperate and kept track of which one weighed what. Then I picked the piston and pin combinations that made the assembly weights the closest... Ring package weight variations were not measurable.


On part 2 of that link ignore the stuff about bob weights and dynamic balancing of a v8.... That is V8 only.....

The way you check rods on the scale is the same and a crank can be dynamically balanced by itself but does not use bob weights clamped to the journals like on a V8.

 

[blackGSX2g]

Whether it be .5 grams or 1 gram, how exactly do you remove weight?

For the con-rods, there are usually kind of a baffle-like material on the edges. If you look at your stock rods, you will see this as well and sometimes you can see where they don't look exactly the same, this is where you can grind them.

For pistons, as stated before, sometimes all you need to do is match the right wrist pin with the piston and the weights should be fairly close (+/-) .1g. Also have to take in consideration your piston ring gap. As you remove material from there (if you need to) it also changes the weight, though if your gap is fine don't use that as a method of balance.

I didn't feel comfortable removing weight from the wrist pin, so I would go with a drill bit to the piston. I've got Weiseco pistons as well and found that most of the time, all you need to do is match the wrist pin to the piston and they should be close enough.

I balanced my own using a simple gram scale and a grinder and a bit of time. Cost me a total of $0.

 

[MNGSX]

I didn't feel comfortable removing weight from the wrist pin, so I would go with a drill bit to the piston. I've got Weiseco pistons as well and found that most of the time, all you need to do is match the wrist pin to the piston and they should be close enough.

After you match the pins to put the assemblies close the diffence is in the low tenths of a gram... . .10 to .20 total per pin equates to .05 to .10 grams off each end of a wrist pins inner bore is nothing. Its not aluminum so its heavier and even less volume of material has to be removed. They look factory if done right...

You also have the option of taking the weight off the small end of the con rod instead if you wish... Just polish it after and grind in the right direction....

less than .5 grams of rotating weight difference is nothing... Big end of rod... so I dont bother with aftermarket rods that spec in really tight on the scale ...

You could probably have a really long living race engine just by assembling wisecos and even eagle rods as is... The bore finish, bore tolerances like round straight square to deck, and the piston to wall clearances are 100x more important...

A dead on balance is a short put in comparison starting with the right parts.

 

[zachdeagle16]

When I built my engine, I had my rotating assembly balanced. My question is, when I get a new clutch, will I need to have it balanced like the old one was?

 

[ereckerdeet]

No, what they did when it was balanced was make sure the crank's rotation is balanced, and that the pistons/rods are balanced as a set. The new flywheel/clutch/pressure plate will come balanced from the manufacturer.

 

[Civib2]

Hey guys, i just sent my block to the machine shop to get bored 20 over and homed. My question is to you guys who have done this already. Did you balance your entire motor? or did u guys just throw in the new pistons as is. My crank is getting knife edged and balanced as well as polished. So now what i am figuring out is that i have to take the new pistons and rods over to the shop and have them weigh them to see if they weigh as much as the stock ones do. has anybody done this?

 

[turbohcar]

The idea behind balancing is not to make sure that they all weigh the same as the stockers. The idea is to make sure that each of the new rods weigh as much as the other three indifidually. Same with the pistons. Think of the piston/rod/crankshaft assembly as a bicycle wheel. If you stick a 5lb magnet to one end of the bicycle wheel and nothing to the opposite side, it's not going to spin properly. When you balance the rotating assembly you're making the rotation smoother, which can make more power.

I'm not sure if I'm explaining this to it's fullest extent so somebody else can feel free to jump in on this for me. Thanks

 

[selmerguy]

The idea behind balancing is not to make sure that they all weigh the same as the stockers. The idea is to make sure that each of the new rods weigh as much as the other three indifidually. Same with the pistons. Think of the piston/rod/crankshaft assembly as a bicycle wheel. If you stick a 5lb magnet to one end of the bicycle wheel and nothing to the opposite side, it's not going to spin properly. When you balance the rotating assembly you're making the rotation smoother, which can make more power.

I'm not sure if I'm explaining this to it's fullest extent so somebody else can feel free to jump in on this for me. Thanks

Almost.. The ideal of balancing is to make sure all the rods weigh the same as well as the pistons. The crank is supposed to be balanced from the factory. If you bought good internals like eagle rods and je pistons the are all perfect. Mine were down to the miligram. So it should stay balanced. Some people go way out and put on the pulleys and flywheel. IMO this does very little. Some swear by it though. I didnt balance or "shake" mine and it is still fine after about 5,000 miles and some hard driving. I know of more people that didn't balance there crank after a rebuild and run strong and very well. I also have not heard anybody having balance problems after a rebuild with good internals and not balancing. If you have the money and want the piece of mind do it. But I dont think it helps much.

 

[Talon ESI-T]

Not quite guys.

When you balence a rotating assy, the pistons and rods are balenced to be equal but the weight of each rod/piston combo is balenced against the respective counter weights of the crank.

Everytime you change a rod or piston, you need to check balencing, especially if you are changing piston sizes ect.

Balencing is for protection of bearings and integrety of the lower half. For overall motor vibration, balence shafts are used in some motors like the 4g series and the Chry 2.4.

Terry

 

[selmerguy]

Not quite guys.

When you balence a rotating assy, the pistons and rods are balenced to be equal but the weight of each rod/piston combo is balenced against the respective counter weights of the crank.

Everytime you change a rod or piston, you need to check balencing, especially if you are changing piston sizes ect.

Balencing is for protection of bearings and integrety of the lower half. For overall motor vibration, balence shafts are used in some motors like the 4g series and the Chry 2.4.

Terry

They balance the the rod and piston against the big lob counter weights on the crank? Thats good to know. Guess I am going to take apart my motor now

 

[Civib2]

Thanks guys, any more input?

So my question is do I need to balance it, because its all at the machine shop right now and when i get it back i want to start building. Do you guys think I will be safe doing what i am doing? Also what exaclty does knife edging a crank mean? But my crank is getting knife edged and balanced and polished the block is getting homed bored 20 over and decked so with this all happening will I be okay in my garage building this thing when all parts are here without balancing the entire assembly? What can happen from not balancing it?

 

[selmerguy]

Thanks guys, any more input?

So my question is do I need to balance it, because its all at the machine shop right now and when i get it back i want to start building. Do you guys think I will be safe doing what i am doing? Also what exaclty does knife edging a crank mean? But my crank is getting knife edged and balanced and polished the block is getting homed bored 20 over and decked so with this all happening will I be okay in my garage building this thing when all parts are here without balancing the entire assembly? What can happen from not balancing it?

I think you will be fine. Bad balance would leak to bearings going bad faster and maybe leaking around your crank seals.

 

[Talon ESI-T]

You want to have the shop balence the rotating assy, this is a must for a smooth, strong, performance motor. There is nothing wrong with assebling the motor in your garage as long as you have the proper tools and know what you are doing. You should be measuring and checking clearances as you build it. Dont forget to check the clearances of the crank and rod bearings as well. Very important and should not be left out.

Knife-edging the crank: The machine shop will take the leading edge of the counter-weights and machine them to a point. Kinda like the edge of a knife. This allows the crank to spin through the oil cloud that is spinning in the crank case. The factory crank is knife-edged already.


From not balencing the rotating assy, the motor will develope uneven wer patterns and will need to be rebuilt much much sooner. It is not surprising to develop bearing problems as soon as 10k miles. The motor can also have a great deal of vibration as well.

Terry

 

[Civib2]

yeah, I guess im just going to have them balance the entire assembly. So what do I have to give them, my pistons, rods, and rings and thats it so they can weigh it all? And how much do you guys think this is going to cost im going to go find out tomorrow, im already up to 400$

 

[Civib2]

okay so im getting it all balanced for 275$. now what to do about the head gasket? Do i need to find a custom head gasket because im boring it out 20 over? or can i just stick witht he stock MLS gasket and it will be okay?

 

[Talon ESI-T]

Stock MLS gasket is the best choice. Proven to take a beating.

Terry