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.

 

[Civib2]

thanks a lot terry for all your help I will post some pics as soon as the car is done and dynoed hoping for 300whp at 18psi with the portfueler

 

[insanewayne]

Ok, I know it has been beaten to death, but after reading for an hour I still don't have a straight answer in my head.

I am rebuilding my motor, .020 over ross 8.5:1, eagle H-beams, removing balance shafts, fidanza and ACT 2600. I've read that the stock crank is balanced already, and the high quality Aftermarket rods and pistons are so close to eachother in wieght that it doesnt need to be done. However my flywheel/clutch assemly might be worth balancing.

Then I have read in the same threads that the Rods/Pistons need to be balanced TO the Crank?

This motor will be revving to 8500-9K.

So far I have:

Hot tank block
Bore and hone .020 over
Crank polish
Deck block for MLS
Balance rotating assy ???!
Do I need to line hone the Mains if I'm going to use ARP's?


Will be running stock head with 272's and some upgraded springs, SCM-6169E, and supporting mods.

Thanks for your time,

Wayne

 

[Enraged78]

Do yourself a favor and have the whole rotating assembly zero-balanced. This includes the pistons, rods, wrist pins, crank, flywheel, and harmonic balancer. When the balance is performed, the pistons and rods will be match-weighed and have possibly have material removed to get the weights as close as possible. Close is under a gram. The machinist will then balance your crank, harmonic balancer, and flywheel as a unit. Good machinists can balance this to a gram or lower. A proper balance will also help your engine longevity, especially if you plan at running higher than stock RPMs.

I have no balance shafts and a zero balanced Ross/Eagle 7 bolt with poly engine mounts. The only vibrations the engine demonstrates are at idle, and that's mostly due to the mounts. The engine is silky smooth in any other RPM range, and a pleasure to drive as a result. I've been in cars without balance shafts that have not been balanced, and it's not as nice. I've had people in my car who know DSMs very well comment on how amazingly smooth the engine is. When I tell them I have no balance shafts I always get the same 'holy shit' expression.

I did not line bore my mains, but I have a 7-bolt, and they do have girdles. It spec'd out well within tolerances, so we left it alone. Line boring a 6-bolt is really your preferance.

P.S. Get your head decked as well by a reputable shop if you plan on running an MLS gasket.

Matt.

 

[TSIfreek]

V8s and v6s get there rods and piston weights added to the crank and then balanced. From what I know 4 cylinder cranks get balanced without the rod and piston bob weights added to them. I think this is done because the 4 cylinder motor is straight up and down not at angels lilke the V8s and V6s I may be wrong but I have never seen a 4 cylinder crank with bod weights on it.
The piston weights are real close if going with a piston like a ross or weisco but have them double checked as well as the rods but they should be close as well. The weights may be writen on the box.
I would get the crank balanced if any work is being done to it if not have it rebalanced anyway. I do as much work as I can while I have the motor out because of all the time and money being put in to it I dont leave anything to chance.
Also do yourself a favor and get a new oem harmonic balancer or a fludine.

 

[steel_3d]

I would align hone the mains with ARP's, since the different torque settings will distort the caps differently than stock bolts. Normally I would leave the stock bolts at stock torque and not worry about honing, but at 9k it might be worth using the arp's, since you're gonna have larger forces exerted on your mains.

The reason I went with arp's is because my stock bolts were stretching every time I torqued them. Felt like they've yielded.

I'm also balancing everything, cause I might as well. My Wisecos are off by more than 1g, I'd rather have them closer. Who knows about everything else.

Can someone explain more about balancing a 4-cyl? I was talking to this shop and he kept talking about bob weights, adding lead shot, and slightly overbalancing for high-rpm use. He's a domestic guy, but I would hope he would know the most basic things about a 4-cylinder... I'm also using a stroker crank, not sure how that affects the balance.

 

[Suparata]

...I was talking to this shop and he kept talking about bob weights, adding lead shot, and slightly overbalancing for high-rpm use. He's a domestic guy, but I would hope he would know the most basic things about a 4-cylinder...

You may have to look somewhere else if your machinist is talking about bob-weights and heavy metal to balance an in-line engine. TSIfreek was pretty much on the money with the above post.

 

[TSIfreek]

I was hopeing mitch was going to comment on this one he is the 4g63 master.

 

[insanewayne]

Isn't my current harmonic balancer mated to my engine? For example mine has like 6 holes drilled in for balancing, while my friends has one. Or is that the hole idea, you buy a new undrilled one, and the machinist balances it into the assembly? Is there even a point if mines fine?

I'm going stock springs, titanium retianers for the head, with my 272's.

ARP mains, line hones, which holy #### me is expensive
And, because I can't locate a torque plate on the stupid Island my machinist and I are splitting the cost on making one and he'll just keep it afterwards for future builds. So I will be boring/honing .020 over with the torque plate and main torque with moly lube etc....I don't think I'll go as far as to run hot water through the block while doing it though, but hey we'll see.

Another question I have, is simple, just need some experiences or true facts here. I know that eagles are proven for are application, but I have heard stuff about either ends not being the right size and extra machining needed etc. Wether or not it's just web forum bullshit, I don't know. But from what my lordco guy tells me, scat is a better rod, and similar in price. Just cause a brand isn't used a ton yet for our engines, doesn't mean it can't be better.

Anyways, if anyone KNOWS anything about scat rods, the info is appreciated.

Thanks,

Wayne

 

[Suparata]

Inline engine balancing is done by individually balance each component that gets bolted to the crank and the crank itself. Rods and pistons are weight matched to the lightest one and just because aftermarket rods weigh overall is pretty close it doesn’t mean that their small and big ends weigh the same.
Your damper is balanced (sort of) from the factory and there are not too many places that can get it better so you will have to live with it.
In the last 4 years I have not seen an Eagle rod for a 4G63 that measured right so I’m not sorry I stopped using them. Especially when there is a better alternative out there: Scat. These are stronger but most of all they are DEAD ON-SIZE every time. And that goes for any other application in which we used Scat.

 

[steel_3d]

For what it's worth, my Eagles measure out fine. We'll see if they're straight too when they get to the shop

 

[insanewayne]

Thanks Mitch.

So would you suggest I get a new Hanmonic Dampener, and have it balanced with the rest of the assembly? Or will my current stock one be fine if it's in good shape.

 

[aleccolin]

First, I'll give you the whole plan for the bottom end I'm about to build. Pretty standard, really.

6 bolt 4G63 block
G4CS crank, .25mm cut on rods and mains, appropriately sized bearings
Ross forged 9.0:1 stroker pistons, .5mm oversize, with Ross racing rings and wristpins
Eagle H-beam rods, come with ARP rod bolts
Deletion of balance shafts using Mitsu parts
Fresh front cover/oil pump from Topline
Fluidampr harmonic damper pulley

My question pertains to dynamic balancing of the rotating assembly. How critical is it really? I know the pistons and rods are heavier than stock, so I'm thinking I had better have it done. The Fluidampr is going on just as an added measure of safety against any harmful harmonics that might occur, not an attempt to make up for removing the balance shafts.

 

[jpbrazill]

My question pertains to dynamic balancing of the rotating assembly. How critical is it really? I know the pistons and rods are heavier than stock, so I'm thinking I had better have it done. The Fluidampr is going on just as an added measure of safety against any harmful harmonics that might occur, not an attempt to make up for removing the balance shafts.[/QUOTE]

How are your rods and pistons heavier than stock 2.0L cast stuff?

When i built my 2.4, i did not get anything balanced. It runs fine, however, Im never going to wrap my motor to 9,000 or anything either.

You might want to balance everything you have now. I dont regret not balancing my motor, but I wish I had.

J.P.

 

[aleccolin]

My question pertains to dynamic balancing of the rotating assembly. How critical is it really? I know the pistons and rods are heavier than stock, so I'm thinking I had better have it done. The Fluidampr is going on just as an added measure of safety against any harmful harmonics that might occur, not an attempt to make up for removing the balance shafts.

How are your rods and pistons heavier than stock 2.0L cast stuff?

When i built my 2.4, i did not get anything balanced. It runs fine, however, Im never going to wrap my motor to 9,000 or anything either.

You might want to balance everything you have now. I dont regret not balancing my motor, but I wish I had.

J.P.[/QUOTE]

Eagle 6 bolt rods are 575 grams. The Ross 6 bolt 9:1 stroker forged pistons are 345 grams, plus heavier (stronger) pins. The stock pieces, though I haven't found any actual weights, have got to be lighter than those, especially since forged pistons are almost always heavier than cast hypereutectic.

If I can just bolt it all together without having to have it dynamically balanced, then I'll do it. I'll set the rev limit at 7500 and I'm building this motor for low end grunt, but I MAY end up doing a few track days with it, so I want something that can hang out at 7k all day without a problem. Just getting opinions on whether or not it's worth the extra expense to have it balanced.

 

[Enraged78]

Eagle 6 bolt rods are 575 grams. The Ross 6 bolt 9:1 stroker forged pistons are 345 grams, plus heavier (stronger) pins. The stock pieces, though I haven't found any actual weights, have got to be lighter than those, especially since forged pistons are almost always heavier than cast hypereutectic.

If I can just bolt it all together without having to have it dynamically balanced, then I'll do it. I'll set the rev limit at 7500 and I'm building this motor for low end grunt, but I MAY end up doing a few track days with it, so I want something that can hang out at 7k all day without a problem. Just getting opinions on whether or not it's worth the extra expense to have it balanced.

I had my stock displacement 7-bolt zero balanced. This included the crank, balancer, and flywheel. Pistons, rods and wrist pins were all weight matched to .01 grams. The end result is that vibration only occurs at idle with poly mounts. The engine is smoother than it was stock with the balance shafts at any other RPM level, including 3500RPM, where used to get some resonance.

Balancing a rotating assembly isn't just to keep the assembly from shaking it self to death at 8K. It also helps tremendously in making the motor more enjoyable on the street. It's nice to be in a hard turn at 6K and not worry about the vibrations from your steering wheel throwing you into a ditch.

Matt.

 

[aleccolin]

Thanks for the info man! I was under the impression that the rods/piston assembly was weighed and that weight was used to balance the crank. I guess there's different ways to do it, I didn't think the flywheel and all was that important to include, but I guess maybe. I would really love to have a nice, smooth engine as this is a street car.

 

[AL92]

I just built a 2.4 and didn't balance anything. I don't believe in this balancing it with the clutch and flywheel crap..what if you change clutches and flywheels? And heard stock cranks are pretty closely balanced anyway as are most aftermarket pistons and rods.I have crower rods and wiseco pistons. I did buy the new fluidampr as the stock balancers separate at random miles. I had a few do that already on me.! JUNK!!
I have built many other motors in the past and never bothered to balance them either.
I really think its a bit of an engine shop con personally but hey its your money.

 

[aleccolin]

I just built a 2.4 and didn't balance anything. I don't believe in this balancing it with the clutch and flywheel crap..what if you change clutches and flywheels? And heard stock cranks are pretty closely balanced anyway as are most aftermarket pistons and rods.I have crower rods and wiseco pistons. I did buy the new fluidampr as the stock balancers separate at random miles. I had a few do that already on me.! JUNK!!
I have built many other motors in the past and never bothered to balance them either.
I really think its a bit of an engine shop con personally but hey its your money.

No, that's fine, thanks for the input. The more I look into it, the more I'm thinking it won't be necessary. The crank should be balanced well enough, and it's a planar style crank (all journal centers lie in the same plane) so I should be able to rig up something to check the static balance. The 1-4 and 2-3 journals are 180 out of phase with each other, not like a V engine, so as long as the pistons and rods are manufactured within pretty close tolerances (which they are), the assembled weights should be very close, and shouldn't cause any unwanted harmonics. Just to be sure I'll borrow a digital lab scale and match up piston, rod, and pin pairs to get the closest possible weights across the board. The flywheel shouldn't matter as, if I remember, it's not weighted, and the fluidampr should help with any minor harmonics that might appear under operation.

The expense of sending off the rotating assembly to be balanced just doesn't justify the minimal gains in this case, especially since I don't intend to flog it at high revs on a regular basis like I might a race engine. If anyone has anything else to add, please do, but for now I'm going to plan on not going through the trouble to have it balanced.

 

[GVR4592]

My cousin just weighed his eagle rods and ross pistons. They varied almost 2 grams from cylinder to cylinder. That's a lot. It should cost under $150 to balance the engine, I would just do it.

 

[Enraged78]

I just built a 2.4 and didn't balance anything. I don't believe in this balancing it with the clutch and flywheel crap..what if you change clutches and flywheels? And heard stock cranks are pretty closely balanced anyway as are most aftermarket pistons and rods.I have crower rods and wiseco pistons. I did buy the new fluidampr as the stock balancers separate at random miles. I had a few do that already on me.! JUNK!!
I have built many other motors in the past and never bothered to balance them either.
I really think its a bit of an engine shop con personally but hey its your money.

My crank was out 20 grams from the factory when we balanced it. Your flywheel and harmonic balancer do play an important role in balancing the rotating assembly. Your mileage may vary. If you zero balance your crank, harmonic, and flywheel seperately, it should make no difference than if you balanced it as a unit. The only difference is that it should be less work for your machinist to balance it as a unit.

Matt.

 

[Enraged78]

My cousin just weighed his eagle rods and ross pistons. They varied almost 2 grams from cylinder to cylinder. That's a lot. It should cost under $150 to balance the engine, I would just do it.

I had the same setup on my build, and the exact same problem. Two of my pistons were 4 grams apart! We match weighted the pistons and rods to get them as close as possible, then removed material from the heaviest pistons to get them to match the lightest ones. We also fly cut the skirts to help prevent piston slap. In the end, each piston and rod combo weighed the same with a variance of .01 grams between all four. Luckily, my Eagle rods were in round, which not all are.

Matt.

 

[Enraged78]

No, that's fine, thanks for the input. The more I look into it, the more I'm thinking it won't be necessary. The crank should be balanced well enough, and it's a planar style crank (all journal centers lie in the same plane) so I should be able to rig up something to check the static balance. The 1-4 and 2-3 journals are 180 out of phase with each other, not like a V engine, so as long as the pistons and rods are manufactured within pretty close tolerances (which they are), the assembled weights should be very close, and shouldn't cause any unwanted harmonics. Just to be sure I'll borrow a digital lab scale and match up piston, rod, and pin pairs to get the closest possible weights across the board. The flywheel shouldn't matter as, if I remember, it's not weighted, and the fluidampr should help with any minor harmonics that might appear under operation.

The expense of sending off the rotating assembly to be balanced just doesn't justify the minimal gains in this case, especially since I don't intend to flog it at high revs on a regular basis like I might a race engine. If anyone has anything else to add, please do, but for now I'm going to plan on not going through the trouble to have it balanced.

Balancing the pistons and rods in a V8 and and Inline 4 are completely different (...the difference between a flat crank and cross-plane; there are exceptions to this, like flat crank V8's found in the V8 SHO's and Ferrari engines, etc.). On a V8, you balance the pistons by supporting the crank end of the rod in a jig and weighing the piston end. It looks something like this:

( )===|||
^Jig
Scale ^

Inline four pistons and rods are balanced by getting the weights as close as possible.

Matt.

 

[Turbocharged]

I had my 2.4 balanced. I was worried about vibration with no balance shafts. The pistons/rods were weight matched and the crankshaft, flywheel, clutch and pressure plate were balanced together. The builder told me the most unbalance of the components was the pressure plate. So now I have the problem of having an unbalanced motor when I go through this clutch and have to install a new pressure plate. For the time being I have no noticeable vibration except at through the steering wheel at idle (motor mount inserts and a 2.4...).

If I could do it again I would have everything balanced, minus the pressure plate and clutch (for the simple fact that they get replaced often in these types of setups).

 

[AL92]

Well guess find out how bad not balancing anything in my setup is going to cost in terms of vibration shortly. I did have energy rollstop inserts to install also. Not 100% sure I should use them in an awd? I think more important in a fwd.

I am hoping my new fluidampr helps out in the vibration department. And as said you change out flywheels and clutches so balancing with them dont' make that much sense to me. You change them out you aren't going to yank the motor out of the car to balance stuff.

Each to his own I guess. If I have horrible vibrations you guys can say you told me so!!!

 

[Turbocharged]

I did have energy rollstop inserts to install also. Not 100% sure I should use them in an awd? I think more important in a fwd.

I didnt think I needed inserts or different motor mounts either. After my first WOT run I snapped the rear motor mount. About 500 miles later the front mount went. You'll be suprised what extra torque does in terms of twisting the motor around. I went with front and rear inserts and havent had a problem since.