balance rotating assembly

[Drifter27_04]

How critical is it to have the rotating assembly balanced? Can I go with out.

 

[pickens]

CRITCIAL.

If you plan on running then engine over 4k RPM and expect it to last longer than 5K miles, then you need to balance it. This is a basic step in an engine rebuild that people should not skimp on.

 

[Drifter27_04]

CRITCIAL.

If you plan on running then engine over 4k RPM and expect it to last longer than 5K miles, then you need to balance it. This is a basic step in an engine rebuild that people should not skimp on.

Thank you,

For my info what is considered a proper balance? What parts should be balanced?
I have in mind the block,crank,pistons, rods, crank pulley, & flywheel. Is there anything else I am missing? My block is in the machine shop as we speak and waiting on my word. The only thing holding me back is the OEM crank pulley, I have to order one as the car I purchased came with a Unorthodox pulley.

 

[dnhieu]

CRITCIAL.

If you plan on running then engine over 4k RPM and expect it to last longer than 5K miles, then you need to balance it. This is a basic step in an engine rebuild that people should not skimp on.

THIS IS THE EXACT SAME THING THE GUY AT THE MACHINE SHOP TOLD ME TODAY! very critical to be done. especially if your getting a knife edge crank, aftermarket crank pulley, and aftermarket flywheel. the way i feel is that your going so far away from stock its almost necessary.

hope that helps
david

 

[dnhieu]

Thank you,

For my info what is considered a proper balance? What parts should be balanced?
I have in mind the block,crank,pistons, rods, crank pulley, & flywheel. Is there anything else I am missing? My block is in the machine shop as we speak and waiting on my word. The only thing holding me back is the OEM crank pulley, I have to order one as the car I purchased came with a Unorthodox pulley.

as far as the way my crank is getting balanced all i needed was the crank,flywheel,crank pulley, and all nesacary bolts that connect them all to the crank. i would KEEP the aftermarket crank pulley as it is lighter and will free up more hp in your motor. the only reason why i got a stock crank pulley was because i had a shitty ebay crank pulley and it keeps making my belts squeel on cold starts.

 

[Drifter27_04]

as far as the way my crank is getting balanced all i needed was the crank,flywheel,crank pulley, and all nesacary bolts that connect them all to the crank. i would KEEP the aftermarket crank pulley as it is lighter and will free up more hp in your motor. the only reason why i got a stock crank pulley was because i had a shitty ebay crank pulley and it keeps making my belts squeel on cold starts.

As for the light crank pulley I have dwelled on it and almost everyone I heard and talked with suggest to get a stock Harmonic Damper pulley. I have not heard anyone yet say they are running a light for ever and not had one single problem yet. Also in conclusion I am shooting for the 4-450whp mark so I thought going with the OEM pulley it would be better.

 

[dnhieu]

their is nothing wrong with the stock crank pulley making 400hp +++. most people dwell on the thought of using a crank pulley because its been knowing to crank walk a motor because it messes up the balance of the crank. if your getting a fully balanced rotating assembly YOU DO NOT HAVE TO WORRY ABOUT THIS because it will be bolted on and will be perfectly balanced as if it was stock. on the other note the stock crank pulley has its bad sides too! they are a two piece design and i had one fall apart on me blowing up my radiatior because it ran a little hot just trying to get it home. but in the end its your decision. if i were you i would keep the crank pulley and get that thing balanced on their

 

[Drifter27_04]

their is nothing wrong with the stock crank pulley making 400hp +++. most people dwell on the thought of using a crank pulley because its been knowing to crank walk a motor because it messes up the balance of the crank. if your getting a fully balanced rotating assembly YOU DO NOT HAVE TO WORRY ABOUT THIS because it will be bolted on and will be perfectly balanced as if it was stock. on the other note the stock crank pulley has its bad sides too! they are a two piece design and i had one fall apart on me blowing up my radiatior because it ran a little hot just trying to get it home. but in the end its your decision. if i were you i would keep the crank pulley and get that thing balanced on their

Thanks alot,

I will go with the light wieght than.

 

[pickens]

Balancing of an in-line four includes balancing: Pistons, rods, crank, flywheel, and the clutch assembly. For our engines, all rotating parts only need to be balanced individually and not as an assembly like V6's or V8's.

 

[Drifter27_04]

Balancing of an in-line four includes balancing: Pistons, rods, crank, flywheel, and the clutch assembly. For our engines, all rotating parts only need to be balanced individually and not as an assembly like V6's or V8's.

Not for sure what you are saying in which this is my first build. As I understand you are saying that they do not need to be assembled but wieghted out, is this correct? My understanding of balancing is taking everything and bolting them togather and having them rotated and from there they take a little here and a little there off to balance it all out.

 

[dnhieu]

hmmm.....why dont you talk to the guy that is doing your machine work. all the balancing machines that the guy showed me could just balance the crank and not the pistons and rods. ill talk to my guy on friday about the whole clutch thing. from what he told me you need everything that bolts to the crank and the block will not be included because the balancing machine just holds the crank. ill get back to you on the info!

 

[Drifter27_04]

hmmm.....why dont you talk to the guy that is doing your machine work. all the balancing machines that the guy showed me could just balance the crank and not the pistons and rods. ill talk to my guy on friday about the whole clutch thing. from what he told me you need everything that bolts to the crank and the block will not be included because the balancing machine just holds the crank. ill get back to you on the info!

Thanks man

 

[blue1]

You balance everything that rotates, what the use of doing the crank if the rods and pistons are all over the place, think about it! and the OEM damper is there to dampen the harmonics created by the crank flexing, take that away and cracks will appear eventually

 

[Defiant]

Any shop that does balancing will tell you what to bring in for the job. As them their thoughts on going without a harmonic balancer.

 

[gman991057]

defiant what kind of answer is that?? These guys are on here asking us what we think about their situations. The normal human being would go with what the machine shop guy tells them but some of us here need a little more confort from someone who knows a little more about the 4g63 motor or just 4 cylinders in general. DO you just go with what the mechanic tells you??? I dont

 

[Big Woo]

First off balancing is critical to engine life. V type engines and in-line engines are balanced differently. In V type engine a bob weight is determined by the number of cylinders in the engine, the degree of the V-angle and other factors not important here. These bob weights are then attached to the crankshaft throws to simulate the rotating and reciprocating weights influencing the crankshaft as is spins. (in a nut shell) In-line engines do not require a bob weight to be added to the crankshaft throws for balancing.

For a basic rotating assembly balance job you should bring the following. All pistons, connecting rods, crankshaft, harmonic balancer or front pulley, flywheel or flex plate, clutch pressure plate, all necessary bolts and fasteners, (at least one piston ring set, and a rod bearing for V engines).

The pistons will be weighed and corrected, and are 100% reciprocating weight. Connecting rods are different since they are partly rotating weight and partly reciprocating weight. The rods are weighed with a fixture that allows the big end (rotating weight) to be determined separately from the small end (reciprocating weight). Together they make up the entire rod weight. The crankshaft is placed on a machine that indicates and measures imbalance both kinetically and dynamically. Once the crankshaft is balanced items like the flywheel and front pulley can be added and balanced.

Do not think that a underdrive front pulley is a harmonic balancer, that would be like comparing an axe to a jump rope. An underdrive front pulley may decrease rotating weight, but it will do nothing to dampen harmonic vibrations, and may lead to bearing fatigue problems. Please remember that your engine will still create harmonic vibrations, even after having it balanced, as the two are completely separate issues.

 

[dnhieu]

i talked to the guy at the machine shop the other day and he said idealy you want the clutch to go with it. but its not as important because alot of the time they come pre balanced. he told me since im running upgraded pistons and rods that they also come prebalance within a few grams (he showed me on the ross and eagle boxes). these pistons and rods come way more balanced then mitsu could ever do with their factory pistons and rods. is all this info true???

thanks
david

 

[dnhieu]

oOo yeah i correct myself my ross pistons and eagle rods are getting balanced with my crank. sorry to confuse everyone.

 

[BrokenTsi]

in reality, its not very critical to balance your rotating assembly.

Wiseco pistons come matched extremely closely, usually to within .1 gram.
Eagle rods etc usually come matched to within 1 gram.
Stock crank is extremely well balanced from the factory.

In most cases, these shops will charge you and not touch the items. Call AMS or anyone and ask if they balance a stock crank. Theyll tell you its not worth it.

And you also run the risk of the shops equipment not being calibrated correctly and screwing them up.

So in other words, really not necessary with aftermarket internals.

 

[kiggly]

I've never balanced a crank, nor have I ever had any material cut off one. Its good to balance all the parts to each other, but as previously stated, they usually don't vary much at all. I just balance the pistons to each other and run it. I had several seasons on a 2.0l going to 9.5k like this and about 40 passes and 20 dyno pulls on a 2.3l going to 9k (other changes are req'd on a 2.3l at these rpm's).

I would highly recommend using a stock damper. Almost all stories of broken cranks are accompanied by aftermarket underdrive pulleys and improper crank resizing.

Kevin

 

[raped]

I've never balanced a crank, nor have I ever had any material cut off one. Its good to balance all the parts to each other, but as previously stated, they usually don't vary much at all. I just balance the pistons to each other and run it. I had several seasons on a 2.0l going to 9.5k like this and about 40 passes and 20 dyno pulls on a 2.3l going to 9k (other changes are req'd on a 2.3l at these rpm's).

I would highly recommend using a stock damper. Almost all stories of broken cranks are accompanied by aftermarket underdrive pulleys and improper crank resizing.

Kevin

Kevin-
could you elaborate on improper crank resizing. I assume you are talking about cutting a crank for use with oversize bearings but exactly what can be done incorrectly.
secondly what other changes are required to rev a 2.3 to 9k? from what I have heard reving that high on a 2.3 can cause rod bearing wear or failure.

Thanks!

 

[BrokenTsi]

cutting a crank is very precise work.. the better question is, what cant go wrong? Ive seen a good amount of cut cranks have the journals not end up being perfectly round etc.

 

[raped]

I ask because I have had issues with crank failure on a buddies car that I built. the crank was cut .010 under each time and broke twice.

 

[Defiant]

DSM crankshafts are non-serviceable. If out of spec, they are to be replaced.

 

[dnhieu]

also i had my balanced rotating assembly with this crank that has been shaved down if that helps at all. how can you tell if the crank has been improperly shaved down? when i look at it, it seems perfectly fine and the grooves feel nice a smooth. any info would help.

thanks
david