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.

 

[Wikkedson]

I have heard that they come pretty balanced to begin with.
But if you have the money then what would it hurt to get it balanced? I say go for it.

 

[BooSTEDblue]

when u remove the balance shafts no vibration is made, more is just felt....Take a look at www.roadraceengineering.com for the pros/cons of the removal.

 

[Stock90GSXT]

Originally posted by BooSTEDblue
when u remove the balance shafts no vibration is made, more is just felt....Take a look at www.roadraceengineering.com for the pros/cons of the removal.

ya, I read that too. i was talking to my machine shop and he said if you take to much off the rods (I.E making them fit 95 pistons) they MIGHT have to be balanced. it costs 150 bucks to balance it, if i can save that. I won't do it. This is somewhat of a budget build up, but im trying not to cut to much corners. I can get 95 pistons new with rings (aftermarket) for 120 bucks a set. They are OEM quality and are suppose to be moly coated.

 

[rdrkt]

You don’t need to remove the engine to eliminate the bshafts. If you don’t have to rebuild the engine don’t. If you are pulling the motor out then yes you should send out your pistons, rods, crankshaft, and flywheel. The biggest benefits will not be in the vibration that you are don’t feel it will be in increased engine life and quicker revs.

 

[hose101772]

do believe the hype-balance is crutial for long engine life.GOT BALANCE-you'll wish you did.good luck with the rebuild.

 

[dsm_dan]

Rods are at machine shop now getting narrowed and pin bore honed out 1mm to get it to 22mm for 2g pistons . Can this be installed without balancing the rotating assembly??... since the rods are not to "oem" specifications... Or will the setup be just fine. also ring gap clearance.... opinions on this? What is a good gap... ive seen scored walls from too little a gap... any comments?

heres the set up:

stock rods machined to fit 2 g pistons
new rings
stock block, un bored
stock crank , uncut
clevite 77 main and rod bearings
stock headgasket
balance shaft REMOVED


all help is much appreciated

 

[mrmadmax]

Originally posted by dsm_dan
Rods are at machine shop now getting narrowed and pin bore honed out 1mm to get it to 22mm for 2g pistons . Can this be installed without balancing the rotating assembly??... since the rods are not to "oem" specifications... Or will the setup be just fine. also ring gap clearance.... opinions on this? What is a good gap... ive seen scored walls from too little a gap... any comments?

...

all help is much appreciated

Well, to answer your question, there is no problem with simply balancing the the rods to each other, and the pistons to each other as well (balance with piston pin with the piston). Just remember to write down all the numbers before you put it all together. That way, if you ever have to replace a part, you don't have to rebalance everything.

Balancing V-engines is a different story, because you have to calculate a weight to put on the crank based on the piston and rod. We don't have to worry about that.

The question is, why would you NOT balance the rotating assembly? Everytime I bring in a motor to be balanced, I bring in the crank, pulleys, cam sprockets, flywheel, pressure plate, all bolts etc. You should see how far out of balance a new ACT pressure plate is! (maybe I got a bad one)

As for the ring gap, I shot for the middle of the range, and all's well--but on the other hand I don't run over 15 psi boost. Maybe someone else can chime in? (someone that has actually seen ring gap related problems)

 

[1gTURD]

Hey, I posted this up on my buddies name (dsm dan) by accident, he wa slogged into my computer.... anyways

the reason i didnt want to balance is because i have the crank in teh car along with the block and trans... i just popped out the rods and pistons after taking the head off...

Basically i just want to know if I could cause any damage by not putting the rods and new pistons in without balancing the rotating assemly ( set up as listed above)
Reason for this is, the car has been off the road for quite some time and i need it back asap... pulling the crank and trans and flywheel back off would set me back a couple days because of lack of Air... I would have to resort to hand tools in my driveway unless i buy another compressor and tank, wich isnt in my budget right now. I am a Subaru tech at a dealership but the tow to my work is also out of my budget... however if the r-assembly has to be balanced, then I guess it has to be balanced...

as far as the ring gap goes, I think I should be ok but does anyone have any ring gap specs they can shoot my way...

Thanks for the input and any more info would be greatly apreciated! Thanks again

 

[GalantVR41062]

Would the motor balance its self? 2 pistons are up and 2 pistons are down and as long as the piston and rod combos weight the same it would be balanced.

 

[mrmadmax]

Originally posted by GalantVR41062
Would the motor balance its self? 2 pistons are up and 2 pistons are down and as long as the piston and rod combos weight the same it would be balanced.

Yeah, that's what I was was saying (in so many words) above. As long as all the pistons/pins have athe same mass, and the rods have the same mass/big end weight, all's well with the balance (for a four cylinder inline engine).

1gTURD: Yeah, that makes a lot more sense. You'll be fine by not balancing the rotating assembly because of your time/budget. I was thinking you had it all out of the car.

 

[germain101]

while you're at it, you should have the machine shop grind off the factory casting marks on the sides of the rods...this will reduce a little weight and also make the rods a little stronger...

 

[AdrenilineCrash]

what is it? i know i have no mods except an intake so please dont say "your car dosent have any mods."

what is it? i read about it in some members mod llist. it said competition balanced to 9500. does that mean he had his "redline" raised to 9500 or what?

-mike

 

[greathuskie]

i BELIEVE it means his cars rotating assembly is balanced to safely rev to 9500 without problem

 

[chaye]

hey 1gturd what is up..question..
im going to do the samething that you did install a 6bolt soon as i find one..and i have been debating wether i should install stock pistons or go for the 2g pistons.but i too run on a budget..
so my questions are..
how much did the shop charge u to machine the rods and piston wrist
and what boost levels will you be runing thanks man..
good luck

 

[GalantVR41062]

The 1g pistons have put 400-450whp down with N20(turbo mag did up a Galant VR-4) and the 2g piston rod combo don't seem to like over 500-550ish(I think). I say 1g pistons and build the motor right, later, if you looking for that kind of power. And removing stress risers on the rods and pistons will greatly increase strength, along with shot peen and polish. If there is no place for a crack to start the part is that much stronger. Good luck with your motor.

 

[1gTURD]

well its been done for a few days now.
Shop charged 192.00 (with tax) to do the rods, pop the pistons on a nd also balance the rods themselves to "0" g


the car moves like a bat out of hell... very impressed with the way it turned out , however today i blew a hole in a ic pipe connector and had a nice boost leak... so @ 10-15 psi (on teh guage) the turbo was actually spooling enough rpms to spin off the damned impellar shaft.... so now im gonna upgrade the spanked turbo. But i really do reccomend pistons of some sort... even with pump gas and stock base 5-3 degrees btdc timing i get no knock

(510 cc injectors and safc)
really satisfied with teh setup.... cheap and easy... just the way i like it

 

[chaye]

so then it runs way better with the 2g pistons....so the knock is cause by the lower copression? this is why 2g pistons on a 6bolt motor is best?
thanks

 

[allwheelTSI]

Originally posted by chaye
so then it runs way better with the 2g pistons....so the knock is cause by the lower copression? this is why 2g pistons on a 6bolt motor is best?
thanks

actually,higher compression pistons are more likely to cause knock because of the increased cylinder pressures,the reason why we put them on big rods is because the higher compression spools the turbo quicker and gives a little horsepower gain.

 

[1fast97gsx]

what exactly is the point of it and when is it ABSOLUTLY necessary? What are the benefits of it? What all gets balanced? Thanks.

 

[MNGSX]

It is'nt absolutely necessary.

On an inline four you can do 99% of the work yourself with a gram scale.

Just have a machine shop do the crank the crank counterweights need to weight the same.

For the rods.

Factory rods.

Have a machine shop install ARP rod bolts, resize and balance them.
I have done rods myself. It is'nt impossible. Basically find the lightest big end and file the rest to match at the appropriate place on the rod in the right direction. Then do the same with the small end.

If I had rods at a shop for other work and you should (bolts and resize) just have them do it.

If you have aftermarket rods they are nearly always sold in weight matched sets of four with ARP fasteners already. So the rods are good.

Factory cast pistons just throw them on the scale and find the lightest. On the other three just take material off from above the wrist pin boss equally on each side.

Aftermarket forged pistons. Several HQ forged piston MFGs usually have such high QC that they are all almost exactly the same weight already.

If the machine shop says they can't balance a inline four crank without the rods and pistons they have been doing V8s for too long.

On inline fours everything just has to weight the same. Dynamic balancing does'nt matter like it does with v8's

Having a stock flywheel done by a machine shop might help too. They are balanced at the factory. If more work is done depends on the shops QC. Those need to be spun and spun by themselves for our engines. Its more like spin balancing a tire with the flywheel than anything else I can compare it too.

An aftermarket flywheel like a ACT or a fidcrapza should be perfect.

 

[1fast97gsx]

ok cool. I will be replacing pistons with JE and rods with Eagle rods so I should be set. Thanks.

 

[MNGSX]

I'd check the JE's.

I have a had Ross and Arias come out so equal the scale could'nt tell.

I have'nt assembled and engine with JE's that was'nt a V8 and the machinist balanced. I do think a very small mount of adjustment was neccessary. They were'nt really far off from each other.

 

[1fast97gsx]

ok I see. Well what are the side affects of not balancing anything and just throwing it all together? I'm not going to do this but I'm just wondering what a worst case or average case scenario would be... thanks.

 

[MNGSX]

Actually the factory was OK on the cranks.

With the JE's you are probably within tighter tolerances than any factory part.

The rods you have should be dead on.

With the parts you have you should be damn close w/o balancing.

I'd just have the crank and flywheel done..

Borrow an accurate gram scale and check the piston weights...

WITH PINS AND RINGS...

pair up a piston with corresponding a pin and a ring set.

Weight the pins first. Sometimes you can iron out piston weight differences by putting the heavy pin on the light piston etc...

Like I said with what you have you are 75% there anyway.