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.

 

[1fast97gsx]

oh .. I have a fidanza flywheel as well. No need to mess with that?

 

[GT40MkI]

Ok, I'm learning about this whole inline 4 thing, been raised on OHV v8's and am a bit confused.

Here is my predicament. I'm buying a set of Eagle rods from a VERY knowledgable friend...My shortblock currently is a mid 80s 6 bolt 4g64 with weisco dish pistons and 1g big rods.

I realize that the pistons are all balanced to each other.
I realize that the eagle rods (I know this is a touchy subject) SHOULD be balanced to each other from Eagle.

Now this is the part that confuses me. On a v8 application you weigh EVERYTHING, big end and small end of the rods, the wristpins, the pistons, etc and match it all as close as possible. The you get a bob-weight. You spin the crank with the bob weight until it spins true.

I would normally assume the same to be the case for an inline 4, as the crank is counterweighted to the factory reciprocating assy.

HOWEVER, we have these wonderful balance shafts. What is the function? Can I expect the balance shaft to compensate for the imbalance in the rotating assembly? Should I try and get a new "weight" shaft?


I'm claiming ignorance and if I'm pulling the engine apart to swap rods I'd like to do it right. Please refrain from the "eagle is junk" comments, but any info/experience/comment is welcome.


-Sean

 

[thegreatms]

......Am i having de sha vu? I think i just read this,


Oh, wait i did just read this on the other board...

 

[aero_sallee]

I removed the balance shafts on my new 7 bolt '64 motor. I am running that with an eagle/wiseco combo. I had it balanced and I don't notice any more vibration than the stock motor had WITH balance shafts. This is even with the longer stroke. I would definitly get the whole rotating assembly balanced. The balance shafts are mostly a liability anyway.

 

[bjones18]

Balance shafts are not used to counter act "mass" differences in the engine. Apparently Mitsu balances their internals pretty well (I asked a reputable builder about balancing...he said you only have to worry about up down, and mitsu does a pretty good job at that).

Balance shafts are used to counteract "natural" resonances in the engine at specific RPMs. If it idles rough, the average customer thinks something is wrong. Generally the customers viewing this forum don't care about a little NVH (noise, vibration, harshness)

To the people who read this forum, balance shafts are designed to cause premature engine failure, and therefore many remove them using "kits" or similar hardware.

As an example, I purchased two engines last week. One, a casualty of a broken timing belt (bent valves). Upon disassembly the oil pump was difficult to turn, and tought to remove the oil pump front cover. It turns out the rear balance shaft spun a bearing and locked it to the shaft, thus the bearing was rotating with the shaft; friction surface between the block and bearing. Apparently this broke the timing belt and sent the #2 piston into the valves.

The rear balance shaft is connected to one of the oil pump gears, and therefore a spun bearing makes it tough to rotate the oil pump. The shaft comes off with the oil pump housing. Of course this is true until you eliminate the balance shafts.

Do as you wish, but after seeing this, I will never assemble a 4G63 with balance shafts

 

[GT40MkI]

Thanks for the info...

So, technically I'd be ok just installing the rods and putting back together, although the preferred method would be to have the assembly balanced and eliminate the balance shafts...right?


-Sean

 

[2.4 turbo Hyped]

Thanks for the info...

So, technically I'd be ok just installing the rods and putting back together, although the preferred method would be to have the assembly balanced and eliminate the balance shafts...right?


-Sean

Are you running a g4cs block? I have the same setup you are building. Wiseco 8.8:1 pistons and 1g eagle rods. I never had mine balanced and it runs perfectly fine - phantom knock but thats a whole other story.

 

[bjones18]

Thanks for the info...

So, technically I'd be ok just installing the rods and putting back together, although the preferred method would be to have the assembly balanced and eliminate the balance shafts...right?


-Sean

re-read the note above...the balance shafts are not designed to counter act mass imbalance in the pistons/rods/crank.

 

[SpoolinGSX]

In an inline engine you don't use bobweights when balancing. All you do is make sure the small ends match each other, the big ends match each other and the pistons match each other. Balance to within 1 gram. As long as you have the engine out just get rid of those balance shafts as stated in the above posts.

 

[GT40MkI]

Awesome...thanks for all the posts....sorry I wasn't too clear with the question, I just can't seem to comprehend having all the forces on a single plane with the crank spinning in a circle!


LoL

 

[killab443]

How exactly do they balance an engine? With forged internals? Were do they add/take out weight to balance it right

 

[oddrob]

Usually they will drill the counterweights of the crankshaft.

 

[blackGSX2g]

When rods are balanced, they weigh both the big end and small end and grind off a little bit at a time to get them within the acceptable tolerances. If you look at your crankshaft you will see drill holes in the counter weights as posted.

 

[killab443]

do they take the crank out to balance it?

 

[FireyIce01]

yes they take it out

 

[4wd-Eclipse]

Sometimes they used to GRIND (not drill) the counterweights of the crankshaft.


MK

 

[keltalon]

just let me tell u this it is very necessary!! check out this thread it explains it better than i can!

http://www.centuryperformance.com/balancing.asp

 

[keltalon]

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

very well said


http://www.centuryperformance.com/balancing.asp

 

[pickens]

I have some concerns about balancing a 4g63 engine since it is externally balanced. To balance our engines you need to have the flywheel/Pressure plate and harmonic dampner balanced w/ the crank, pistons, etc. So, if you balance an eninge during a rebuild, but then change the flywheel, pressure plate, or harmonic dampner a few years down the road, what happens to the overall engine balance? I would think since the new part wasn't balanced w/ the other parts, the overall balance would be off. How would you be able to ensure the new part(s) will be in balance w/ engine?

 

[steve]

I have some concerns about balancing a 4g63 engine since it is externally balanced.

What makes you think that?

Steve

 

[bullettdsm]

I have some concerns about balancing a 4g63 engine since it is externally balanced. To balance our engines you need to have the flywheel/Pressure plate and harmonic dampner balanced w/ the crank, pistons, etc. So, if you balance an eninge during a rebuild, but then change the flywheel, pressure plate, or harmonic dampner a few years down the road, what happens to the overall engine balance? I would think since the new part wasn't balanced w/ the other parts, the overall balance would be off. How would you be able to ensure the new part(s) will be in balance w/ engine?

No, not true. Don't worry and feel free to balance your engine.
MB

 

[engineman100]

balance it without the flywheel and clutch pack , then if you feel the need to fine tune the balance balance the pack and flywheel on an short arbour independent from the crank, this will allow you to replace bad assemblies later. www.overbore.com for mitsu balance information.180.00 for this service.
thanks

 

[7boltnewbie]

I am planning on upgrading my engine with eagle rods and je or arias pistons. I was told by one person that I have to get my whole rotating assembly balanced if i change these parts. I was also told by another person that it is not necessary unless I plan on building an all out race car. I plan on using this as a daily driver in the neighborhood of 300-400 hp. Both of these guys have experience with building sbc engines but not 4 cyl. Anyone here that has real experience with building these engines that could give me insight on what I should do, it would be appreciated. Thanks in advance.

 

[MNGSX]

Its the most misunderstood and urban legend/speed shop scam end of engine building.

An inline four really needs to have matching weights for all rods and pistons. It is about 10,000x simpler than on V6/V8/V10/V12 etc engines.

That is what it comes down to.

Any aftermarket rod set worth buying will be weight matched meaning the every big (crank) end and every small (piston pin) end weights the same... They will also have ARP cap screws.

So with aftermarket rods you are done with rod balancing just by buying them .

Now we need to get all four piston assemblys (piston pins and ring pack)
Get WISECO PISTONS..... BEST pistons available for 4g63's......

You wont get piston slap when cold due to the offset wrist pin (JE does'nt) and tighter piston wall clearances. They have a better alloy for turbo engines than arias. They have the most consistent weight tolerances as well meaning its easy to get them to weight the same.


Our cranks are plenty close enough as it is. A shop CAN and SHOULD balance the crank on a inline four by its lonesome.

A good aftermarket flywheel and clutch will be dead on from the factory.


http://www.babcox.com/editorial/ar/eb10330.htm

With inline four and six cylinder engines, and flat horizontally opposed fours and sixes (like Porsche and Subaru), all pistons move back and forth in the same plane and are typically phased 180° apart so crankshaft counterweights are not needed to balance the reciprocating components. Balance can be achieved by carefully weighing all the pistons, rods, wrist pins, rings and bearings, then equalizing them to the lightest weight.

Buy the right parts and you can balance a inline 4 like a 4g63 with a hand file and a gram scale.

http://www.dsmtuners.com/forums/showthread.php?t=111079&page=2&pp=25&highlight=Wiseco+Piston+Weight

I ended up using Wiseco's as well recently, mainly due to Brian Nutter's active appearance in these DSM forums. Their design looks better than the Ross's I had: Extra oiling grooves above the top ring land, reinforcement of the piston forged in, thinner upper compression ring, coated skirts, lighter weight, and less variance in that weight. Pretty much make the Ross's look like generic piston 101. Oh, and the weights were 336.4, 336.4, 336.4, and 336.0, for a variance of 0.4 grams. Ross says their pistons vary at the most by 2.5 grams . Here's a pic of the Wiseco's I put in my engine:

WOW
336.4, 336.4, 336.4, and 336.0...

.4 grams "needs" to be removed from three pistons in this case. Its so close it probably does'nt matter. You could also do it by taking weight off the wrist pin that goes with that piston. I did one motor for hire and all 4 pistons came out to be within a .2 range. I weighed the wrist pins and was able to zero even them out to about .1gram by puting the right wrist pin with each piston. That is a .0035 ounce difference... I did'nt have to remove weight from anything. Really expensive oliver rods have a max .5g weight tolerance so i dont think that .1g at the piston assembly matters too much.

IMHO

Buy Wiseco pistons and eagle rods then Just have the crank checked and the journals micropolished only with no regrind. Want better rods get olivers or something. But look at the dynos and Ets for properly built eagle rod engines.... Seems to be good enough for 99.99% of people.

Basically HQ rods + HQ pistons = put it together & its balanced.

Have extra money to burn just have the cranks own individual balance checked and corrected if need be.... Basically that opposing counterweights match each other. A machinist freind did that for free for me...

As for things like the flywheel & clutch get an aftermarket and it is dead on too. Basically balancing a flywheel is like a tire on a inline four. No one area should be heavier than the other. A aftermarket ACT or a SSG billet aluminum will be dead fn on out the box.

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.

 

[Nanan]

Get the engine balanced, blue-printed, and the crank knife edged, it will last longer as it will vibrate less. What you are doing is removing the inconsistancies of production by making each piece fit the same spec and weight. Your engine will last longer as it will have less vibration and it will in general perform better and hold together longer at high rpm.