LOL

Sorry but thats kind of funny.

 

Nothing could be more true. Unless, of course, you pay a shop to custom balance the pistons to the exact weight of the stockers, but that would require a major reduction in piston strength. Forged aluminum is very heavy, and removing weight would mean removing material therefore sacrificing strength.

The other option is to pay a piston company to custom build/machine forged pistons to the exact weight of the stockers. But again, I would think you'd compromise strength.

It would also be expensive to have mallory metal added to the stock crank to match the weight of the forged pistons, since they're probably considerably heavier than the stock cast pistons.

You'd really have to do your homework to find out which is most effective from a dollar/reliability stand point.

 

well Brian, then you are telling GM Performance and their engineers that you are right and they are wrong!

Maybe you should read some of the literature they put out huh?

I personally have done it and have had NO problems at all with both 1 of which was mine and 1 which was a bud's car and plan on doing something similar to my 2.0 very soon....

They GMPP even go as far as to use 2.0L Forged rods in the engine and forged pistons with the old bearings from each cylinder and the rings...

 

It's happened before..

I'm telling you that the crank is supposed to be balanced for the weight of the piston.

You might think that if you change all the pistons that the weight will simply cancel out because they are all heavier or lighter. The crank is supposed to be balanced to offset the exact rotating weight of the pistons and rods... This prevents harmonic inbalance which will cause minute shockwaves to act on the main supports and eventually cause crankwalk. This will be accentuated at upper RPM levels.

The 2.0 is a SAAB motor so I'm very confident that they have worked a crank balance into the original design of the motor.



Ok, seriously.... **** it. Put whatever you want into your car. It not my problem, I have a fully balanced rotating assembly because it's how it has to be.. You have whatever you installed... however you installed.

I can't believe the level of blind trust you put into a car company. Seriously, if your car blows up, do you think they really care? Will they fix it? No, you will buy more parts from them. They want it to seem like easy installs are perfect and qualify as a proper built motor so You will buy their parts and install them.

 

Amen to that.

 

Nope. Crank counterbalances are for the crank and small portion of the connecting rod only. You would be trying to counterbalance vertical motion with rotating mass. Imagine the stresses that would occur on the crank as those heavier counterweights traveled side to side as the piston is halfway through a stroke.

 

My Bad, I will admit a typo. I wrote Piston, but meant to say internals.

 

What I was trying to say is changing only the pistons will not have an effect on crank balancing. As long as all pistons weigh the same, their mass will indeed cancel each other out. What you described earlier applies to "V" configuration engines only.

 

I strongly agree with this comment! if you plan on running this enginge up to redline you definately want to balance the rotating assembly or risk getting a severe vibration at higher RPM's. i would also recommend getting the cylinders honed and new rings installed. i would never reuse piston rings either! they are cheap and a good set of rings can go a long way to making your engine reliable for years to come.

 

if you use new piston rings you must get them all honed. if you reuse the rings no.

 

Our crankshafts are balanced quite well as is. Rings, eh, everyone has their own opinion on that.

 

I think Brian was talking about balancing as far as dealing with the new pistons cause of them being forged (heavier).

 

Yeah, thats what I was saying, changing pistons does not require crank balancing on an inline motor. He had our motors confused with a "V" configuration.

 

i still say balance the whole assembly! i guarantee if you weigh the pistons each will weigh a differant amount. mayby not enough to notice but enough to cause some vibration (maybe not even noticable) which over time will take it's toll on your internals. the way i look at things you should do it one and do it right and never have to do it again (unless you want to).

 

For as much as they cost for our motor they better not weigh a different amount.

Most engine vibrations from an ecotec are caused by acceleration differences in the connecting rods/pistons. Those are handled by balance shafts spinning twice as fast as engine rpm. GM even reccomends removing the balance shafts to free up horsepower because the vibration dampened by them is within acceptable operating limits.

 

i'd be willing to bet they weigh a differant amount. even if it's a gram! no machine can make something EXACT every time. differant pieces of metal weigh differantly even though they are the same kind of metal. how much of a differance do you think a gram differance per piston makes a 7200 RPM's?

 

Pistons are balanced before you buy them.

 

who do you think is more careful balancing your ****? you or the guy standing on an assemply line for 8 hours a day getting paid 8 bucks an hour?

 

The guy that does it for a career. Also as far as tolerances, .5 gram difference is considered within acceptable weight limits

 

that's fine you do as you wish with you motor! i'm not trying to argue with you. it's your car feel free to break it! All i'm trying to say is that the guy who balances the pistons as a "career" doesn't give a **** if your motor ****** breaks! if you want to trust him go for it! he's not going to replace your motor when it brakes! the only person you can truely trust to do something correctly is yourself. i would NEVER build a motor with the intention of making serious power/racing without balancing the ENTIRE rotating assembly (crank, rods, pistons, EVERYTHING)! Ask anyone who knows anything about building performance motors what one of the first things they would do before assembling the motor is regardless of the configuration "V" or "inline"! if you want to build a reliable performance motor you balance everything, get all the serfices that need to be true and flat milled, hone the cylinders, stress test everything, etc.. I'm not debating that the pistons SHOULD all be equal BUT realistically are they? NO! there is no downside to taking the time to balance your rotating assembly. but there is potentially a downside to trusting a manufacturer. they won't pay for your motor when it breaks so i would double and triple check everything! i'm simply saying that when you are building a performance motor NOTHING should go unchecked! because rest assured the part you don't think needs checked and you proceed without checking it will undoubtedly be what breaks at the track or when you're racing a ****** honda with a snot nosed punk kid who has more piercings than brain cells driving it.

 

I trust JE, Wiseco, Diamond, etc to be able to match stock weights and balance within tolerances. They wouldn't be in business for so long if they couldn't. I myself would never weigh and balance new aftermaket pistons. Seems like a complete waste of time. To each his own I guess.

 

0.5 Grams is not acceptable in my ******* engine buddy..

Well then your opinion is really counterproductive here.

The person is trying to ask what he should do to his car to build it up so it will not fail again. Making a tuned built motor is expensive, that is why there are some people who simply don't do it, modifying a car is normally a part of your life. You choose to sacrifice some things to pay for the modifications you make. Why the hell do you think cars like mine are in Mags and Papers? Because most of the people who read about cars respect the effort and attention to detail that some people do to their cars. I can honestly say that there is nothing I could have done more to the motor in the Mazda, it is rated to hold 500 CHP, if it blows up it was my fault, not engine. I do not worry about hurting it over hard runs, because it was built to uncompromising tolerances. The CP pistons were in fact a balanced set, the postal scale did not have the accuracy to detect any differences in the pistons, the Olliver rods are know throughout the world by tuners as the definitive holy grail of perfection. They were only $1200.00

Dunk, Align honing, Deck Mill Head Mill, Bore, Crank True, Knifes Edge, Crank Balance. Cost me only $800. New Gaskets and hardware, $200.00

Assembly would have cost $500.00 +++

I chose to do that myself because I felt confident that I could do a better more deliberate job than the shop could, it was fun and it saved me the money.

Basically, DO NOT GHETTO OUT. It is a modified motor. It should be treated with the same level and precision as a snipers riffle. Assembled with no compromise and absolute deliberate care.

 

Yes. I stand corrected.

Then you should remove the oil from your engine. Oil that rides along on the pistons/rods can vary the weight more than .5 gram.

Here's a good read I found on balancing.

http://www.rpmmachine.com/engine-balancing.shtml

 

The oil is uniform across all four pistons. My engine has 4 oilers under the pistons that shoot a contant stream on the underside of the pistons. Your statement is not helpful at all, we are talking about the initial build of the engine, not variables that are out of our control. The reality is that if the tolerance is allowed to be loose, then when variables such as your oil theory come into play, they accentuate the problem.

Minimize the variation.

 

http://www.rpmmachine.com/engine-balancing.shtml

Aj, Your link was helpful however. Word UP!