To Balance or Not to Balance

[TheDarkRaver]

Ok I thought I might post this up to see what opinion some others have on the subject as I have been getting some very mixed responses from various ppl..

I am at the moment building up a 7MGTE to make (hopefully) between 320-350rwkws.. The engine is currently at the machine shop as it has just been bored out .5mm to fit a new set of forged pistons in..

Now while it is at the shop (getting a few other bits done) should I fork out the $270 odd dollars I was quoted to have the bottom end balance (from harmonic balancer to flywheel and pressure plate). Keeping in mind before the car was stripped down the motor was running fine and the only change has been the addition of the forged pistons (which I have weighed and are all matched in weight to within .002 of a gram..)

For that money I kind of see it as a pointless (could be very wrong) exercise as the motors come balance from the factory..

I know I am going to get alot of people saying I should do it but I need to hear some reasoning to convince me, not just if you are spending big $$$ on the motor already you are mad not to..

Any way thanks to anyone that post's a reply up and has a say!

Marc,

[1jzracing]

welll i recon you really answered it yourself

balance IS critical but modern engines are near perfect from the factory so if the new pistons are matched so well then i would not bother

really depends on the intended use of the enging if it was a circuit racer i would spent the extra few bucks and get it checked but for a street / weekend warior then it'l be fine

[Sprinterboy]

$270 vs complete rebuild again........

i'd do it just for peice of mind and one less thing to worry about, sure it's almost 300 dollars now, but at the end of the day, cars will always cost money

[30psi 4agte]

If you are even questioning this means you know it needs to be done but cant justify the cost .

Get it done as its worth it. If you want that sort of hp its gonna need rpm so every bit counts.

DONT SKIMP YOULL REGRET IT !!

[thechuckster]

factory balance is not a dynamic balance of the whole crank+rods+pistons+flywheel+pulleys+p/plate - the only thing that gets that is the actual crank, the rest are matched for weight.

[Hurricane]

YES DO IT FOR SURE i did it and it did make a dif to the engine, it reved out more and alot cleaner also and yeah just seemed better.

i know that most cars are said to be pritty good balanced from stock and the jap cars are better than some, but al the shops i have talked to said that there have done some new and newish balance jobs on them and they got them alot better on ther machine

[1jzracing]

in the old days factory balance was crap but engines today ARE dynamically belenced just look at the front pully, flywheel, even clutch and it will have drilling marks on it

i have done heaps of engines some balanced and some not and for a road engine that has all original parts in the right order its not gonna make an ounce of difference

i only get it done if im swaping components around like rods and flywheels etc

[Sam_Q]

and during what time period do you think things started to change for toyots engines? I heard 4ag engines are suprisingly out of balance for the revs they pull

[YelloRolla]

I think that the point is that the state of balance is unknown until it is checked and then either balanced or left alone.

All this speculation about engines past and how good Toyota does them etc tells you nothing about your engine.

If it is a serious engine build (that is if you are serious about it) then get it done, without question.

[jeffro ra28]

You would be suprised. The japs have nailed their technology. I doubt anyone here in Australia could beat the factory balance of a jap motor anyway. I work with billet cranks, rods and forged pistons every day. Rotating assemblies worth over 10,000 just in crank rods and pistons. I decided not to balance my 1uz motor because i know how good the japs are at what they do. BUT, i am using all stock parts in the bottom end, so, no weight change.

If you change the weight of any part connected to the crank, then balancing is required. So if the piston weight is different to that of standard, the crank should be re balanced to the new weights.

[trd3sg]

definitely do it - the fact that the new pistons you have now installed with the new bore will be a factory cast is enough reason - ie that the pistons themselves will be differing in their weight from factory

Furthermore, to compensate for any additional stress that the overbore has put on the block, the balancing will eradicate vibrations that are "potentially" threatening to the sturdiness of the bottom end

Not to mention the extra 200-400 rpm you will safely extract in the upper rev limit of the motor to create that bit more potential power, or even extend your safety barrier if you are retaining the same rev limit

[trd3sg]

You would be suprised. The japs have nailed their technology. I doubt anyone here in Australia could beat the factory balance of a jap motor anyway. I work with billet cranks, rods and forged pistons every day. Rotating assemblies worth over 10,000 just in crank rods and pistons. I decided not to balance my 1uz motor because i know how good the japs are at what they do. BUT, i am using all stock parts in the bottom end, so, no weight change.

If you change the weight of any part connected to the crank, then balancing is required. So if the piston weight is different to that of standard, the crank should be re balanced to the new weights.

doh ! you just beat me to it lol

[GasedT18]

the only change has been the addition of the forged pistons (which I have weighed and are all matched in weight to within .002 of a gram..)

2 mg eh? And what is the difference in weight between the original and forged pistons - are you using same pins etc?

[1jzracing]

you only have to take the actual piston or rod weight into consideration when balancing "V" engines

... otherwise they just need to be matched for all inline motors there is no relivance to crank balancing

[TopSecret]

and during what time period do you think things started to change for toyots engines? I heard 4ag engines are suprisingly out of balance for the revs they pull

Very little was done to my 4AG rods and flywheel, though the crank had some pretty significant drillings in it when it was all balanced.