What exactly is engine balancing? Shouldn't the engien already be balanced, sounds weird to me that it isn't.

Who does this job?

How much does it generally cost?

This is for a NA car.

Thanks,
Victor

 

I suggest you not balance the engine or waste the money. there are two types of balance. internal and external. The engine in your Z doesn't really have true balance, but the cranks are balanced, rods are matched sets, and the pistons have very tight weight specification. this is the same with many toyotas and hondas. The Japanese are very good at tight specs.

 

I'm not gonna do it. Just curiosity.

 

I think engine balancing is all about precision. For example, are each and every piston +/- 0.01 grams or +/- 0.001 grams different from each other? The closer in mass each one is, the less stress it is on the engine as you rev higher.

I think some of the benifits of a more balanced engine are longer engine life, able to handle more power, higher reving, smoother operation.

I heard from a friend that the reason Honda's inline-4's are so well built is because their cranks are extremely well balanced for each engine's slight imperfect balances.

I bet the cost to do such a mod would be rather expensive for the amount of benefit it would return. Again, this is one of those NA mods best left to the those exoticly rich. 8...(

 

You don't have to be rich to mod a NA engine. You don't have to be rich to balance a motor. But you should have a need to do it. Our race motors are balanced and blueprinted. Key word race. Street motor, not really necessary. Maybe if you went turbo or something on the street with really high boost and high RPM's it would be nice to do. An Injen and a Borla are not grounds for a B&B of the motor.

 

Yeah... much of the 700+ HP Supras here are well balance... the efficiency of the engine is impressive!

 

If you have the engine out of the car for a buildup I would definitely have it done. It doesn't cost that much more after you have the engine apart and it is well worth it. The 455 in my Skylark is balanced/blueprinted and it is incredibly smooth, if you didn't hear the exhaust you wouldn't even know it is running. It also helps free up a few HP but for me the biggest gain was how smooth it made the motor.

 

What is blueprinting?

 

I knew that was going to be the next question. Frankly, I want to know the same, however, I will venture a very risky guess.

My guess: blueprinting is ensuring that all of the engine specs are the same. For example, the ring gap on cyl. 1 is the same as all the other cylinders. I guess another way to put it is that you define very tight tolerances for all the internals and then make sure when you build that you stay within those tolerances. Furthermore, these tolerances would be much tighter than Nissan spec, and therefore worth doing. But then again, this is only a guess, so please don't flame me.

 

You are pretty much right but also it is recording every measurement so that it can be replicated in the future and when a problem is sensed the cause can be diagnosed and hopefully prevented in the future. It is knowing your motor like the back of your hand so to speak.

 

My definition of Blueprinting is basically returning the motor to the specs that the engineers originally intended but product line could not meet. As far as ring gap, each of the rings should be manually filed to match the cylinder that they are going into.

 

there are a number of good books on the subject- takes time and patience.
Balancing is several items, the biggest is to weight-match all of the moving parts, grind the counterweights on the crank so that it does not know a "heavy spot". In big American engines, they think that 1-2 grams is good enough for most applications.
check the flywheel for off-center weighting- there are usually little weights welded onto the flywheel, or drilled out holes to put the center of mass roughly on the center of the crankshaft
Blueprinting- much tougher problem. Here everything is matched- valve mass, spring rates, cam lift, ring clearances, bearing clearances, spring height, rockers, pistons, valve seats, valve faces, exhaust porting , intake porting, deck flatness and height, head flatness, gasket thickness in compression, etc etc etc.
big job....
But, if you do it yourself, you can learn a lot and save a bunch of green. There are a lot of tools needed- see Summit or JEGs. So, you might end up spending as much on the tools as you save doing it yourself. PLUS- the guys that do this for a living, do not have to learn.... could be more expensive. Main point is keep track of everything, take pictures, write notes, take more pictures, keep everything clean, and you could be successful. You might want an engine hoist, and an engine trolley, too. And enough space to work on it with out having to put things away...

 

Mike the Admin guy,

from my old Chevy Camaro days, balancing and blueprinting used to be the hallmark of a well built Chevy small block V-8 engine (for the reasons mentioned above). Not just Chevy's of course, but all domestic race engines. Of course next was porting and polishing the heads, why did they do it you ask? Well the heads were not smoothly finished due to antiquated manufacturing processes. These days (and especially on the imports) these processes have been refined and there is not as much available HP on tap by using the above techniques.

Why was there so much easy to find horsepower available on old cars? Let's look at a Ford Mustang from 1990. 225HP from a 5.0 liter V-8 (45HP/liter). That right there tells you that Ford had their head up their *** and there was ALOT of spare HP to be tapped. And the Ford Mustang owners will agree with me, THEY FOUND IT!!!

Now take a current day Mustang (still a piece of shlt, but just roll with me on this one) 4.6 liter with 260 HP (56.5HP/liter). The aftermarket tuners can still get good gains, but it is WAY down from the days of the 5 liter. Now let's take the S2000...240HP from 2.0 liters (120HP/liter....this is better than any n/a Porsche that comes to mind) good luck tuning it, there were ALOT of highly paid engineers that designed that car, almost anything you bolt to it will cause a loss in HP (other than FI of course).

Now, our Z isn't that bad, but at 82HP per liter for a V-6, don't expect a ton more power to be available without FI. I wish the power was there to be tapped, but history (and some pissed off 350Z modifiers) tell us otherwise. Even to get the 30rwhp n/a gains that some people have achieved, it has cost them $100 per HP... if you include installation charges, then even a bit more than that.