Anyone have their motor fully balanced?

I was wondering if anyone has ever had their motor fully balanced, and if so what kind of numbers they get from it? I know that a fully balanced viper motor can put out about 700-750wrhp, with a stock 450hp motor. so it would be interesting to see what a ls1 or lt1 could do.

Fully balanced. 5 slugs of mallory but it was done.

so, what exactly is "fully balanced"?

Originally posted by SLPSSLS1
I was wondering if anyone has ever had their motor fully balanced, and if so what kind of numbers they get from it? I know that a fully balanced viper motor can put out about 700-750wrhp, with a stock 450hp motor. so it would be interesting to see what a ls1 or lt1 could do.


It's not the "balancing" of the rotating components that increased that Viper from 450 to 750 hp, it's extensive engine modifications. Perhaps you meant something else?

Balancing a motor makes it run smoother, which will give a small gain in HP and hopefully extend the life of the motor. It is also a good idea to shim the valve springs to correct installed height (and always check them for correct pressure at installed height).

Best Regards,

Daren

Most engines come frome the factory with at least 50 percent balancing, when you have an engine balanced at a machine shop they can get close to 0 but that would be pretty rare.

Zero gram balancing is not that rare. The crank guy or machine shop just needs a $25K balancer to pull that off.

Bret

mines pretty damn close i can tell you that. im looking at 430+rwhp when i get all the bugs worked out

Originally posted by Perry93TransAm
Most engines come frome the factory with at least 50 percent balancing, when you have an engine balanced at a machine shop they can get close to 0 but that would be pretty rare.

I don't under "50 percent balancing" in this context. Do you mean 50% of the reciprocating weight rather than overbalance of say 52%? Or did you mean at least 50% of the engines from the factory are balanced? :)

Balancing involves static balancing, that is making all the parts like pistons, rods, etc. weigh the same within a gram or 2 or whatever you care to pay for.

Dynamically, the spinning crank is balanced with "bob weights" attached to the throws. This weight is a calculated amount, generally 100% of the rotating weight (big end of the rod, rod bearings) and 50% of the reciprocating weight (small end of the rod, piston, pin, locks, rings and a small amount of oil). For some applications, the 50% figure may be 48%, 52% or whatever the builder thinks is best for the rpm range used.

The size of bobweight is only an approximation, but engine builders try to get the crank/bobweight assembly dynamically balanced as closely as possible when they spin balance. Dynamic unbalance is quoted in "gm-cm" or "oz-in" units, because it's a torque.

In OEM production engines, the individual part weights are controlled by the manufacturing process. They are machined to size and/or weight tolerances. Rods were the most difficult, especially forged rods. With today's PM rods, there are rarely any balance pads because the parts are so uniform. The dynamic balancing is often done with the short block assembled on a very expensive machine. If ring drag effects "balance", which is another topic, balancing the spinning short block perhaps takes this into account either better or worse than "bob-weights"

My $.02

I meant the 50 percent on the balance, The factory balnces all engines to a point they just dont do it to the point that a machine shop would. Youre right the big machines can acheive 0 balance on an assembly but locally here there are only 2 that I know of (in the state of Ok) .I balanced my rods and pistons before I sent it off to the machine shop and saved myself a few dollors. The machine shop I used has the Sunnen machine and it does a really good job.