I'm in the process of a 355 buildup and have replaced the stock rotating assembly w/ different rods and trw flatops, along with having the crank turned. I'm on a buget building this motor and was considering getting it balanced. I was looking for some opinions, since this my first engine buldup. What are some of the benifits of having it balanced or is it a necessity for long bearing life?

-Thanks Joe

 

Consider the factory doesn't balance engines, but uses parts as spec...they last quite a long time...

That said, the better the balance, the more "free" HP can be had...depends on your budget and engine you're building.

Spend the extra bucks for balancing a 200 hp engine? Probably not, spend the extra bucks for something with more potential...probably so.

 

Its always good to ballance and engine esecially when using stock components with aftermarket ones. Since your using another rotating assembly you might want to consider ballancing it. If you go all aftermarket, rods, pistons, ect.. then usually theres no need. It just depends, would you deam it nessasary?? Like Mike said it may show an improvment or not. If I was on a tight budget with a mild 355 I probably wouldent do it.


SSC

 

Thanks guys, My motor probably won't spend too much time in the upper rpms, so I think I'll just weight match everything and be done with it.

 

nevermind. It seems like everything I say involves DIY.

 

Just think of it thisway, if it is unbalanced, the motor has to expend energy fighting that imbalance. Rather than wanting to rotate around the center of mass, it will want to move the crank in a circle around the outaside of the bearings. Not oly do you lose power, you gain vibrations. If you can swing the balancing, I'd do it! Hell, I'd go a week extra w/o my car if it meant I could have the motor balanced while I was building up the motor! Remember, to do it later will involve another engine rebuild! It *will* respond to balanceing, how much depends on how out of balance the parts are, but there is an immediate gain, usually5-25 HP from what I have heard, just because the motor isn't fighting itself.
Corry

 

What's it cost to get it balanced?

 

I think its definately worth it- you'll have a much smoother better runnig motor. Its not that expensive to do....

 

I believe that the factory balances crankshafts.

If they don't have to add molly metal, it should cost about $150. That would include rod mass equalization, piston mass equalization, and crankshaft balancing.

 

It all depends. It should just be labor, no parts involved.

My last build 355 for the bird cost $140 to ballance. A few years back when I was building the 355 for the camaro it ran $160 and they really took some meat off the bottem of the rods and also drilled a small hole on No.3 piston. KB's are ballanced from the factory my butt!!

SSC

 

If the pistons and rods are close to the same weight as your originals balancing isn't required. If you weigh the stock pistons and rods, you will see there is a difference[in grams]but all are within tolerance,of course the closer the match from stock to aftermarket the better.

 

Thanks,
I'll have to do some more looking around. The one machine shop I asked wanted $250 to balance it, but this is a VERY reputatable shop that builds only hi-pro race motors. I am putting TRW's, different rods and had the crank turned .010 over, so I'm sure it couldn't hurt anything
and I wont be kicking my self in the *** later.

 

If you can find a crankshaft specialist, that's the way to go.
Not only is it cheaper then a all in one machine shop, they have better equipment.

In fact, I don't even bother with having my crank ground, instead I just extange it with those guys. (unless it's a $1200 dollar steel nitrate treated bad boy)

Those TRW's are heavvvvyyy, and the counter wieghts on the crank are not going to be equal vs stock pistons.

Think of it as taping a couple of quarter to one blade of a ceiling fan. You'll notice the wobble even at lower RPM.
Everything suffers from an inbalance. (bearings, front/rear main oil seals, thrust bearing on your clutch, etc...)

Ron