View Full Version : what is meant by balancing the motor

02-21-2007, 09:07 PM
Does a 289 stude motor need to be balanced? How does it help?

Studebakers forever!

02-21-2007, 09:36 PM
If all the moving parts on an engine are balanced, the engine is a lot happier when it is running. Obviously it doesn't 'need' to be done, because the factory didn't do it. Engines will run a long time without it. Some engines run better and smoother than others, having one balanced increases the chances that your engine will one of the smooth long lasting ones.

Tim K.
'64 R2 GT Hawk

02-21-2007, 10:21 PM
Greetings, studelover,

Sorry, Tim K, the Studebaker factory and all engine factories with which I am familiar balance every engine. Look at the big and small ends of the connecting rods. Some will have all of the square pad on each end and the forging marks still there. Some will be ground down to half the size of others.

Packard, while the owner of Studebaker, static and dynamic balanced all the parts of their V8 and then ran the engine, checked it for balance and rebalanced if necessary to get the ultimate smoothness.

Static balancing - all the pistons and pins are weighed and if there is any difference, weight is removed to make them all weigh the same as the lightest. Rod small ends are all equalized and then the big ends are all equalized.

Dynamic balance - a formula to calculate a portion of the reciprocating weight (pistons, rings, pins and rod small end) and all of the rotating weight (rod big end, bearings and crankshaft) is used to determine a bob weight bolted to the crank pins. The assembly is spun and any imbalance is corrected by drilling out weight from the crankshaft counterweights or adding weight by welding up holes.

This procedure is a must for a performance engine.

thnx, jv.


02-21-2007, 10:57 PM
Thanks for the correction, jv. Now that I think of it, I've seen those drill marks, etc. I had an engine rebuilt and the machinist did all the balancing. So this is something that should be done whenever new parts are used in the engine?

Tim K.
'64 R2 GT Hawk

02-22-2007, 03:15 AM
Tim; this is something that should be done for long term dependability whenever boring the engine and replacing pistons or anything that will significantly change the weights of the rotating parts. Or for high revving performance engines as Packard V8 has said.

quote:Originally posted by GTtim

So this is something that should be done whenever new parts are used in the engine?
Tim K.

Studebakers Northwest
Ferndale, WA

02-22-2007, 08:58 AM
"How it helps" is indeed a good question.
It helps by making the engine run smoother, with less vibration, which means longer component life, and a more satisfied customer/driver. A happy engine will last longer;).

As well as all the comments here, you can do most of the balancing work yourself, at home, and fairly inexpensively.
The term 'balancing' and 'blueprinting' are sometimes overlooked outside the racing engine world.

A simple explanation of 'blueprinting' is to have every machined component match the factory (or race) specification 'exactly', and not just to a 'plus or minus' tolerance. Remember a production item is designed to go through production easily and survive until the warranty period expires. Anything past that is gravy, pride, and reputation.

The term 'balancing; is used to describe the weight of the rotating components and the relationship to the mass of the counterweighted crankshaft throws. This means that there will be less vibration of the rotating assemble (outside of power pulses). Static balance is just the weight of the components. Getting this to match is the first half of the equation. Dynamic balance is the rotating balance of the assembly. You can't do the dynamic balance until you do the static balance.

When a shop 'balances' an engine, they first take all the rotating components and weight them item by item. When they take the pistons, they weigh them all and then reduce the weight of the seven that are heavier than the lightest one. This is usually done by drilling under the piston head near the wrist pin boss, but can also be done by machining under the head, and even turning the inside on a lathe.
Then they do the connecting rods.

There are two methods to rod balancing, and both of them have some neat home methods...
The first (and the fanciest) is to weight the rods at each end using a scale and a jig. The digital scales are a whole lot cheaper than they used to be, and building the jig part is fairly simple (see pic)
This web site http://www.angelfire.com/ca4/CorvAIRCRAFT/RodBalance.html does a real good job describing the process, but basically you want all the big ends to match and all the small ends to match (so you start with the lightest one and grind the heavier ones to match).
The other method is so simple it makes me smile...
Here's a balancer gizmo you can buy for $68.95

Basically you bolt the rods together and grind the end(s) until they balance. You could probably build this jig easy enough. But with this setup you have to be careful to choose the lightest rod to start with. It's a little harder to figure out the rod to rod total weight without a lot of putting them into, and taking them out of the jig.
Once you have ALL your components separated and weighing all the same, then you can take your crankshaft to the balance shop and they can balance your crank to the weight of your piston/rod/ring/wrist pin/cinch bolt/rod bolt/nut assembly (and he only needs to weigh one, as you have done the rest at home. Saves his time to do all the prep work. That will save you bucks. Sometimes they will also want your flywheel and harmonic balancer.
Hope the info helps.

quote:Originally posted by studelover

Does a 289 stude motor need to be balanced? How does it help?

Studebakers forever!

DEEPNHOCK at Gmail.com
Brooklet, Georgia
'37 Coupe Express (never ending project)
'37 Coupe Ex

02-22-2007, 10:31 AM
The "icing on the cake" would be to ensure all combustion chambers are the same size.

John Kirchhoff
02-22-2007, 10:34 AM
Now I know this is rather miniscule, but a well balanced engine is more effecient at producing power than one poorly balanced. This is because it takes power to shake something and that power has to come from somewhere. To put it on a more personal level, imagine yourself with a pipe 20 feet long and a 10 pound weight on each end. You stand in the middle and start turning around in circles. It will take some effort to get the mass moving initially, but after you're up to speed it won't require much effort to keep things moving. Then imagine yourself with a pipe 10 feet long with the same 10 pound weight but you grasping the pipe at the end. Spin around at the same speed and although it will take less effort to get the mass moving, as you rotate you will continually have to expend energy leaning back to counter the rotating mass. Try doing each of the above for 5 minutes and you'll find the balanced one is less exhausting. Yeah I know that's probably overkill, but I find that kind of stuff interesting. I guess I really need to get a life....

02-22-2007, 10:39 AM
I wouldn't call it overkill. Out-of-balance things wear out sooner. Pretty good reason to have the best possible balance in my book.

02-22-2007, 06:14 PM
sounds like a lot of work, I have ok'ed it to be done. I am glad I asked the question. I use to hear people say that " their engine was blueprinted and balanced. I thought they were just talking circles others had their engine "bored and stroked. I know what that means it's just that now they call that a stroker motor. I want my recipricating mass to be balanced and I certainly want the chambers to correct, thanks:D

Studebakers forever!