jmcghee

The balancer seperated on my 67 330. Will a W31 balancer be an acceptable replacement? No Im not trying to pass it off as a W31. The 330 was an auto engine that I put in my 64 coupe with a 3 speed. Short on cash. Just want to drive my car. No I dont want to sell the balancer

Magna86

No you need to just order a new stock balancer for the 330.

BangScreech4-4-2

A W-31 balancer on a 330 would be a bit of overkill as it's a rare and expensive part. Advice from @Magna86 above is probably the best way to go.

jmcghee

My 330 has the cam and the heads installed on it. from my 69 W31. When I put the motor together couldnt locate the balacer. I did find some more balancers last night tho. Cleaning out the barn. Finding stuff I havent seen since the 70's . Why did the factory put heavier balancers on the W31? Why cant you put a W31 balancer on another small block? Far as I know a W31 and any other 350 used the same flywheel. Only reaon I can find for the W31 balancer is because the motors were deseiged to rev higher than other 350s My 330 will rev higher than other 330s What value is an unused part?

BangScreech4-4-2

Well, a lot, especially to a W-31 restorer.

OLDSter Ralph

The harmonic balancer is related more to reciprocating weight. I think the pistons from 330 are a different weight than 350. This could explain why a 330 harmonic balancer would be a better choice.

66SportCoupe

Don't waste a rare piece on this engine. Find a more common balancer

bccan

At the risk of coming across like a dick, which I’m not trying to, a W31 balancer might cost as much as your whole engine cost.

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joe_padavano

That's fact, not a criticism.

jmcghee

" The harmonic balancer is related more to reciprocating weight. I think the pistons from 330 are a different weight than 350. This could explain why a 330 harmonic balancer would be a better choice. " Thanks Ralph Finally, This is starting to make sense . i am trying to find out why the factory put heavier balancers on the W31 cars. I know they bring big bucks, dont care. i enjoyed my W31, and saved much as I could. I would like to replicate the performance in my 64 coupe Thats all . When I said was short on cash that was money to send on cars at the monment. If any one has any pertinent MECHANICAL INFO I would appreciate it. Thanks guys

BangScreech4-4-2

I'll just point this out one more time and then shut up: if you sell that balancer and get one that's designed for a 330, the proceeds could finance a lot of work on your car, with no sacrifice in performance

Run to Rund

330s have different counterbalance in the flywheel and damper than 350s do.

jmcghee

So, does that mean the W31 balancer can be put on any 350? Does any one know the technical mechanical reason for a W31 balancer?

jmcghee

So, does that mean the W31 balancer can be put on any 350? Does any one know the technical mechanical reason for a W31 balancer?

OLDSter Ralph

I have never heard the reasoning for the "special" harmonic balancer on the W-31. Oldsmobile engineers may have had a reason for the "special" harmonic balancer.
I would venture a guess that if you ran a 350 on a dyno and only changed the harmonic balancer, you wouldn't see any change in horsepower or torque.

cutlassefi

No they don’t. The amount of IMBALANCE is the same for all Olds 64 and up.

CANADIANOLDS

the technical reasons for it being thicker and heavier is so it can better dampen the harmonics of the whole rotating assembly at higher RPMs

The W31 was designed to RPM much higher than any other Olds engine at the time, they were smart and decided, let’s make sure this thing lives at those RPMs

every damper Olds made was balanced individually to a specific out of balance. The inner hub is part of the counterbalance on the Olds, just like the flywheel…it’s external balanced on BOTH ends

the outer ring of most dampers also have drilled balancing holes to get to the correct counterbalance needed for each engine. You’ll be hard pressed to find any two dampers that are drilled the same , even between two engines that came off the assembly line beside each other

that includes the W31 damper. I’ve had a few pass through my shop and none have been identical from what I’ve seen. Here’s a W31 damper that has two drill holes for balancing. Even if you find another one with two drill holes, there is no guarantee they will be the same counterbalance grams out. That’s because the drill depth could be different and the hub casting could also be different from one to another.

the factory wasn’t that precise on the grams each piece could be out, but it was good enough for assembly line quality.

the damper will physically fit of course. But it will not be perfect for your engine because it never came from it in the first place. Will you notice it being a few grams out? I doubt that.

is the gain in better harmonics dampening worth it over maybe some minor out of balance ? I doubt that too.

these two W31 that came through my shop were balanced different. One had one drill hole, the other had two

jmcghee

Quote Canadianolds "every damper Olds made was balanced individually to a specific out of balance. The inner hub is part of the counterbalance on the Olds, just like the flywheel…it’s external balanced on BOTH ends

VC455

Consider that the damper assembly on an externally-balanced engine performs two functions.

It has to counteract bending forces on the crankshaft, and it must absorb torsional vibrations. Each of the two parts of the damper performs one of those functions.

The inner hub (and flywheel) has specific unbalance to counteract bending forces on the crankshaft. I am told that this hub is the same on each engine family.

The outer hub is an inertia ring to quell torsional vibrations in the crankshaft. And, as such, it must be neutrally balanced so that it does not add or subtract from the job of the inner hub. Being that it is a casting with the usual variability, the drill holes that ensure neutral balance would not be the same from hub to hub.

The outer hub acts on torsional vibrations through the rubber that connects the two parts of the hub assembly.

The larger outer hub of the W31 has more inertia than the usual, smaller outer hub has. Therefore, it would be more effective in damping torsional vibration on the higher-rpm W-31 engine.

jmcghee

thank you VC455

CANADIANOLDS

it’s rare that I need to do anything to a factory damper (never) or flywheel/flexplate (sometimes)….on a stock type build externally balanced build.

Sometimes the flywheel/flex plate does need a touch up only because it’s easier to do if the crank counterweight can’t do it on that end.

here’s an example. I just did a mild low budget 350 using all factory parts…but they are heavier…yet didn’t have to do anything to the stock damper and flexplate

went from 350 to 403 rods…they’re heavier on big and small end.

i went with factory nos 4.125” small dish Toronado pistons from a big dish low comp one..so we gained weight there. It’s easy to trim the 403 rods to stock 350 rod weight on the small end to also take in to account the heavier piston.

then lighten the big end to match the 350 rod..that’s it., done. It’s now the same as it left the factory. Didn’t have to touch the crank, flywheel or damper. Here’s the 403 rod small end lightened and shot peened …before and after

CANADIANOLDS

yep, pretty close. But the hubs are cast , and like you say, they vary because of casting differences. There a few different hubs. The W31 is specific to it because of the width

they are pressed together and then balanced as one piece. That’s when they get drilled to a specific counterbalance/out of balance number .

that’s why no two have the same drill spots for balance