[phil400]

Are the factory flywheels neutral balance?

[tom s]

no they are not.Tom

[phil400]

Ok thanks, so when I have my new rotating assembly balanced then I need to buy a new flywheels that is neutral right?

[tom s]

No,just get your neutral balanced.Tom

[phil400]

Alright that's grest news thanks!

[many birds]

Not sure if this pertains to your case since you're getting your rotating assembly balanced. My '75 T/A 400 was externally balanced from the factory . When it came time to replace the flywheel (and clutch and pressure plate), I had to take the new one and the original one back to the machine shop to have the new one match the original one's balance.

[phil400]

I thought they were internally balanced? How were they balanced at the factory?

[Tom Vaught]

Tom S is correct, there is a slight factory in-balance built into the flywheel. This is why you can't bolt the flywheel on in any position, you can only bolt it on one way.

Even after you get the assy neutral balanced, the flywheel will still bolt on only in the factory position.

So to answer your last question.
Many years ago when the Traditional Pontiac Engine was designed, they made a decision to have a slight inbalance in the flywheel.

So it is what it is FROM THE FACTORY.

You can have the flywheel Neutral Balanced separately but it is just as easy to remove both the pressure plate and the Flywheel and rebalance them if the Pressure Plate or flywheel needs to be replaced down the road. The clutch disc is typically not as big of a player on that balance process.

One last comment.

Clutch discs when new have a bonding chemical that holds the clutch material together when it is made.

When the clutch gets hot over time or abused that chemical leeches out onto the surface of the disc. The clutch then "slips" occasionally.

If, instead of replacing the clutch disc, and having the process repeat again, if you have the clutch disc glass beaded it will Remove the glazed over resin, and now the clutch disc will probably last several times longer in the vehicle EVEN being abused. I have followed this process since the 60s and I think I am on my 3rd clutch disc.
I started with the original factory 10.5" disc, later did a second disc, later did the glassbead mod on the second disc (which is still good by the way), and finally went with 11" disc components. No real time on the 11" parts.

Factory balance by GM, then balanced for the good rod/piston assy I installed, and now rebalanced for the latest engine parts.

So I gave you a history, a suggestion, and an example.

Tom V.

["QUICK-SILVER"]

Originally Posted by phil400

I thought they were internally balanced? How were they balanced at the factory?

Factory flywheels/flexplates have an offset weight to compensate for a clearance issue with the rear counter weight. Same amount of weight for all V8's.

Cranks got drilled for final balancing. Not the flywheel/flexplate.

Aftermarket does have neutral balance flywheel/flexplate for high perf engine builds. Trying to use these parts with a factory crank causes problems.

So it's a pick your poison deal on which way you go with it. The factory offset works fine for normal and even moderately high performance street engines. A little different when you get into high hp high rpm engines. High rpm being well past 6,500.

Clay

[phil400]

Great Info, thanks so much. The machine shop I'm using said to balance it, he wants/needs every thing that spins, including harmonic dampner and flywheel or flexplate if it was an automatic.

Is this the same for all GM brand engines?

[phil400]

Ok so what is you guys opinion, have the rotating assembly balanced with the stock flywheel OR have it balanced for use with a neutral balance flywheel?

Sorry for what may seem like silly questions just want to make sure to get this right.

[tom s]

Have the wheel neutral balanced so if necessary it is a easy swap to another neutral balanced wheel.No brainer.Tom

["QUICK-SILVER"]

Originally Posted by tom s

Have the wheel neutral balanced so if necessary it is a easy swap to another neutral balanced wheel.No brainer.Tom

Hey Tom,
Doesn't neutral balance flywheel require adding weight to a factory crank? If so, OP may need to chat with the machine shop before going that route. Lot easier to take away than it is to add.

I don't have a problem with the factory set up. As long as it's not a high rever.
Just don't let the shop add or take away weight from the damper or flywheel, with which ever one you choose. Those need to remain a constant for ease of replacement.

Clay

[Tom Vaught]

Agree the Crank Assy should be bananced with just its parts. The Balancer/Damper should be Neutral Balanced from the Manufacturer but have it checked separate from the Crank stuff or the Flywheel. The Flywheel/flexplate needs to be spun separately from the other two parts wither as a neutral balance or a factory balance.

Key is they all have to be the same.

I use Aluminum Flywheels (aftermarket) and always have it neutral balanced and then again with the pressure plate added as an assembly.

I can't see not going to a neutral balance if any of the parts are intended for high rpm/HP use.

Tom V.

[Doug]

Buy a new and better one like this:

PRW SFI Approved Pontiac Stock (External) Balance 30 Lb. Steel Flywheel- 2.50" or 2.75" Register Bore PRW-1645570

Butler has them for $259. Often cheaper on Amazon.

Universal fit
internal or external balance with removable weight
interchangeable 2.5" or 2.75" register bore with removeable center ring
interchangeable 10.4" or 11" disc
interchangeable pressure plate styles

[phil400]

Ok thanks to all for the info, just to see I went on summit to check flywheel prices, aren't many options for cranks with 2.5" register, I'll check butler's site.

How many times can you safely resurface a factory flywheel?

[lust4speed]

Safety should be addressed at this time. Original flywheel was a big chunk of cast iron and it has led a very long life of heat cycles. Really not that expensive to order out a new steel version, and ordering out a neutral balance solves the balance problem (although I'd still have it checked anyway). When you figure the cost of surfacing the old piece compared to a new flywheel that's ready to bolt on, it's not that bad of deal.

[tom s]

I think the McLeod wheel is the large hole and comes with a ring to use on the smaller.Tom