Checking flywheel balance?

[porschetub]

Anyone checked an early 911 flywheel for balance?,as its going on a 2.2 and was wondering if it might be a good move considering the non-counterweighted crank?
Have followed a lot of engine builds on here and not noticed it being standard practice ,my flywheel isn't worn by the way.
Would consider doing the pressure plate also,thanks

[HawgRyder]

Normally a front pulley/crank/equivilent rod weight/flywheel/pressure plate/clutch disk are balanced together.
In some cases...where the flywheel is simetrical (not off set weighting) you can balance it separately.
Horizontally opposed cranks are inherently IN balance separately...but...depending on how anal you are...best to do the whole assembly at once.
It also depends on the RPM expected.
A 1 gram imbalance might not be too bad at 5000RPM...but the same 1 gram at 9000RPM could shake an engine apart.
It all costs money...and you have to weigh those costs against the overall price of doing the engine...and how long you expect it to last.

[911pcars]

Originally Posted by HawgRyder

Normally a front pulley/crank/equivilent rod weight/flywheel/pressure plate/clutch disk are balanced together.
In some cases...where the flywheel is simetrical (not off set weighting) you can balance it separately.
Horizontally opposed cranks are inherently IN balance separately...but...depending on how anal you are...best to do the whole assembly at once.
It also depends on the RPM expected.
A 1 gram imbalance might not be too bad at 5000RPM...but the same 1 gram at 9000RPM could shake an engine apart.
It all costs money...and you have to weigh those costs against the overall price of doing the engine...and how long you expect it to last.

Several strategies to balance engine pieces. I suggest balancing the pressure plate and clutch disk independently from the other engine parts since they're a wear item that is usually replaced long before the engine is again rebuilt. The flywheel might be in the same category. Not all flywheels weigh the same and refinishing it will affect its weight and its affect on dynamic balance.

In the long run, it's recommended to zero balance these external parts separately from the internal rotating parts.

Maintaining Your Balance: Engine Building Tips to Reduce NVH and Increase Life - Engine Builder Magazine

Sherwood

[porschetub]

Originally Posted by 911pcars

Several strategies to balance engine pieces. I suggest balancing the pressure plate and clutch disk independently from the other engine parts since they're a wear item that is usually replaced long before the engine is again rebuilt. The flywheel might be in the same category. Not all flywheels weigh the same and refinishing it will affect its weight and its affect on dynamic balance.

In the long run, it's recommended to zero balance these external parts separately from the internal rotating parts.

Maintaining Your Balance: Engine Building Tips to Reduce NVH and Increase Life - Engine Builder Magazine

Sherwood

Engine is fully assembled,so as I'am adding these parts to the mix I will be going for the specs suggested cause its no issue,the flywheel has zero wear and the p/plate is NOS german made to me prefered over the ones sold now.

[Walt Fricke]

I'm with Sherwood, but I am pretty sure that flywheels come zero balanced to start with on regular Porsche motors, and from everyone else who makes them. Same with pressure plates.

So no need to balance the two together. Both of these parts usually have shallow drilling holes, which I take to be how the manufacturer got them balanced.

If you are building a cost is no object race motor, and plan to have it apart frequently, maybe balancing assemblies makes sense.

You say this is going on a 2.2. Are you using the 911 transmission? The 2.0 flywheels have the starter ring gear cut into them, and won't work with any transmission other than the 901 (or so I think - smaller clutch disk, and maybe different mainshaft spline count?). The 2.2 and later flywheels have the ring gear as a separate part, and it should also be zero balanced. Though if you have anything balanced, makes some sense (maybe lower cost at the balancing shop?) to balance flywheel, ring gear, and PP as a unit, and have all three parts punch marked and red painted as to how they are to go together.

And if this is strictly a street motor, this may not matter too much. And it isn't coming apart, so you can't do anything about the balance of the internal engine parts.

[porschetub]

Originally Posted by Walt Fricke

I'm with Sherwood, but I am pretty sure that flywheels come zero balanced to start with on regular Porsche motors, and from everyone else who makes them. Same with pressure plates.

So no need to balance the two together. Both of these parts usually have shallow drilling holes, which I take to be how the manufacturer got them balanced.

If you are building a cost is no object race motor, and plan to have it apart frequently, maybe balancing assemblies makes sense.

You say this is going on a 2.2. Are you using the 911 transmission? The 2.0 flywheels have the starter ring gear cut into them, and won't work with any transmission other than the 901 (or so I think - smaller clutch disk, and maybe different mainshaft spline count?). The 2.2 and later flywheels have the ring gear as a separate part, and it should also be zero balanced. Though if you have anything balanced, makes some sense (maybe lower cost at the balancing shop?) to balance flywheel, ring gear, and PP as a unit, and have all three parts punch marked and red painted as to how they are to go together.

And if this is strictly a street motor, this may not matter too much. And it isn't coming apart, so you can't do anything about the balance of the internal engine parts.

Thanks Walt ,p/plate is in transit should be here in a few days,will check for balance drilling,g/box is 914 side shift,flywheel is early 215mm ''pie plate'' type for 914 six swap,car is otherwise fully set up for conversion by the guy I will buy it off.
Haven't checked with my balance guy as it depends on what mandrels he has to do the job ,his specialty/experience will be a good recommendation also,have worked with him for 20yrs off and on...trust him.