Balancing Bottom rotating assembley

[fast924S]

Hey guys, Just got my Spec light weight flywheel in the other day, Now that I have everything im gonna send the crank,flywheel,connecting rods and pistons, to the machine shop to get balanced and have #2 and #3 cross drilled and have the rods cleaned up and install the arp rod studs. My question is about the balancing, Besides flywheel, crank, rods and pistons do I need to include the front pully and gears??? Also should I include the pressure plate??? I just want to make sure I send everything I need. Thanx alot guys.

[fast924S]

bump

[nynor]

i think you may be beyond the 'normal' expertise...

that said, it was my understanding that the major components (flywheel and crank) were balanced independently. in other words, the flywheel was balanced by itself, the flywheel was balanced by itself, etc.

[fast924S]

I thought they balanced them independently and then together so they match.

[944 Ecology]

Nope, they balance them only independently, so you don't have any balance aligning marks. If they balanced them together, you would have to ensure that all of the parts lined up exactly every time.

[nynor]

i am not sure that would be necessary. if the crank is balanced and the flywheel is balanced, you put them together and they are balanced.

after all, you can buy a flywheel seperately, which would be nearly impossible, well very difficult and requiring disassembly of the engine, if they had to be balanced together.

its also a fun project to make all the pistons and rods and so on weigh the same.

[Rick V]

Balancing the pressure plate won't hurt, you would be amazed how far they can be. I also have mine balanced when I do them. As for the pulley on the fromt of the engine, that is the balancer, no need.

[fast924S]

New info I found cool.



Balancing is the action of matching weights of the reciprocating parts of the engine. These parts include, but are not limited to:

Pistons and Piston Pins
Piston Rings
Rod Bearings
Connecting Rods (large and small ends)
Crankshaft
Damper (harmonic balancer)
Flywheel/Flex plate
Pressure Plate/Clutch
"Estimated" Weight of oil
Once you have these parts together, the process of Balancing the parts goes as follows:

First, the individual parts are weight matched. These include the pistons, rods and rings. There is not much you can do to the rings or rod bearings so, other than just setting up the "File-Fit" rings before balancing, all you do is supply a "single set for "one" piston" to the shop doing your balancing. You first weigh all the pistons and all the rods, locating the lightest of each. At that point, if you are reducing weight of these items, do it first to the lightest parts. You now match weight of the pistons and rods.

NOTE: "All" other machining must be done BEFORE balancing is attempted...!
The RODS are matched as "small ends" and "big ends". This means you match all the "big ends" by hanging on a special hanging fixture, then you do the same with the small ends. Be sure to double-check!

The PISTONS are also weight-matched, but the "material removal" machining is done either under the piston pin boss with a special offset cutter, or it is done by drilling holes (very carefully) on the surface of the pin boss. You do this to both piston bosses, sharing the material loss. You DO NOT want to remove the material off only one side.

The Damper, Flywheel/Flexplate, Pressure Plate, etc. are individually spin balanced. Just like the wheels and tires on your car.

After you have completed this weight matching, you are now ready to mount the Crankshaft in a special Balancing Machine that spins the Crank with the Damper and Flywheel installed, as well as "Bobweights" that duplicate the compiled weight of the Pistons, Pins, Rods, Rings, Bearings, and a calculated "weight of oil". The crank is usually mounted in Teflon or Nylon "V-Blocks" on the Balancing Machine. The Balancing Machine measures "out-of-balance" through Computer-Controlled sensors. Just like the way your wheels are balanced when you have tires installed (or hopefully during normal maintenance as well), yet the engine balancing machine is much more accurate.

Any errors in the balance of the crank is corrected by either:

Drilling to remove weight
Welding to add weight
Machining and Adding "Heavy Metal" (Mallory Metal)
The Balancing Machine in many cases has a Milling Machine built on to it, making quick removal of material. The Milling occurs on the crank's counterbalances. If metal (weight) needs to be added, it in most cases is done within the existing balance holes in the crank. In other cases directly to surface of counterweights. In only extreme cases, typically with very lightweight design crankshafts, is Mallory Metal used.