Flywheel Balance

[Joe Ciaravino]

I am having my 1965 327/365 engine rebuilt, and they will balance the rotating assembly(crank/pistons/rods) during the rebuild. No mention was made of the flywheel by the engine rebuilder.. I have had the wheel surfaced at a local machine shop, where about .030 was removed to make a perfect surface. The '65 shop manual mentions lining up the marks on the flywheel and clutch pressure plate, but I found no such marks. I am installing a new clutch assembly anyway. Does my engine use an internally or externally balanced flywheel, and what is the difference. Must I be concerned about flywheel balance relative to the rotating assembly, and relative to the clutch pressure plate.

Joe

[Mike Goen]

Re: Flywheel Balance

Joe, I'm no expert here, but I just the the rotating mass for the engine I'm building balanced. The machine shop wanted: crank, pistons, rings, rods and one rod bearing set, flywheel, harmonic balancer and the pressure plate. Hope this helps // Mike

[dale pearman]

Re: Flywheel Balance

Look for a new machinist! You are getting stroked if he dosen't want your balancer, flywheel and pressure plate. these components MUST be included as part of the rotating assembly when balancing. Your 327 is internally balanced.

Varooom!

[g.r.rogers]

Re: Flywheel Balance

Joe, Dale and Mike are right on. All my small blocks were internally balanced and only my 454 was external. Case in point, I had my harmonic balancer work loose over a period of time on a 1970 LT1. I ended up breaking the timing chain at 6500 rpm with 456 gears. Cause,"ME" I removed the original heavy flywheel and press/plate/clutch assy.and installed an aluminum flywheel and different clutch/press.plate assy. Thus we figured I had thrown the engine out of balance. I would question the shop that is doing your balancing if they don't include the harmonic balancer,flywheel assy.as Dale and MIke suggest. GRR#33570

[Joe L.]

Re: Flywheel Balance

Joe-----

All Chevrolet V-8s are INTERNALLY balanced except 454 and 502 big blocks and 400 cid small blocks. With an internally balanced engine, the individual componets are balanced seperately and, often, the completed assembly is then checked for balance. At the GM engine plants, the engines are balanced to PRODUCTION tolerances and most SERVICE parts for reciprocating assemblies are also balanced to PRODUCTION tolerances.

Bear in mind that, with respect to a rotating assembly, the term "balanced" is a RELATIVE term. Engines are balanced to a greater precision than, say, bicycles. But, nowhere near as precise as, say, jet engine turbines.

In most cases, the balancing of engine assemblies in SERVICE is designed to produce a "custom balance" which is more precise than the PRODUCTION balance tolerances and to correct any PRODUCTION "mistakes". However, many of the components are still balanced seperately.

All this being said, it remains VERY important to have your flywheel, disc, and pressure plate assembly included in your engine balancing "package". In fact, for smooth operation, particularly at higher RPMs, these components are among the MOST CRITICAL to have balanced.

By the way, the "X" mark on the flywheel is only designed to keep the original PRODUCTION engine balance more-or-less intact when reinstalling or replacing the pressure plate assembly. Your mark may have been removed when the flywheel was surfaced or, your flywheel may have been previously replaced. GM SERVICE flywheels usually don't have such a mark. In any event, the original mark is meaningless once you have the reciprocating components custom balanced.

[Glenn # 32454]

Re: Flywheel Balance

What does this mean when replacing a pressure plate assembly in a normal service situation, ie: worn clutch in an assembled, in service car? Does that need to be balanced too? With what?

http://www.classicar.com

[motorman]

Re: Flywheel Balance

if you balance the flywheel seperate and then balance the pressure plate the next time you balance a new pressure plate they just have to use a balanced flywheel they have at the shop to do your new pressure plate. never balance a flywheel and pressure plate together as a unit.

http://clemz9@hotmail.com

[Joe L.]

Re: Flywheel Balance

Glenn----

I agree with motorman. I'll also add that GM(and other)SERVICE pressure plate assemblies are suppossed to be "neutral-balanced" from the factory. For an internally balanced engine, when you "bolt together" individually "neutral-balanced" components, the resultant assembly should be balanced. However, I have found that factory "neutral-balanced" assemblies/componets are not always "neutral-balanced" to a "precise enough" degree. For a smooth running engine, I recommend having the factory balance checked when installing new pressure plate and/or flywheel assemblies. I've gotten "burned" once on this one with a brand new GM clutch assembly and NEVER AGAIN; I don't like doing things TWICE. If you are just replacing the friction disc/release bearing, you usually don't need to be concerned about balance.