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Discussion Starter · #1 ·
:confused0006:When you balance a rotating assembly,Should you include the pully assembly that you are planning on using?
 

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I guess because it is run by belts so doesn't affect the rotating assemblies in and on the motor.I have never really given it much thought. I believe that the makers of each component balance them individually, i.e. alternator,a/c compressor.
 

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Discussion Starter · #5 · (Edited)
I guess because it is run by belts so doesn't affect the rotating assemblies in and on the motor.I have never really given it much thought. I believe that the makers of each component balance them individually, i.e. alternator,a/c compressor.
That is what i thought, but i was in the garage and i was looking around the motor on the stand, and this question came to me,Why isn't the pulley assembly considered part of the rotating assembly?The flexplate or flywheel is. So why not the pulley assembly?
 

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Not sure about the pulley maybe ask you machine shop personnel. If running a flywheel, I would also include the pressure plate. The machine shop I used recommended including the pressure plate as part of the rotating assembly because of the mass of the pressure plate. When I got the parts back, the pressure plate was marked to the flywheel so when I took it apart for assembly, I could reassemble in a "balanced" configuration. Good luck.

Bob
 

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pullies are round, light, and of little significance weight wise when balancing an engine, not to mention they are dampened by the belts.
 

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My understanding is that reciprocating mass needs balancing, where the crank and pistons go back and forth, the balancer has offset weight, and the flywheel is heavy and large enough diameter that a small weight imbalance becomes reciprocating mass (or it has its own counterweight). Some cast iron pullies are also balanced, probably because the weight and inconsistency of cast iron could result in a heavier side going back and forth.
A stamped steel or spun aluminum pulley would have to be pretty badly made to effectively have any reciprocating mass, although technology in China is making some progress in that area.
 
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Kinda makes a little sense which kinda :bowtier:scares me. Lloyd :bowtier:

My understanding is that reciprocating mass needs balancing, where the crank and pistons go back and forth, the balancer has offset weight, and the flywheel is heavy and large enough diameter that a small weight imbalance becomes reciprocating mass (or it has its own counterweight). Some cast iron pullies are also balanced, probably because the weight and inconsistency of cast iron could result in a heavier side going back and forth.
A stamped steel or spun aluminum pulley would have to be pretty badly made to effectively have any reciprocating mass, although technology in China is making some progress in that area.
 

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"We" balance pressure plate and flywheel to zero as indvidual components...that way you don't mess the engine balance if you need to change them later on. Its wise to balance new components aswell like flywheels. What come to pullies I have seen some factory stuff balanced, ford for example balance high perf engine pullies, if I recall right even Buick and Caddy stuff are balanced.
I'm using very light aluminium machined pullies so I thought that they must be in balance but the factory pullies are heavy iron and manufactured differently so its good idea to balance them to 'zero' IMO.
 

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As a point of clarification, the machine shop I used balanced the rotating assembly as a whole unit, without the pulleys. Prior to the work being done, we had a discussion about balancing flywheels and clutch pressure plates. Although the machine shop asked for these items so they could be balanced separately from the rotating mass. Being balanced separately allows the end user to change flywheels and clutch pressure plates with out affecting the rotating mass. The flywheel was balanced first and then the pressure plate was balanced to the flywheel. Seems to work just fine. Sorry for any confusion in my previous post.

Bob
 

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pullies are round, light, and of little significance weight wise when balancing an engine, not to mention they are dampened by the belts.
The first part is correct. Note the heavy cast pulleys, like some 60's BBC crank pulleys are factory balanced. The latter part about belt damping is pure fantasy.
 

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Kinda makes a little sense which kinda :bowtier:scares me. Lloyd :bowtier:
If you mean China's tech advancements in manufacturing apathy (like tilt columns that disconnect the steering), that kinda scares me too.
If you mean my post sounding generally sensible, I get that sometimes; friends get worried when I start making sense.

Shopping for a BBC water pump, it seemed like there were about five different castings coming out of China, sold under 15 or 20 different US brands, with prices ranging from $50-$125 for different brands of the same pump.
I finally broke down and bought a USA Edelbrock pump.
Back on topic, USA (SWP) pulleys seemed to be used vintage collectible Corvette overpriced specialty items, so I bought some import chrome steel pullies from a reputable seller. The water pump pulley wobbles enough that it hits the pump once each rotation.
If it were round with parallel faces (not laughing), it would probably be reasonably well balanced. So from that perspective, if a pulley (excluding cast iron crank pullies) is imbalanced enough to impact engine balance, it should probably go in the trash.
 

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Discussion Starter · #15 ·
My understanding is that reciprocating mass needs balancing, where the crank and pistons go back and forth, the balancer has offset weight, and the flywheel is heavy and large enough diameter that a small weight imbalance becomes reciprocating mass (or it has its own counterweight). Some cast iron pullies are also balanced, probably because the weight and inconsistency of cast iron could result in a heavier side going back and forth.
A stamped steel or spun aluminum pulley would have to be pretty badly made to effectively have any reciprocating mass, although technology in China is making some progress in that area.
Thanks for that.It makes sense now.
 
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