Balancing
the Pressure Plate
With the rotating assembly
balanced, an additional step that ensures an extremely smooth
running engine is to include the pressure plate as part of
the balancing process. Since one is likely to change a pressure
plate during the life of the engine however, the balancing
process is done separately from what we just covered.
Not part of the normal pressure plate balancing process
but worth mentioning. Our Centerforce flywheel was drilled
and tapped to accept the Hays 11" Long Style pressure
plate. |
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The flywheel and pressure plate are bolted to the crankshaft
and the Hines balancer is prepared to be spun to 500 RPMs
once again. |
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The weight of the pressure
plate on the rear of the crank has an extremely slight
but measurable effect on the front of the crank. The "OK"
reading for the front of the crank is within spec but
not equal to the value achieved during the balancing process
prior to adding the pressure plate.
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Since we're concentrating on the pressure plate, which
is on the rear of the crankshaft of course, the only reading
to be concerned with here is the 28 grams of material
to be added at 29 degrees. A factory balancing slug is
removed from the pressure plate. |
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Next, a slug is added near or around angle 29 on the pressure
plate. |
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Since there are only a handful of areas to add slugs on
a pressure plate, the slug we added causes the Hines balancer
to now suggest removing material. This is a desirable
consequence because with a die grinder, material can be
removed from an infinite number of locations on
the perimeter of the pressure plate's stamping. |
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With the pressure plate balanced, it is punched for indexing
during reassembly. Rotating assembly balancing for our
400 is now complete.  |
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Posted by sobill, 04/16/08 11:36am:
A great article. Details we would not normally see. This is why I subscribe.
SOBill
Posted by 347LX, 04/17/08 07:15pm:
awsome ,keep up the good work, this is what I like to see!
Posted by job1bf, 04/18/08 07:09am:
Just curious, by comparison what the bob weights of some of the other popular combos 302, 347, 351, 408, etc? I assume lighter is better? Can it be too light for street use?
Posted by zaneabel, 04/21/08 02:32am:
Great Tech article for an Externally Balanced engine.
Would really Like to see some informed info on an Internally balanced engine.
Say a 351C. Top stuff fellas.
Posted by Samickguy15, 04/21/08 07:06am:
Very nice! Anybody know what a ballpark estimate is on price? Or maybe previous experiences?
Posted by 69mach1guy, 04/21/08 08:41am:
Great "magazine"! I look forward to each issue. Always something to learn. You've taken an old shadetree mechanic and taught him there is info and technique beyond "what always works" and "other mechanics opinions". The Web is a great place to do research, but you need to be careful of not taking everything as the truth. I've scoured every page of your website and have enjoyed it and learned a lot. When talking to machine shops or repair shops, I can sound reasonably intellingent. Thanks, Doug Erickson
Posted by lx347cid, 04/24/08 07:03pm:
so when I buy a zero balanced rotating assembly do I still need to get it balanced with my flywheel and balencer at my own machine shop?
Posted by LeadsledCoupe, 04/25/08 05:07pm:
It would have been interesting to see engine dyno data on two identical engines, one balanced, the other not. There seems little new here unless new folks need refreshers on what a balanced assy actually is.
I look forward to other new articles.
Posted by basketcase, 09/03/09 10:06am:
What about Torque Converters? Should they be ballanced as well?
Posted by wherewasi, 09/22/09 11:32am:
In the reciprocating weight calculation... how come the total wasn't multiplied by 2 (for the number of pistons/rods? (Like it was for the rotating weight)
Great article... thanks, Tom
Posted by bobsstocker, 09/14/11 09:18am:
You can see how important balancing is. Make sure when you have your engine balanced the tech and you are on the same page. Bring him all the parts to be balanced.One last comment, Don't balance an assembly that's going to be spinning at 7,000 to 8,000 RPM and you will see why it's so critical to engine performance. (Try to save money here will only wind up costing you more ).Some guys suggest a 1% overbalance. That's your call if you are changing rotating parts in the field right out of the box. Like some top fueler's do.
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