Does a new flywheel need balancing?
Thread Starter
Instructor
Joined: May 2004
Posts: 199
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From: Santa Monica CA
Does a new flywheel need balancing?
Hey everyone. I'm putting in a ZZ4 that was previously rebuilt and balanced with a flexplate, which I'm replacing with a GM flywheel... it didn't occur to me that this might throw off the balance of the engine, so will I need to get this thing balanced? Please say no... Thanks.
Dave
Dave
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St. Jude Donor '11, '16-'17
In a perfect world, I believe that the flywheel, clutch, and pressure plate should all be balanced with the rotating assembly. I can't tell you how much it will affect the engine balance by not doing that. I think people mix and match crate motors with flywheels or flexplates fairly often though.
Thread Starter
Instructor
Joined: May 2004
Posts: 199
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From: Santa Monica CA
Thanks fellas, that is EXACTLY what I wanted to hear. 
I'll just put it in and hope for the best... BTW, I'll know it if the rotating assembly is off balance, right? There will be consistent vibrations at specific RPMs?
I'll just put it in and hope for the best... BTW, I'll know it if the rotating assembly is off balance, right? There will be consistent vibrations at specific RPMs?
Burning Brakes
Joined: Aug 2000
Posts: 1,239
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From: NY
I would drop the flywheel off at a machine shop and verify the balance.
MUCH easier now.
The best way is the entire rotating mass balanced as one. You WILL feel the difference and have safer Hi RPM's not to mention longer engine life.
MUCH easier now.
The best way is the entire rotating mass balanced as one. You WILL feel the difference and have safer Hi RPM's not to mention longer engine life.
Race Director
Joined: Nov 2000
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From: Waterloo ontario Canada
If you drop the flex plate along with the flywheel at any balance shop they can match the two. They measure the offset balance of the flexplate and make the flywheel equal that.
Le Mans Master
Joined: Apr 2001
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From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
A 350 is internally balanced so there should be no balancing weights needed on the flywheel or balancer. It is not like a small block 400 which is extenerally balanced.
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Melting Slicks
Joined: Nov 2003
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From: San Antonio TX
I am sorry I am going to jump in here just a tad. I would do like Norvalwilhelm said and take the flywheel along with the pressure plate to a balance shop and have them balanced together which is your best bet from a person that has gone through plenty of clutch plates lol. The Ideal is to take the crank,one rod one piston with pin and retainer and rings and harmonic ballancer in and have the assembly ballanced that is if previously the engine was ballanced if not take everything and have it done. And the choice of the flywheel if not already picked I would probably go with a Steel Hays depending on RPM the engine will see. It has been a few years but I remember that Hays also offered a light flywheel not by much only 5 pounds but it did make it rev a bit quicker.
Race Director
Joined: Nov 2000
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From: Waterloo ontario Canada
Originally Posted by Sigforty
A 350 is internally balanced so there should be no balancing weights needed on the flywheel or balancer. It is not like a small block 400 which is extenerally balanced.
While your flexplate may be neutral balanced and it probably is he can quickly make sure of that and that the flywheel is also nuetral balanced.
At the same time as the flywheel was made equal I also brought the pressure plate and had it checked at the same time.
Once the flywheel was right on the pressure plate was bolted to the flywheel and we made sure it didn't change the balance.
Thread Starter
Instructor
Joined: May 2004
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From: Santa Monica CA
Thanks again everyone. I just took the old flexplate and the new flywheel to the balancer... but I didn't bring the pressure plate because I was slackin' on my forum reading 
Is this equally as important as the flywheel?
Is this equally as important as the flywheel?
Le Mans Master
Joined: Apr 2001
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From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Norval I guess it all depends on how close you want things. I figure it is close enough for government work, but I guess if you are racing or going for a more extreme setup it is worth it.
Team Owner
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From: eville in
Originally Posted by norvalwilhelm
If you drop the flex plate along with the flywheel at any balance shop they can match the two. They measure the offset balance of the flexplate and make the flywheel equal that.
this is the way to be sure 
also take pressure plateto keep all correct
