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CorvetteforumC3
CorvettesBalancing
a flywheel on the car

norvalwilhelm
Senior
Member

1900
posts [100%]
Waterloo ontario Canada

Balancing a
flywheel on the car

10:55
AM 7/24/2002

I started with a balanced engine and flex
plate. I later switched to a flywheel which I had balanced by
the original shop. They checked the flex plate then match the
flywheel to it. After installing the flywheel I noticed that
at 2700 rpm and again at 3500 the motor shuttered slightly
passing through these rpms.
I bugged me so having nothing
better to do I removed the flywheel cover and left it off. I
removed the oil filter. I then divided the flywheel in
quarters or every 90 degrees. I did this by marking a tooth,
counting out 42 teeth, this is a 168 tooth flywheel, and
marking it with magic marker to make sure all holes would come
out in good locations. I then did it accurately a second time
using a punch and marking exact locations of holes every 42
teeth 5/8th of an inch in from the ring gear. I then carefully
drilled and tapped 1/4 inch threaded holes in these 4
locations.
I then made a 1 ounce weight from a piece of
brass 3/4 inch diameter about 1/4 inch thick with a hole drill
for the 1/4 inch bolt plus a counter sunk head. I weighted
this on a postage scale I have.
I also numbered the holes 1
to 4 by stamping the flywheel. I then reistalled the oil
filter and it is easy to get at the holes from the starter
side to install weights.
I then bolted the 1 ounce weight
to hole # 1. I got in the car, started it up, place my
forehead on the steering wheel then slowly brought the rpm up
watching the tac. The shutter running through the motor
changed its rpm. On my 2nd attempt I just moved it to hole #2
and repeated the proceedure. I felt absolutely nothing to the
test rpm of 4600.
I have driven the car for a week like
this and often run it up to 4500 slowly trying to feel
anything. Smooth as anything.
I will sometime move the
weight to 3 and 4 locations to check it out but for now hole
#2 smoothed out this slight shutter.
When I have nothing
better to do I will also make different weights and try them
in hole #2 and see if this is better.
This does not replace
balancing an engine. Mine was balanced extremely carefully but
when I changed flywheels it was not perfect. This just allowed
me to fine tune without pulling the entire motor apart and
redoing.
For those with a slight shutter someplace and
nothing to do for an afternoon this could solve that anoying
tremmer.
Just thought I would run this past you so maybe
someone else could try it if all else fails before tearing
into the motor.
Have a nice
day

_______

Norval

burners
Senior
Member

1604
posts [100%]
Santo, TX, USA

Re: Balancing a
flywheel on the car (norvalwilhelm)

11:24
AM 7/24/2002

Not bad, I'm impressed. That's a huge time
saver when compared to rebalancing the entire engine. You
should put this is the tech tips
section.
_______

1978 L-82 4 spd
Steeroids rack
& pinion conversion
Spherical rod end clutch linkage

MasterDave
Moderator

1920 posts [100%]
Tacoma, Wa. USA

Re: Balancing a
flywheel on the car (norvalwilhelm)

12:03
PM 7/24/2002

Hehe, that's pretty good but if it's a 327/350
the flywheel is neutral balanced as opposed to the externally
balanced 383/400 engines. I suppose the clutch/pressure plate
could have been out and you fixed it by this method. If you
replace the clutch it may be off again. When I was a punk kid
I put a big '57 Olds V8 and auto tranny in my old '53
Studebaker pickup. I had to cut & weld the drive-line. It
was WAAY out of balance, to the point of blurring your vision
and seeing as I only had abut $4 to my name in those days, I
just jacked up the rear end, opened the door, put it in gear
and set the rpm's at like 2000. The door vibrated so much you
couldn't see out the side mirror. I got under and let the drive line hit a
piece of chalk, shut it off and hose clamped wheel weights on
the opposite side of the chalk marks. Took about a half hour,
about a pound and a half of lead and the door was butter
smooth. The truck drove great. The only problem was when a clamp worked
its way loose and tossed a couple of weights off. Sounded like a bomb went off inside the
cab when a couple 3 or 4 oz wheel weights would hit the fuel
tank at light speed and then the truck would darn near jump
off the ground 'til I got it slowed down.......I got used to
it but it sure would scare the bu-jeebus outta the hapless
passenger or two. Gawd I loved the 60's!!!
_______

'64 vert
'79 350 (L-82), XE274H, 650 DP, Stealth intake,
Sportsman II (64cc) @ 10:1 CR. Alum roller rockers, 100 shot,
Muncy CR M21...3:70 posi, Power windows
Side Pipes (capped)
2.5" DynoMax turbos.

norvalwilhelm
Senior
Member

1900
posts [100%]
Waterloo ontario Canada

Re: Balancing a
flywheel on the car (MasterDave)

7:21
AM 7/25/2002

It doesn't matter if it's neutral balanced or
not this is just trying to take that shutter out of it. And
yes my pressure plate was checked before installation just to
be sure. I replace a flexplate with the flywheel and
suppositly they were of equal balance. The pressure plate what
bolted to the flywheel as a final check to make sure it didn't
through the balance off.
Alot of balance machines don't
spin high enough to make the harmonic balance work with the
fluid balancers.
This method of sticking a small weight as
trial and error is just to try to make everything
perfect.
I tried to get my driveshaft balance and they can
not go past 3500rpm and yet when the engine is running at 4000
or 5000 in overdrive at .68 I am well above that. Here again a
slight tremor runs through the car that I want to get rid
of.
_______

Norval

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