V8 Vibration at aprox 3000 rpm

390 & up cid Monster Motors
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Posts: 25
Joined: Thu Jan 23, 2020 8:04 pm
Location: Wisconsin

V8 Vibration at aprox 3000 rpm

Post by McComet1963 »

I am pretty sure I have an imbalance issue with my crank and flywheel. Would like your opinion....
Rocks the dash and body around 3000 rpm and up.
Assuming all ok I bought and installed new 50oz flywheel and harmonic balancer.

Built the engine with my son in 2005 and drove few years, then kept till this year.

Originally the builder used Bob Weights of 1581 grams in 2005, I assume he balanced the original fly wheel to match.
I tossed the original flywheel so reference is gone for flywheel.

Removing the oil pan the same original Eagle crank was balanced at the factory with 1481 grams.
I believe this was a stock balance.

So... the question is will 100grams (3.5274oz) difference between a new stock 50oz flywheel and old engine balanced slightly different?
Difference is 100grams / 3.527oz

I not able to find anything on the web about a slight imbalance, only 0, 28 and 50oz.

Questions, comments and concerns...

Posts: 586
Joined: Mon Aug 27, 2007 1:54 pm
Location: maryland

Re: V8 Vibration at aprox 3000 rpm

Post by barrys65cyclone »

best to balance crank, harmonic balancer and flywheel together

Joe Travers
Posts: 1055
Joined: Mon Sep 21, 2020 5:23 pm
Location: Louisiana

Re: V8 Vibration at aprox 3000 rpm

Post by Joe Travers »

Question here-
Is the vibration present running through the gears or is it in final drive only?
Differentiating engine speed & vehicle speed, here. If it's vehicle speed, check tire condition and balance.
I ran into this problem shaking down my car @ highway speeds early this year. Good tread on all tires but found cracking under close inspection on the rear. The PO deflated the rear tires to 12lbs. psi for traction. Bad move on a radial tire :?


1963 1/2 Custom Hardtop

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