Moparts Tech Archive
From: sunrise,fla,united states
Registered: Jan 2002
posted 05-28-2002 02:25 PM
i am building a 6-pack motor have block,crank,pistons and rods aloso have correct damper. wanted to get it balanced but was told need a special flywheel. can any one help me with this problem. is there a special flywheel and if so where do i find one thanks chris
is this a 70 and up motor with the heavy rods? If yes, there was a special flywheel, but, it was the same cast# flywheel used on every other v-8 cars but was specially balanced for the heavy rod engines. Since you're building a new motor, I would think you could supply any flywheel in the correct diameter and have it balanced along with the rest of your reciprocating assembly.
i don't think you will easily find an external balance aftermarket fywheel , what you will have to do is by an neutral balnce and have it offset balanced .
i talked to my machinist about this recently and he showed me basicly what is happening the the flywheel with external balance vs internal and its a wonder the external doesn't come apart , the axis of balance rotation goes thru the cranks at an angle vs the centerline of the crank and on the external balnce its way off axis , 2 different ends wit hthe balance axis going in 2 different directions .
also if you internal balance and have to change a flywheel or dampner down the road its a piece of cake swap . not so with the external balance .
thats my 2.5 cents ...
i won't even giving my thoughts on the boat anchor of a bobweight you have with stock 6pk rods and stock type pistons
there's nothing wrong with the stock setup?just be advised that an internal balance is the best insurance for the longevity of your investment,weather it be stock or a $10K assembly.i have ran stock LY 'peened and polished,bushed pins and trw,forged slugs for years and they aren't the modern choice of many but work well,don't worry about the bobweight,unless you are running an NHRA motor on the street or you have alot of money to spend,spend your money wisely and prep your 6 pack rods properly(re-size,polish for stress risers and good bolts)some claim it is cheaper to buy aftermarket than to work the old ones,but for street use 'ma mopar knew what she was doing with rod's!! and they will run well with a nice balance job,
I have a '71 440 which retains the heavy rods, but is internally balanced. This seems a better way to go than external balancing. All I did was go with the Keith Black HyperU pistons which was enough of a weight savings to allow internal balancing. My transmission is an automatic, but I don't know why you couldn't use a standard flywheel and dampner and go with the highly recommended internal balance, whether you use sixpack rods or standard.
TTT , fast , the 6pk rod was a poor bandaid on mopars thought , why they went to a hemi size rod but used the LY size rod bolt is still one for stupidity in cost cutting ...
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