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Topic: BIG BAD Balancing problem HELP PLEASE

badazzcougar
Gearhead

Posts: 132
From: Seattle
Registered: Oct 2001

posted 11-24-2001 12:26 PM

Heres my dilemna .. I have a 1972 vintage 351 cleveland engine. It was rebuilt by a
reputable builder a few years ago . The guy I bought the car from had the work
done . I am in the process of rebuilding the motor at this time to add more
compression, change the cam and heads and generally freshen it up for the spring.
Anyway it appears to have been internally balanced. There is considerable weight
removed from the rods balancing pads and there is quite a bit of weld metal weight
added to the crank counterweights. I made sure to keep the new piston weight the
same as the old but where my problem lays is in that the flex plate is made for an
externally balanced engine. Ever since I bought the car i have had a vibration
problem and when I pulled the motor I noticed that the welds along the outside of
the flexplate starter ring where the balance weight are were cracked. I understand there are
different flexplates for cleveland motors. Do I need a internally balanced flexplate or
do I need the externally balanced ? I dont even want to ask the guy I got it from as
he was a yutz and couldnt mechanic his way out of a wet paper bag and I'm pretty
sure he wouldnt know the difference between internal balance and external balance and I'd bet he installed the wrong flexplate. I want to install this engine back in the car next week but i dont want to pull it again to correct this problem. any help would be appreciated!

[This message has been edited by badazzcougar (edited 11-24-2001).]

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Moneymaker
Administrator

Posts: 25883
From: Lyons, IL, USA
Registered: May 99

posted 11-24-2001 01:25 PM

I'll try to help you out. An internally balanced engine is a zero balance reciprocating assembly. The flywheel/flexplate and balancer will have no weights.
Just because you have material removed from your parts does not indicate that you have an internally balanced engine. All balance jobs will have to have the crank balanced from front to rear and the piston and rod assemblys will all have to weight the same. Most engine builders will have to hang weight on the flywheels and remove some off of the balancer.
I would suggest bringing your crank, pistons and rods, rings and bearings, balancer, and a new flex plate to a reputable machine shop and have it all spun. Especially since you have always had a prior vibration.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
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