428 cj balance

[gdaddy01]

can a 428cj be balanced without taking completely apart? something like cranking it on an engine stand and strobe lighting the flywheel? I had built the engine years ago , but did not have it balanced , replaced the cast piston with forged seal power . I now have a slight vibration now , I don't want to wipe out the bearings .

[Rory428]

Not sure I understand what you are asking, but an engine is not like a tire, there are many moving parts inside, Pistons need to be weight matched, same with the connecting rods, there is no way to properly balance an engine without taking it apart.  The crankshaft needs to be spun up with bobweights, and the flywheel/flexplate is part of the 428s external balancing. Sounds like there is a fairly substantial weight difference with your new pistons. Sorry, but it should be taken apart and balanced properly.

[GerryP]

Crankshafts are balanced by measuring vibration.  It has to come apart to do that.

[pbf777]

can a 428cj be balanced without taking completely apart?

     No!   

     Not in this marketplace anyway.   

     Scott.

[shady]

Did you only change the pistons and nothing else? Is the vibration there in neutral or going down the road? At all RPMs?

[fe468stroker]

Are you sure that you are using the correct flywheel?  The 428 is external balance and needs the specific flywheel/flexplate.  I bought '69 "Q" code Mach 1 that the previous owner trashed the clutch and replaced the flywheel with a 390 flywheel.  The engine definitely had a vibration but not as bad as you would think.  Replaced the flywheel with the correct weighted 428 and cured the problem.

[gdaddy01]

Not 100% sure of anything now days, but I thought I was putting the right flywheel on, it is an aluminum one with the offset balance holes drilled in it. I fell into the trap of reading a well know chevy guy talking about the oil falling on the crank and not needing balancing if you had all the right components in the engine. live and learn, get your back sore. I should have known better.

[machoneman]

Think you'll find the right wheel here: http://www.mustangtek.com/flywheel/Flywheel.html

http://www.mustangtek.com/flywheel/C9ZE-A.html

[Posi67]

The "offset balance holes" on your Aluminum flywheel are probably to zero the wheel and have noting to do with engine balance. As mentioned, 428's need weight added to the flywheel in a specific area to external balance. Some flywheels come with the mounting holes drilled but because you changed pistons it would still be hit or miss on whether the engine smooths out or not. Best bet is have it done correctly.

[Gregwill16]

+1 ^^ Agree with Dale. Best to do it right and make sure.