just finnished a new 406 but for some reason it has a terriable vibration that the old 406 didnt have,im using the same fly wheel and balancer as before. the rods and pistons are all equal with in a gram from heaviest to lightest....the block was line bored as i didnt have mains.any ideas as to why ? thanks tao

 

Are the two cranks the same? I don't know my 406's, but if one is externally balanced and one is internally balanced, that would account for vibrations.

Other than that, only things that come to mind are bad mounts, or a balancer that's coming apart (you can see em wobble when they do).

 

that did come to mind ... im checking my part number just to make sure ... but i dont remember seeing any slugs in the new crank ... but then i havent ever seen what they look like so if they dont stand out i could have missed them ... thanks tao

 

Is the harmonic balancer new or used?

 

the balancer is used but it came off of my old 406 ... it appears to be in great shape ... i did have a new ring gear put on the fly wheel when i did the tranny ... the vibration seems to peak at 2100 rpm and smooths out by 3000 rpm ... it doesnt matter if im moving or sitting still,clutch in or out ... although from outside under the hood i dont feel it at all ,just when im in the drivers seat. i may pull the bolt for the balancer just to see if the key way is lined up. maybe the key fell out during assembly and i missed it ... could the input shaft of the tranny be bent?or would that go away when i push the clutch in?im going to pull the tranny this next weekend just to narrow it down,unless ???? tao

 

I am having a similar problem with my 350 build. Let me know if you think it was the input shaft, I have suspected that as well.

 

i dont think its the input shaft as im on the third tranny since i started this thread ... im kinda ignoring it for now ... gonna pull the eng and tear it down
ill post if i find the problem