I am in the planning stages to replacing my c-6 with a ZF-5 speed. The transmission came from a 1989 donor truck which included the original 460 engine, albeit junk. I am unsure as to whether the 1989 was internally or externally balanced, nor do I know if my 460 is internally or externally balanced. My 460 is a conglomeration of parts assembled by a local engine builder so the year of origin is not known. How do I determine the balancing method?

Also, I read in a post that not all 460 cranks contained a pilot hole. Can anyone give me a statistic on that and/or the best alternative if mine does not?

Thanks.

 

I've done some additional reading on the site and have determined the donor truck (89) was externally balanced because it had the "hatchet" weight. Due to my intimate knowledge of my current 460, it is internally balanced as it does not have the weight.

Now my question is: If I utilize the external "hatchet weight" along with the flywheel from the 89, will I have balance issues? As I understand it, the "hatchet weight" and the collar from internal balance motors are interchangable, correct?

 

The crankshaft, crank spacer, and flywheel(or flexplate) need to be all the same type. That is, internally or externally balanced. Also an internally balanced crankshaft may have counterweight throws that hit the bottoms of the cylinders of an externally balanced block. The 460 switched to external balance in about 1979.

There are many detailed posts on this subject...

-john

 

you will need to find a earlier than 1978 flywheel for internal balance engines, and the pilot hole should be 1.375 dia.

 

i believe the zf tranny need a different flywheel than the standard older 460 flywheel. i believe both the OD as well as the clutch bolt pattern is different. i remember reading a while back about a guy who built these flywheels. seems they were in the $200-300 range. was the reason i never but the zf in and stayed with my c6 and bought a gear vendors. the kit also came with the correct pilot bushing that fit the older 460 cranks. when i say older, i mean pre F/I motors. seems like the starter wont make contact with the flywheel with the older clutch, and the bolt pattern wont accomidate the clutch. the 460 f/I motors had an even different blanace, so that wont work either. went aroun and around and i gave up. you could probably make the newer flywheel work, just need to have it staticly balanced by a machine shop. just like balancing a motor.. but once again, theres another 100 plus the flywheel 50, and machining it 35, and youre up to 185 again.

Kurt