Is a 6223 427 steel crank INT ballanced or EXT ballanced, and can you tell if it is an EXT or ENT by looking at back flange that the flywheel bolts to, also can you mistakenly bolt an Ent bal flywheel and ballancer to a ext bal crank and would it run right.  

Externally balanced dampeners/flywheels will have a small weight attached to the inside rim of the part.

It is best to keep externally balanced parts matched with externally balanced components and vice versa to eliminate added balancing costs. If you just mix & match without regard to the balance you will have problems.  

Sorry I should have said I know the diffrence between EXT & ENT bal flywheels and dampers, I dont know if the flange on the crank would tell the diffrence in cranks.  

It is internally balanced. Bolting on externally balanced flywheel and damper would be bad news. I have not done any 427's, but I'm pretty sure the third counterweight measures 7/8in. thick and the 396-402 measures 7/16in. Your forging# should tell you all you need to know. 7115 is the# that comes to mind for a 427 forging.  

The reason I ask about the back flange to tell if it is ext or int balanced is engine is in car and running great,it has an 11" steel flywheel and balancer that is not EXT balanced.I forgot to get the numbers on crank and can not pull the oil pan ?  

The 3.76 stroke of the 396-402-427 results in the piston pin being further towards the bottom of piston to get it TDC, the only factory EX. balanced cranks were that of the 454-502. If you indeed have 427 pistons, then an externaly balanced crank (4.00 in.) would ram the piston into the head. So I'm shure you have a 3.76 crank. Question is, is it a 396-402 or heavier weighted 427 crank. No way I know of to tell by flange. Did you assemble this engine or install as is?  

It was assembled by a speed shop (forgot name)
, to much stuff to list, I bought car 5 years ago was in the car but wrong motor mounts, doing a complete restoration on the 67 camaro but keeping the motor as is, some know it all said 427 steel cranks came in both EXT and ENT bal cranks,so I started to dought myself I cant find any info on them but cast numbers 6223 427 steel crank is what the guy told me,I put every thing back together but the bottom end.I always worked on small blocks this is my frist BBC and I love the Power,Thanks