and according to the ad it is externally balanced.

7. THE CRANKSHAFT IS BRAND NEW AIRCRAFT QUALITY PRO-COMP CAST STEEL 4.250 2 PIECE REAL SEAL CRANKSHAFT.THE CRANKSHAFT IS SHOT PEENED FOR STRESS RELIEVING AND HAS A FULL .125 RADIUS ON THE MAINS AND ROD JOURNALS!, THIS CRANKSHAFT IS ALSO EXTERNALLY BALANCED AND IS THE BEST OF THE BEST!!(4.250 STROKE, 1/4 INCH LONGER THEN STOCK 454), FRESHLY MICRO POLISHED AND STANDARD ON THE ROD AND MAIN JOURNALS.

8. THIS ENGINE IS FULLY BALANCED ON OUR NEW RMC COMPUTER BALANCER AND IT IS ALSO BLUEPRINTED. PISTONS, RODS AND CRANKSHAFT ARE BALANCED TO LESS THEN 1 GRAM. ( MOST MACHINE SHOPS ONLY BALANCE TO A 5 GRAM SPREAD) BEARING CLEARANCES WERE SET AT .002 ON BOTH THE MAINS AND RODS.

So what do you think would be the correct one's to put on this engine.

at this point i would suggest that you take the complete rotating assembly along with your flywheel&balancer to a competent machine shop and have the balance checked out,it is obvious that you have a problem and cannot run the engine as it is.

I would have to agree. their ad says it is externally balanced to less than a gram but if it did not come with a flywheel and balancer then you dont know what they used when they balanced it.

Ok, sorry to be blunt...what you bought is junk ! sorry 1st nobody balances a stroker assembly with out the specific balancer and flywheel ! most all stroker cranks I've seen use a non-counter weighted balancer/flywheel..aka scat/eagle...next those pro-comp heads are about as junk as they get..sorry again...but selling for that $$$ what did you expect ? thats about the cost of a good pair of aluminum heads...now what you might do is ck the crank and see if in fact they say interally balanced...you may swap in a 427 balancer/flywheel and get it smoothed out...

I hate to tell you this, but a buddy of mine bought a 496 from these guys last year to put in his 63 Impala. Long story short, he had to take it to a local machine shop and spend another $6k to make it right. Most of the internal parts were junk and unuseable. Engine would not even start when initially installed. Funny thing, I tried to discourage him from buying it in the first place.

I have read some reviews on this shop and there about 50/50, i didnt have much imput when this, when the engine was purchased but its what i got. it runs good, its just the vibration, i emailed a few other people that have bought these engines this morning and one of them said he is running an external balanced 454 fluid balancer and a flex plate off a 427 and took them down and had them balanced togrther and he said its running great.

Are you sure the flywheel is mounted correctly. If the dowel pin has been removed from the crank and you do not line it up correctly you will get one hell of a vibration even at idle.
I learned this he hard way when I was younger.

I did the exact same thing! The dowel pin had been removed just like you stated. Started it up and it was terrible! The counter weight was 180 degrees out! Won't take you long to figure out something is terribly wrong!

If your friends is externally balanced ,running a 427 flex plate makes no sense.427 flywheel is neutral balance .