ive got a stock,fresh rebuilt 70 hemi engine that is a dog.the engine was built by someone else so i dont know the specs etc but im working on it today and using a piston stop as well as crudely confirming with a dial indicator it appears the timing marks are out by 10 degrees(advanced).
the dampner doesnt appear to have slipped and my buddy (chevy engine builder) says hes seen more than a few few cranks(chevys i assume) that have had the keyway cut wrong causing this,is this likely on a hemi crank?
if the keyway is cut incorrectly then the cam is likely installed wrong as well im thinking,possibly explaining why the motor has no power and runs poorly with black sooty spark plugs.

any thoughts from the always helpfull moparts experts?

im not sure how common it is , but i have seen this problem an a street hemi with my own eyes... so it does happen

There are two different stock timing covers one is aprox ten degrees different.They were used on cast crank big blocks with the large tapered balancers.I have run into this before.Find absolute TDC with a piston stop and correct the zero mark on the tab.Also some of the bolt on tabs that have the sensor adapter are off on the degrees.We always varify the TDC mark on any timing cover during a engine build and find the many slightly off.A few degrees can make a lot of difference,especially on a hemi.

Sure it didnt slip ,

On my B/496 the timing marks were off 10 degrees. I believe it was caused by my repop timing cover and perhaps factory tolerences... regardless I am glad I checked like you did... first with plug hole stop then with dial indicator/head removed. Both methods gave the same position for true TDC.

Mopar, in all of it's infinite wisdom made two different balancers and timing covers for both the wedges and Street Hemi motors. The early ones, I belive 1967 or 1966 and below used a timing cover with a straight timing tab on them and balancers marked to match that cover(the zero mark is up high almost at the top of the timing tab) The later ones use a curve timing tab on the timing cover that has the zero mark about halfway down the tab and the matching balancer Why would they do that, Goverment intervention, for smog emmision reasons

Like Cab and Bob said....different timing covers/balancers for sure....and out 10* just as you say. I ran into this when I built my stroker....I sure make it a must now to double check TDC markings. Down on power, black plugs, hesitation......

Thanks guys,im sure my cover and balancer are mismatched,good to hear that others have seen this firsthand.
this engine also has the 1hemiman ebay rocker assemblies(ontario canada) on it which my motor guy insists must be replaced,so Im scrounging for rockers now too.
I can get my hands on a set of stage V's fairly quickly but they were used in a fuel car which scares me a little......

We have seen the E-bag rockers with ratios all over the place and seen first hand the adjusters pull through the threads.