[Jac Mac]

Johny Cobra,
Try this for starters, If you have the pan off check the end float of the crank by prying it forward/ rearward, it should move quite freely and have around 0.005"( magnetic base dial gauge reqd to check ), if you used a rope type rear seal it may be quite tight.

If thats OK check the end float of each pair of rods on each throw. This can be anything from 0.011" up to around 0.020". Each rod should move freely and independantly from the other on each journal. If not you may have a bent rod or even installed one back to front so that the brg shell ( which is offset in the rod ) is riding on the fillet radius of the journal.

Check those above points before looking further, they will cause the most harm if any are present.

Jac Mac