Hi i just rebuilt a 1973 1600 vw engine when i got to the push rods and installed them the valves where so tight i could not adjust them i ordered a set of cut your own length rods cut them to 10.65 but still had to shim them to be able to adjust the valves i put engine back in turned it over and it sounded like it was sucking air would not fire wondering if you had any ideas on that thanks