Unless a customer is willing to install lifter bushings or oversize lifters in a big block Chevrolet with factory block you have a very good chance of loosing a cam lobe. lifter bores in factory block are more often than not in the wrong place centering a lifter on the cam will not allow it to rotate and will cause a failure.we wont warranty any flat tappet cam unless the lifter bores have been corrected.this may be what you ran into with your former builder but you should have been made aware of the high risk you were taking before the build.Bill