Just did the black oxide 5/16-18 thru bolts on my Berk today. I am almost ready to put the BBC 8-71 EFI project in the boat but I had to change to a stainless impeller and wanted to thru bolt the loader/grate set up. This was by far I think one of the best mods to do. It took in total of about an hour and a half, taking my time and locating the right tools. The hardest part was taking the tiny 1/4 inch bolts out of the grate/intake housing. I used a makita impact scew gun. I cannot believe how cheap and short these "stock" bolts are. After I got the loader/grate out I clearanced the holes in it for the 5/16" bolts. I also re-countersunk the loader/grate plate to match the larger heads of the new bolts with an 82 degree countersink bit. All this can be done with hand tools. Drilled the intake housing holes out with a "G" drill and then tapped them all the way with a 5/16-18 tap. Buttoned everything up with locktite and good to go.
T.J.
