[GOSFAST]

Building these for a living we strongly recommend using washers between the head bolt holes and the nuts regardless of the casting material, aluminum or iron.

We would never run the aluminum w/o the washers. It helps "save" the castings and stops the nuts from "digging" into them as well.

We have "special" thin washers specific for this application, we use them on all the 100% stock-appearing SB and BB Chevy's we build and we use them on all our Flathead's as well! They are barely noticeable when installed.

Thanks, Gary in N.Y.

P.S. Here's a couple shots of some fasteners with them, you can see how "thin" they really are!