The Stovebolt Site Forums The Shop Area Engine Shop 235 timing plate screws

The three flat head 5/16 -18 screws that bolt the back timing/front engine mount plate to the block were damaged when I removed them. Bought some new ones (had to shorten them to 5/8" like the originals). When I tried them, the back plate is loose. The bolts are not too long, the bevel on the bolt hits the block before the bevel tightens down on the countersink of the back plate. I can make it work by undercutting the bevel of the bolt to the minor dimension but that seems a bit strange that I'd have to do that. Any ideas?

That's the way any replacement screw needs to be modified. Look at the original screw and make the replacement look just like it. That one was custom made for that application, apparently. I usually lathe turn a hex head bolt to fit there and hacksaw a screwdriver slot into it.
Jerry

Thanks Hotrod Lincoln. It's in 3rd gear from now on. No more reverse (I Hope) for me. Now where did I put that cam.

Another option would be to relieve the block a little with a countersink to accommodate the taper of the regular flathead screw head. Losing a thread or two won't cause any grief, and it might be simpler than tinkering with the screw heads.
Jerry

Tannin, I think that we have all encountered your issue in the past. Those flat head screws can be a bear to remove and often get damaged beyond being able to use them again, or they get damaged when someone tries to tighten them too much with too small of a screwdriver. Either way, the slot gets mangled.

I stumbled across something that works really well with either removal or tightening. I use a hand impact wrench, the type that you hit with a hammer to make work. I took a 1/2" hex head bolt and ground it down so that it has a tip that is the thickness of the screw head slot. The hex head fits into a socket on the impact wrench. Using this device makes it easy to remove the screws (and save them!) and also allows good tightening when replacing.

Won't help you with your mangled screws, but might help you when installing new ones.

Matt

I appreciate the info and tips. I found a 5/16"-18 undercut flathead machine screw (1/2" and 3/4") from Fastenal. $0.22 for steel and $0.44 for stainless. I ordered some of each. I'll let you know how they work out. I think I put the cam in my bedroom closet. Hope my wife didn't throw it out.

Bob

Be careful installing SS screws, they like to gall and bind, make sure you use never-seize on the threads.

Mike B

I knew what I was doing by ordering both steel and SS. I just didn't know why. It just makes sense to do it the way they originally did it. I'll stick to the steel to make my life easier. Thanks Mike.