I installed a new mechanical fuel pump on my slant a couple months ago, and it's been doing just fine, until today... it's very hot out, and the engine is really getting up there in temp, too, and I think this may have attributed to it, but I was driving along when my engine died. I checked my fuel system and found the two mounting bolts to my fuel pump to be quite loose, and when the engine cranked, the fuel pump would just wobble, instead of pumping. I tightened the bolts back down as tightly as I could with my fingers, since my wrenches were at home, and managed to drive it for about a block before they were loose again, and only finally managed to keep it running by wedging a chunk of metal between the pump and the wall of the engine compartment to hold it in place. I'm wondering if using threadlock would be effective enough for holding those bolts in, it's quite unnerving. The pump is so hard to get to that I don't want to do any more work down there than I possibly have to. Any advice?

Btw... 1977 Plymouth Volare, 225 Slant six, 1BBL Holley

You shouldn't have to use loctite on it, but if you want, use the weaker blue kind. I never used anything on mine when I was running the mechanical pump. I believe the screws had washers on them though, not sure if they were locking or not but lockwashers sure wouldn't hurt either.

Are the base of the pumps the same thickness? If the newer pump is thinner, then the screw may be too long and bottoming out, not allowing you to tighten it fully.

all the pump bolt i have seen have a washer shoulder built into the head off the bolt,i wouldnt use a washer it might help the bolt spin just give them a good turn.