The Stovebolt Site Forums The Shop Area Engine Shop Engine bolt spinning?

If the nut is rusted to the bolt threads you are not going to be able to hold a carriage head. So you either tighten the nut with a big impact driver until bolt breaks or you cut/slit/split the nut with an angle grinder and die grinder and chisel it off. Cut thru the slots in castle nut (and thru bolt) and don't take any prisoners. Time to go nuclear.
Do whatever you have to do but don't replace with carriage bolts!!!!!

Seems there is a clearance issue with using hex head. I'm not familiar with this area and how much clearance there is BUT.... for reassembly if hex head won't work, I would consider a 1/4 thick plate up top with threaded holes to receive bolt from bottom. Length of bolt will need modified to stick thru plate 2-3 threads and not hit whatever. Use flat washer and lock washer under head and mild locktite on threads. Could be one plate with two holes which won't spin or two plates that may hit crossmember and not spin....or use an anti-spin device. 7/16 head is .297 thk so not much help with a 1/4 plate. Depends on where the interference is as to reducing bolt size/nut thk/plate thkness for designing a remedy. PDlighting indicates a remedy.

I still don't understand where carriage bolt goes, Kevin says inner are carriage and shows a pic with them at outer? Carl says carriage are outer. The conversation says hex was used where they were not supposed to be used?..and it worked.