I drill the heads bolts out to 9/16 on my drill press and hand drill the pushrod holes to 17/32. Make sure they slide in by hand but not sloppily. I mix up enough JBWELD to do one head and just put a very thin coat around the end of the tube I am pushing in and drag one thin line down apart of the tube away from the pinch where I will be grinding. As up tap it in it spreads itself. I usually put a chamfering bit in a hand drill and chamfer the two head bolt holes I drilled so I know I didn’t leave a ridge. Remember don’t mix a lot as it takes like a one inch thin line of epoxy and hardner side by side before mixing. I’ll usually slide like a 7/16 bolt in the 9/16 tubing so I can tap it softly with a ball peen hammer and not damage it.
