Golden Jubilee
Posts: 530
Joined: Sat Dec 01, 2012 9:55 am
Re: BD240 Overhaul - General Questions
"I just take my 1940 Quickway boring bar, and put it on a steel plate, which is C clamped to the rear of the block. Nice and flat, on the rear surface. My old boring bar, which probably hasn't bored 100 engines, is held down by a 1/2-13 or 5/8-11 bolt. I put the bar on the plate, snug the bolt, just tight enough to let me move it with a lead hammer. Put a dial indicator on the bar, put it in neutral and spin it, tapping it till it is within .001". Tighten it down, I recheck, and bore a hole, .375" deep (3/8") and 4.562" in diam. (4 9/16") ID. This is done with the rear main cap torqued. You don't need to mess with a bearing at this point. Just indicate in the bore, where the bearing fits in to. Take off the cap. Clean everything spotless. Put the engine together, and seal up the rear main cap to the block. I use orange high temp silastic, or silicon, or industrial RTV, only use GE or Dow Corning. At this point the crankshaft should spin, with a little oil on the brgs. like a kids top, cause it has no seal drag. If it does, tap in the seal. This will seal up the ass end and put a little drag on the crank. Always lube seals on installation. I don't use the primitive old felt wipers, I use seals ---Caution---don't knock the spring off the seal by doin sloppy tapping. If you look inside the seal, before you install it, you'll see what I mean. I have a seal in hand and it says National 335942N USA Tells you what I know. It came out of a brand new Chicago Rawhide box with 39838 on the box. I buy these at a power transmission, or industrial bearing house."
I took Alex's information with the seal that came in my FelPro gasket set, the block, caps and bolts, to the machine shop. I think the long and short of this is that you want them to bore 3/8" into the back of the block, 4.562" diameter. Here are pictures of the end result. You can see that the old groove for the rope seal isn't used at all, so the modern seal rides on a "new" spot on the crank that doesn't have that seal wear.