The Stovebolt Site Forums The Shop Area Engine Shop blocking

I think the term "blocking" refers to that process where machine shops remove a certain amount of metal from the engine block (block resurfacing). I have an otherwise good 261 block, except for rust/corrosion spots in the compression area on top (the circular area not covered by the head gasket). Can this 59 to 62 261 block stand 1/16" surface metal removal with a stock -848 head? with a shaved -848 head? The amount of metal necessary to clean up this block may be as little as 1/32", its hard to measure. In other words, is there a known and safe amount that can be removed from any stock 261 block? Thanks...Ron B

It's called "decking", and 1/16" would be far too much to remove. That's .0625", and the usual amount of block machining is about .015" or so, just enough to level out the gasket sealing area, and correct any warp. If the head gasket sealing area is badly pitted, there's another way to correct the problem. Is the block being bored as part of the rebuild? If so, have the machine shop install some short sealing rings made from a cylinder sleeve slightly larger than the bore size, stopping just above the travel of the top piston ring. I've saved blocks that had grooves eroded in them from running with a blown head gasket for a long time this way. If the repair ring is installed before the rebore job, it will be almost invisible, and very effective after the block is rebored for the new pistons. I've cut repair rings from a 1/8" wall cylinder sleeve and installed them in several damaged blocks, then run them in race engines, without any failures. "Flanged" cylinder sleeves are also available for such repairs, but they're pricey, and installing all 6 of them would be more expensive than finding another block to work with!
Jerry

I believe what you are alluding to is called "having the block decked" and the head milled. You will surely need to take your head and block to a reputable machinist and have him check it out. If he says- "I think" or "maybe" then grab your stuff and leave. He should be able to check the head and block and tell you for sure if what needs to be done, can be done. A good machinist is an invaluable tool to the engine rebuilder. Find one you can trust and relate to. His price is never "to high"..

Didn't mean to come right in behind ya Jerry. Good info.
If I'm ever in Ten. and need some machine work done I think I know "the man to trust"-LOL

Jerry, due the the thick decks on 261 and the somewhat low power out even when modified,60 thousands is within reliability limits.Guys who do vintage drag racing will take off as much as .100 for whatever reasons.My "hot rod" 261 is decked .025 and a fairly stock 261 in my other trucks was decked .035. Neither one has had any problems with related to headgaskets in 6 years.You may or may nor have intake valve to piston interference depending on where the piston sits at TDC and your choice of cams. 261 stock type pistons are anywhere from .020 to .040 below the deck at TDC.

Block decking requires test-fitting the crank, rods, pistons and bearings to be used. A measurement is taken to determine the distance between piston at TDC and block deck. That measurement is recorded and the engine dissassembled again. Then the deck of the block is cut by that much. This is called "zero-decking" the block. Any more than that and the pistons will stick up past the block deck at TDC.

If the rust pitting is not where the head gasket seals off, then it is not a problem. As long as the rust pits don't compromise the water jacket or something weird its normal.

Yep, Tony, I keep forgetting those stovebolts have more iron than the average battleship! I hope he finds a good machinist who won't just whack away until it's smooth, and maybe put the pistons into the head!

I always begin machining a block with a line-bore job, as every other dimension indexes off the crankshaft. A very light decking job comes next, so the cylinders will be square with the crank. (I'm still using an antique Van Norman boring bar that squares up to the top of the block) After getting all the rods equal length, I do a test assembly and measure for final deck height. On the block we're discussing here, unless the sealing area of the head gasket is compromised, there shouldn't be a problem, just do a light decking job to make sure it's flat, and bolt it together!

Oly, drop in anytime! I'm sure I'll learn a few tricks!
Jerry