Hugh,
If it helps, your 2nd paragraph describes the factory configuration for the blocks; then your question on the statement of 3-1/8" sleeves for the early ones introduces a new topic of what's commonly available today through the aftermarket engine kits.Today's aftermarket kits are either 3-1/8" overbore (meaning thinner sleeve, larger piston) kits, or 3-1/4" overbore kits. The 3-1/8" kits are for the A/B/C/early Super A (before SN 310300) tractors that originally had 3" bore, as well as the 130/140/230/240 blocks that came with thinner sleeves from the factory. The 3-1/4" kits are for the Super C/late Super A (310300 and later)/100/200 tractors. The one exception is a group of 500 C tractors during the demo program in 1950 that had special blocks, they should also use the 3-1/4" kits. Of course this all assumes the factory block is still on the tractor, which can't be assumed after 50-60 years. With minor exceptions (A/B blocks w/o provision for hyd pump; and x40 series blocks with different water pump arrangement) these blocks can be (and many have been) interchanged quite easily. Which is why we keep repeating for people to pull a sleeve and measure the O-ring sealing OD (3-5/16" vs 3-7/16") before ordering any parts. Paul,
only the later C-123's were cast with the C-123 ID in the block (after Super A/Super C's) since the same block was used for two different sized engines as Hugh noted above.
Stan(VA).
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