I can not count how many times I've been asked about will this engine fit, or will this oil pan fit?? most times the first question I ask is what style block do you have ?? large or small base ?? BUT there is one exception to that rule I will cover that later.      I'm writing this post to help clear up that question, first this only applies to 10, 12, 14 and 16 HP Kohlers, they used two style blocks commonly referred to as large or small base blocks.     We will start with the large base or eared block used on most WH tractors from 1967 to the last Magnum about 1987, these blocks use the bigger oil pan, and the pan bolts on from the top side through ears on the block, this style oil pan is the one that bolts directly to the frame, the two bolts on the right side that hold it to the frame go from under the frame into blind bolt holes in the bottom of the pan, the pan will hang over the frame some on that side, with the mounting ears on the pan NOT being used.   This is a large base block and pan, note how long the pan is and where it bolts to the block   Here you can see where the pan hangs over the frame, at this point under the frame is where the bolts go from the bottom in to the blind holes in the pan.   The holes outlined in red are the blind holes used to bolt the pan to the frame from the bottom, the holes in green are the ones that hang over the frame.   Here you can see the bolts that hold the pan on, going through the ears in the block.   That pretty much covers the large base blocks.     Next is the small base block used on the shaker plate engines, and some of the mid 60's 10hp engines in WH tractors,  this style block is also common in Cub tractors, and others but we are talking WH here.     The small base block the oil pan bolts on from the bottom of the engine, it does not have ears on the block, the pan is closer to a square in shape than the large base block, here is a pic of a small base block and oil pan.   There are many many styles of oil pans to fit the small base block, other brands of tractors use pans in all shapes, and depths so when swapping this style pan you have to watch how long the oil dipper is on the bottom of the connecting rod, it can be cut to fit a shallower pan, WH used two basic pans on this engine a very shallow pan on the early 10 hp and a mid depth on the shaker plate engines.   This pan is a shaker style pan used in the late 70's early 80's on the shaker engines   This pan is the flat bottom style used on the 1045, 1055, 1075 and 1046 also used on many Cub engines and other brands, the dipper on the connecting rod is very short on the engines that use this pan.   This is a deep pan on a Cub engine, I do beleive it uses the same dipper as the large base blocks with the big oil pan.     Here is a shot of both styles together, to give you a idea of how the blocks look side by side, note on the large base block the cut outs at each end, I will be talking about them and the 4 holes you see where a small base oil pan could fit with a few mods.    Here are the pan gaskets side by side and over top of each other.   Ok now we will talk about how a small base oil pan can be used on a large base block, note the red circles they point out the cut outs in the block where the small oil pan will not seal, this area can be filled up with JB weld or other compound that will stick to metal and take the heat, then note the green circles they show the holes that will need to be tapped to bolt the pan to, so far all blocks I have seen have the holes but are not tapped, with these mods a small pan can be used on this block, also if needed you could cut most of the ears off the block.   Now some blocks (very few) are set up from the factory to except both style oil pans, most common found on JD tractors as they use a shaker mount set up that uses the ears on the block to mount it but still uses a small oil pan, here is a duel pan style block note is does not have the cut outs in the block like a normal large base block does.     Just remember to check the dipper on the rod, to long and it will hit the pan, to short and it may not splash lube properly.     I hope this helps clear up a few questions about block styles and how they differ                       
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