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Rear main cap and oil pump compatability


Local time
3:45 AM
Sep 19, 2023
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I had a 318 short block built for me and I purchased a Melling M-72 oil pump separately. When going to install the mounting neck will not fit and I don’t want to force it. I check with my junker short block and it fit. The new rear cap is stamped 5-31 old (which fits) is stamped 1-31 can someone please explain what these mean and direction to the correct pump. I prefer not to disassemble the new block.
Check the main cap bolt or nut is not protruding into the oil pump hole diameter sometimes they need a lick taken off
I don’t understand how the bolts would affect my issue. The cap bolts are on either side of the hole for the pump neck. I’ll try to explain… so the oil pump shaft inserts from top of engine into the oil pump (neck) loacted on the bottom on the engine through the rear main cap. Determined my “new” block is a 72’ and old was a 69’. After referencing w/rock auto the pumps are all the same for these years. I did have installed a mild rv camshaft hmmm???
In the Melling instructions it warns you check hole in the cap will accept mounting neck of the pump.
Check for burrs on the bearing cap.
Carefully file down the oil pump until it drops fully in to position. Be careful to keep any metal out of your new engine.
I mean only relieve the area of the pump that goes in to the bearing cap - if that was not clear.
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Also if the main cap bolt or stud is too high it can stop the pump from going all the way down causing it to leak
It sounds like he has the stock bolts but it is something to check.
Get your round file out...
Think of car repair like carpentry. The 2x4 you buy at the lumber yard might fit but most will need to be massaged.
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