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02-23-2004, 01:21 PM
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crank main oil holes
Hey guys,
What do you think of the multiple oil holes on the mains? I have never seen that before. Is it a cheap way to try to get better oiling? I am planning on buying this block but I would like to get some feedback from you experts before I make a decision. Thanks guys! 
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02-23-2004, 04:29 PM
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Bump
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02-23-2004, 05:08 PM
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I know you wanted advice from an expert, but i'll put in my $.02 anyway.
If your journals are cross drilled and chamfered, that will supply all the oil your bearings can use, unless you have an oil pump problem. The more holes that you poke in the crank, the weaker it will get accordingly. I would put away the cordless drill and concentrate on cleaning th oil galleries, and adding a high volume oil pump.  kitkar
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02-23-2004, 05:54 PM
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Thats what its supposed to look like. One hole goes to the cam other two are from main oil galley & to the lifters.
I think you just wanted to show off your 4 bolt main block. 
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02-24-2004, 09:10 AM
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Looking at the block in that picture, you can see that the main oil passages in the bulkheads supplying the main bearings have been drilled double wide, and triple wide on the top hole... now having only worked on Chevy small blocks, I don't know if this is a difference in design... but doesn't that seem a little odd? even if you supposedly reduced restriction up where the bulkhead oilers contact the bearings, aren't you still going to have restriction through the oiling hole in the bearings?
Regardless, it's not going to change the overall pressure in your oiling system unless you upgrade the pump... perhaps you could restrict the cam shaft oil supply and gain pressure to the rest of the system, but drilling out the block at the mains definitely doesn't seem like the right approach. If anything, you're taking away contact surface from the bulkhead to the bearing, causing less efficient heat transfer from the bearings to the block. What's with the block sitting outside in the snow? Be careful... 2 cents the blonde weasel san diego, ca okay, reading greg's response to the post confirms that i'm talking about SBC's and he's obviously not... what kind of block is that? obviously it has a different oiling system than the SBC. bw Last edited by blndweasel; 02-24-2004 at 09:10 AM.
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02-24-2004, 09:35 AM
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Any 1980 or earlier Motors or Chilton manual will have the oiling diagram on that Pontiac and should put an end to all the silly theories that the picture is engendering.
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02-24-2004, 09:59 AM
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Well, yeah, if its a pontiac block... forget everything I said.
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02-24-2004, 10:28 AM
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Thats just the way the factory machines Pontiacs for oil. The hole in the bearing controlls the flow to the crank.
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02-24-2004, 10:37 AM
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Thanks for the responses guys, it helped a lot. Sorry I forgot to mention the block is a '72 pontiac 455. I would also think the bearing would restrict the flow no matter how many holes are there. Just wanted to see what you guys thought. Thanks again!
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02-24-2004, 04:20 PM
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I"ve seen lots of Pontiac blocks like that. I worked for GM back in the '70s at the Chevy engine plant and when we got a real lame brain SFBs machinist in the group, he'd get shipped off to the Pontiac engine dept where they let em go nuts on the blocks with the air drills!!!
( just kidding!) Mark
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