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Small block Oiling Routing/Schematics?


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Hello again. Having an issue with not getting any oil to the top end. When we primed and ran the engine, it had excellent oil pressure. Don't know how long the engine sat, but I know it has new bearings. Pulled the intake, pushrods and the lifters and didn't see any oil going to the lifters, even in the rear two. After holding a drill to my priming tool for a good 20 mins-30 mins like a machine shop suggested, we got just a couple of drops of oil to the top of the lifter.

 

Yes, lifers were soaked in oil before installation because they came out of my car that was just running and put them into another small block along with the cam. It seems we have a clogged oil galley/passage somewhere and I'm not sure where to look and how to try and clean it up a bit. I know there are two or three plugs in the front of the block that when removed, should allow access to the plugs all the way in the rear of the block, correct?

 

I'm taking suggestions but also wondering where does the oil go once it gets pumped out of the oil pump? I searched the net and forum and couldn't find anything. I know these small blocks are 'secondary oiling' where the valvetrain gets oil before the bottom end...if I remember correctly. Thanks in advance!

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Chevys use priority main engine oiling. This means oil starts at the crank, flows through holes to the rod journals, and at the same timefrom the mains into the cam bearings. The cam journals feed the lifters, the lifters feed the pushrods, the pushrods lube the valvetrain. If all the oil holes are lined up, you might just need to decrease the lash in the rockers to get the lifters pimpimg better.

 

if not, you have what I like to call a "do over"

 

Andy

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Very interesting. Thanks guys. So it looks like the oil goes to the main oil galley first, then to the front of the engine and through the front cam bearing to the cam journal and then to the two lifter galleys, right? I'm wondering if that front cam bearing has spun or is not lined up with the oil holes in the block....

 

Could I check this by removing the front main oil galley plug and then priming the engine with my priming tool to see if oil is feeding to the main galley?

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Does your priming tool have the 'discs' on it to complete the oiling circuits? I have a home-made priming tool, and it won't pump oil up to the top of the engine b ecause it doesn't seal the oil passeage ways inside the distributor 'hole'.

as soon as I dropped the dist. in and rolled it over a few times, I had oil comin out everywhere smile

 

you will also need to rotate the engine over while priming to move the crank around.

 

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Yeah...that's really what I figured this would lead up to. Not a big deal. Like I said, the engine has one of those aftermarket 'rebuilt' tags on it and the pistons were stamped .040'' over so I know the engine was gone through...just don't know how long ago. I'll see what I can dig into. Thanks all!

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  • 3 weeks later...

Well when I was home, my dad and I briefly checked out the engine. We used my old 350 block to pop the rear cam plug, front and rear cam bearings, and oil galley plugs out of the block to see where oil gets routed. I found that oil comes from the filter, to the pressure tap where the oil pressure gauge is tapped into the back of the block and that also taps into a hole in the main galley about 2 inches from the rear galley plug. Without putting the oil pan back on and putting oil in the engine and priming it with the too, I'm not sure if the main galley is getting oil. If it is, then oil travels to the rear cam bearing and there is a groove cut in the block where the rear cam bearing sits which also provides oil to the lifter galley, which we know for sure isn't getting any oil.

 

I'm guessing we have some junk or debris in one of these passages, or behind the rear cam bearing. Any idea how we can clean this oiling system out? Would that 'Motor Flush' or gasoline/kerosene be a good idea to put in the oil pan and pump through as long as the engine's not running to try to clean out some passages? Sure would beat stripping the block completely bare to have it hot tanked and new cam bearings and freeze plugs installed, etc. Always open for other ideas! Thanks

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