Oil restrictors for bbc....when and why
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Oil restrictors for bbc....when and why

  1. #1
    Senior Member H20MOFO's Avatar
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    Default Oil restrictors for bbc....when and why

    I dunno....should I be running restrictors? I have a solid roller cam, and a set of crower hippos. I have to admit I don't even know WTH they go. I have my intake off at the moment thought now might be a good time to figure out if I have/need them. As far as max r's I'm only 5500 on a good day. I want to be able to idle and pull kids ect. without worrying about the cam. If it matters it's a mark 4 bowtie tall deck. Thanks in advance for putting up with all my rookie questions.
    Another Hot Boat refugee

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    No, you do not need them.

    Restrictors band-aid a problem with poor drainback from the top of the cyliner heads, a problem comon to Oldsmobiles at high revs, not to Chevys.
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    Senior Member CK7684's Avatar
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    From what I have heard, when running roller rockers, you can pump too much oil up top. (they require less oil) I'm still trying to figure out my oil pressure issue and thats how I can accross this info. Not sure at what point they would be needed though. Sometimes the oil is already restricted from lifter and/or pushrod design...

    (I'm no expert though, so do your homework!!)

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    Sit N' Spin Jetaholic's Avatar
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    I'm running a 450-500hp build with no oil restrictions and with a high volume oil pump (Melling M77HV) I'm seeing about 60 at cruise and 70-75 at WOT.

    With a solid lifter cam and roller rockers, you CAN run oil restrictors. They make the ones that screw in place of the oil galley plugs on the side of the block. But you CANNOT run them with a hydraulic cam for obvious reasons. However, I don't think this will cure your problem.

    Since you're running a roller cam you don't have to worry about it going flat.

    What oil pump do you have? What is your oil pressure at cold idle, hot idle, cruise and wide open?



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    Senior Member ap67et10's Avatar
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    I asked this question about a year and half ago because i was switching to solid roller from hydraulic roller. what i was told is that there is no need to use restrictors because the chevys don't have bottom end oiling issues. not to mention that most guys like the extra oil up top for valve spring cooling. which is the biggest reason people said to NOT run them. the extra oil is useful for the springs and you won't be causing any lower end starvation issues anyways.

    AP

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    Senior Member H20MOFO's Avatar
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    The way I understand it the mark4 is not a priority mains oil system. I assume the restrictors send more to the mains/rods. But like I said I don't even know where they go, or if I have any already.lol I don't think I have an oil pres. issue, I've always got 50+ on the gauge. As far as the pump, it's a mellings high volume, not sure the exact # my build sheet is at work.
    Another Hot Boat refugee

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    Sit N' Spin Jetaholic's Avatar
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    So you have a general understanding of how oil flows through a MkIV BBC (figured this out while I was building my motor a couple of months ago)...

    Oil flows through the pump and splits off. One side of that split feeds the lower end while the other side of the split provides the upper end oiling (i.e. lifters, pushrods, rockers, etc etc).

    The lower end side of the split flows through the thrust bearing cap, into the thrust bearing, where it splits to flow into the oil filter, while some of that oil flows into the #5 cam bearing (the thrust bearing, #5 cam bearing, and the upper end get direct oiling). It then flows through the oil filter, into the driver side pan rail passage where it splits off to main webs 1-4.

    As soon as the oil has entered main webs 1-4, it splits again. Some goes to the main bearings while the rest goes to the cam bearings. Oil flows from the main bearings, where it is pressure fed into the crank and flows through the crank to get to the rod journals to oil the rod bearings.

    On the upper end side of the main split, oil splits again to feed the passenger and driver side lifters. On the driver side, oil has to basically jump over the distributor shaft hole to get to the driver side lifters. This is why either a distributor or a special oil pump priming tool has to be installed for oil to reach the driver side lifters (a machined groove in the dizzy shaft or priming tool makes up the other half of the oil passage around the dizzy shaft to get through the dizzy shaft hole). Oil then flows into each lifter, where it flows up through the pushrod, then into a hole that runs from the pushrod seat on the rocker to a squirt hole at the top of the rocker. This oil is in effect "squirted" onto the rockers where some of it makes its way onto the valve springs as well.

    Oil that flows into the heads drains through a drain back hole in the head, back into the lifter galley where it drains through the rectangular holes above the cam, then back into the oil pan.

    The pistons and wrist pins are splash oiled from the oil that gets pushed out of the rod bearings (I think...someone correct me on this if I'm wrong).

    To answer your question, if you're running 50+ PSI oil pressure then you don't have a pressure issue and you don't need restrictors on a Chevy big block. Chevy's never had upper end oil drainback issues that other motors tend to have so they're not needed.

    Hope this helps.
    Last edited by Jetaholic; 07-18-2009 at 01:59 PM.



    Quote Originally Posted by HammerDown
    Kendall L-427 Super Blu...extreme-pressure (ep) lithium complex keeps my thrusting balls happy
    Quote Originally Posted by back2k5 View Post
    Well I am putting in a nice stereo system in the Carrera...maybe Ill put on some rap and turn the scoop sideways

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    With roller rockers you CAN reduce the oil to the top, you don't NEED to.

    If you restrict it, you MUST go to roller rockers away from the factory ball-rockers, or they will die very soon.

    I run a stock (non-High-Volume) oil pump, run about 45-50PSI cruising under 4-grand, 60PSI wound flat out under 6-grand, 10-50 Synthetic. 23psi hot idle after a 4 or 5 mile WFO run. No restrictions anywhere, as factory. 2-qt K&N filter on the stock pad. 5 years now.
    Hydraulic flat cam, roller rockers.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    Senior Member H20MOFO's Avatar
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    Quote Originally Posted by Jetaholic View Post
    So you have a general understanding of how oil flows through a MkIV BBC (figured this out while I was building my motor a couple of months ago)...

    Oil flows through the pump and splits off. One side of that split feeds the lower end while the other side of the split provides the upper end oiling (i.e. lifters, pushrods, rockers, etc etc).

    The lower end side of the split flows through the thrust bearing cap, into the thrust bearing, where it splits to flow into the oil filter, while some of that oil flows into the #5 cam bearing (the thrust bearing, #5 cam bearing, and the upper end get direct oiling). It then flows through the oil filter, into the driver side pan rail passage where it splits off to main webs 1-4.

    As soon as the oil has entered main webs 1-4, it splits again. Some goes to the main bearings while the rest goes to the cam bearings. Oil flows from the main bearings, where it is pressure fed into the crank and flows through the crank to get to the rod journals to oil the rod bearings.

    On the upper end side of the main split, oil splits again to feed the passenger and driver side lifters. On the driver side, oil has to basically jump over the distributor shaft hole to get to the driver side lifters. This is why either a distributor or a special oil pump priming tool has to be installed for oil to reach the driver side lifters (a machined groove in the dizzy shaft or priming tool makes up the other half of the oil passage around the dizzy shaft to get through the dizzy shaft hole). Oil then flows into each lifter, where it flows up through the pushrod, then into a hole that runs from the pushrod seat on the rocker to a squirt hole at the top of the rocker. This oil is in effect "squirted" onto the rockers where some of it makes its way onto the valve springs as well.

    Oil that flows into the heads drains through a drain back hole in the head, back into the lifter galley where it drains through the rectangular holes above the cam, then back into the oil pan.

    The pistons and wrist pins are splash oiled from the oil that gets pushed out of the rod bearings (I think...someone correct me on this if I'm wrong).

    To answer your question, if you're running 50+ PSI oil pressure then you don't have a pressure issue and you don't need restrictors on a Chevy big block. Chevy's never had upper end oil drainback issues that other motors tend to have so they're not needed.

    Hope this helps.
    Thanks Jon, and everybody.... I've put together a couple of motors(4)lol, I remember the oil hits the rear main 1st, but as far as the upper deal(to the rockers ect.) I'm lost. Where do I look to see if I have them(restrictors)??? Pull the pan or back motor plate or??? I just blew up a roller rocker, just covering my bases(I hope).
    Another Hot Boat refugee

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    Default Upper end restrictors

    Quote Originally Posted by H20MOFO View Post
    Thanks Jon, and everybody.... I've put together a couple of motors(4)lol, I remember the oil hits the rear main 1st, but as far as the upper deal(to the rockers ect.) I'm lost. Where do I look to see if I have them(restrictors)??? Pull the pan or back motor plate or??? I just blew up a roller rocker, just covering my bases(I hope).
    BBC oil restrictions go in the BACK of the engine where there are usually two 1/4 NPT gallery plugs, NOT in the side oil plugs. The side plugs only purpose is to fill holes needed to drill the passages towards the center of the engine. Common restrictors have a .060 hole to feed the lifter gallerys when using solids or roller lifters that don't require the same amount oil as hyd lifters. I have always used them in the PS motor with success..........Ray
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    Sit N' Spin Jetaholic's Avatar
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    Quote Originally Posted by Moneypit View Post
    BBC oil restrictions go in the BACK of the engine where there are usually two 1/4 NPT gallery plugs, NOT in the side oil plugs. The side plugs only purpose is to fill holes needed to drill the passages towards the center of the engine. Common restrictors have a .060 hole to feed the lifter gallerys when using solids or roller lifters that don't require the same amount oil as hyd lifters. I have always used them in the PS motor with success..........Ray
    Thanks for the correction Ray. H20, on a standard MkIV block you'll see a couple of oil plugs on the back of the block behind the flex plate. There will be one on each side of the cam plug...I'm pretty sure these are the plugs that Ray is referring to. That's on a regular OEM MkIV block...since you have the bowtie block they may or may not have these plugs there.



    Quote Originally Posted by HammerDown
    Kendall L-427 Super Blu...extreme-pressure (ep) lithium complex keeps my thrusting balls happy
    Quote Originally Posted by back2k5 View Post
    Well I am putting in a nice stereo system in the Carrera...maybe Ill put on some rap and turn the scoop sideways

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