I was reading my service manual. (oil pressure)

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903
Location
wa state
The part I have bolded below has me wondering, why would there be a restrictor in the head gasket? Is this to lower oil pressure? If so, why would the head need lower pressure? I have my oil pressure sendor mounted in the head, I wonder if this is why my oil pressure goes to [email protected], and then stays there till 6150rpm redline....
Quote:
OPERATION Engine oil drawn up through the pickup tube and is pressurized by the oil pump and routed through the full-flow filter to the main oil gallery running the length of the cylinder block. A diagonal hole in each bulkhead feeds oil to each main bearing. Drilled passages within the crankshaft route oil from main bearing journals to connecting rod journals. Balance shaft lubrication is provided through an oil passage from the number one main bearing cap through the balance shaft carrier support leg. This passage directly supplies oil to the front bearings and internal machined passages in the shafts that routes oil from front to the rear shaft bearing journals. A vertical hole at the number five bulkhead routes pressurized oil through a restrictor (integral to the cylinder head gasket) up past a cylinder head bolt to an oil gallery running the length of the cylinder head. The camshaft journals are partially slotted to allow a predetermined amount of pressurized oil to pass into the bearing cap cavities. Lubrication of the camshaft lobes are provided by small holes in the camshaft bearing caps that are directed towards each lobe. Oil returning to the pan from pressurized components supplies lubrication to the valve stems. Cylinder bores and wrist pins are splash lubricated from directed slots on the connecting rod thrust collars.
 
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18
Location
granite city IL
It is most likely not to limit pressure, but to limit flow to the head. The reason is most likely to keep oil from flooding the head and starving the sump. I would move my sending unit to a tee with the factory oil pressure sensor.
 

hooligan24

Thread starter
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903
Location
wa state
could the reduced flow be necessary because of the hydrolic lash adjusters? My brother just stopped by and asked what I was reading. After telling him what I was trying to figure out, he mentioned something about to much flow or pressure to the head could cause something called valve float.....or something like that. He also said oil restrictors have been around for many years in high rpm race engines. He then had to leave, so now I will be doing some searching on valve float and oil restrictors
 
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2,269
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NL, Canada
Its not uncommon to have a restrictor in the oil gallery that is supplying the cylinder head and valve train components. The restrictor not only reduces oil pressure to the cylinder head, but in doing so it increases pressure to the crankshaft journals and bearings where its needed most, and where it then flows back into the pan. The cylinders receive splash lubrication, and the valve train components need some pressurized oil to lubricate the valve stems and guides, etc, but not that much. If oil pressure at the head were too high, you would start seeing leaks develop in places like the valve seals and head gaskets. The OEM calculated how much pressure was needed in the cylinder head to lubricate those components adequately, and designed the restrictor - size and location - to ensure the entire system is properly lubricated. If you have a low oil pressure problem (38 psi is about right, or a tad high, for 3,000 rpm, but seems low for redline), there are many possible culprits but the restrictor wouldn't be one of them. Too little info to even make a guess on whether you have issue or what the culprit may be. -Spyder
 
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36,409
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ME
Originally Posted By: hooligan24
After telling him what I was trying to figure out, he mentioned something about to much flow or pressure to the head could cause something called valve float.....or something like that.
This is a pretty funny 2+2 conclusion. But valve float is when the springs can't keep up at redline and the valves don't close quickly enough. If you took your valve cover off and even idled the thing, you'd agree the top end of the motor got PLENTY of oil.
 
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35,624
Location
NY
It is to reduce the amount of oil into the heads, to avoid flooding the heads with oil and starving the lower end of the engine of oil. Flooding the heads with oil would cause a lot of problems.
 
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8,859
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Texas
The clearances in parts like rocker arms, rocker shafts, etc. are much bigger than the clearances in crank, rod, and cam bearings. The oil just flows freely out of them as fast as the pump can feed it... but all that's really needed is just a trickle to keep those parts wet with oil, not a gusher. Without some restriction to the valve gear in the head, ALL the oil would gush out up there and there wouldn't be enough pressure for the bearings... not to mention that the oil level in the pan would get low and the overhead area would fill up with oil. Just as a point of interest (or maybe not...) old American V8s had interesting ways of regulating flow to the valve gear in the heads. Chevy and Ford used oiling through the pushrods- very narrow passages, and the pressure pulses inside the hydraulic lifters provide intermittent "squirts" up each pushrod rather than a steady stream. Mopars used shaft-mounted rockers, with each hollow shaft connected to the oil galleries via drilled holes in the #4 cam bearing. However, the holes only line up once every other turn of the crank, so each cylinder head gets a brief shot of oil every other crank turn, keeping the pressure in the main and cam bearings high all the rest of the time. When you're pre-oiling a Mopar by spinning the oil pump with an electric drill (to prime everything after a rebuild, for example) and rotating the crank slowly by hand you can feel the drill "unload" and spin free when those holes line up and oil whooshes out one or the other rocker shafts.
 

hooligan24

Thread starter
Messages
903
Location
wa state
I found this video on valve float. very interesting visual. http://www.youtube.com/watch?v=_REQ1PUM0rY After doing some more reading, I have found the same answers about trying to keep the oil at the bottom end and to reduce windage when the oil is draining back to the pan. I have talked to a few guys online that have the same motor as I, but have their oil pressure sendors mounted in the stock location. they are seeing close to 70 psi at redline. One has theirs mounted between the pump and the oil filter and is seeing 80 psi at redline. I have my oil temp sensor mounted between the pump and filter. With my pressure sendor in the head, I see 75 psi at cold idle, and like mentioned before, 35-38psi during hot oil cruising on up to redline. I also found some post's by Darrel Cox Racing that mentioned the restrictor they install in their heads is to keep from overpumping the hydrolic lash adjusters and to keep the oil where it belongs, the bottom end. If valve float is when the valve rotates, my valve were designed to rotate...
Quote:
DESCRIPTION The valves are made of heat resistant steel. They have chrome plated stems to prevent scuffing. Viton rubber valve stem seals are integral with the spring seats. The valves have three-bead lock keepers to retain springs and to promote valve rotation.
 
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8,859
Location
Texas
Originally Posted By: hooligan24
If valve float is when the valve rotates, my valve were designed to rotate...
Valve "float" has nothing to do with rotation. Valve rotation is a GOOD thing, and virtually every engine made since the 30s has at least some mechanism to encourage some amount of valve rotation. Without it, valves would burn much more easily than they do. Flathead engines achieved rotation easily since the lobe could be made to "wipe" the tappet slightly off-center, causing the tappet to spin which then causes the valve to spin. Same for direct-acting OHC. Pushrod, overhead cam with rocker, and finger-follower OHC designs are a little trickier to get to rotate, but they all do it. Valve "float" is when the valve spring can't completely get the valve closed before the cam starts to lift the valve again, so it never fully closes. In that video you posted, you can see how the valve stem appears to "wobble" under the rocker tip. What's actually happening is that the valve is floating and not touching the rocker (gotta remember that this video isn't actually slow motion/high speed photography, its done by getting the shutter in sync with the rocker arm motion- the "wobble" is the valve coming up in a little different position every time.
 
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Messages
35,624
Location
NY
Originally Posted By: 440Magnum
Just as a point of interest (or maybe not...) old American V8s had interesting ways of regulating flow to the valve gear in the heads. Chevy and Ford used oiling through the pushrods- very narrow passages, and the pressure pulses inside the hydraulic lifters provide intermittent "squirts" up each pushrod rather than a steady stream. Mopars used shaft-mounted rockers, with each hollow shaft connected to the oil galleries via drilled holes in the #4 cam bearing. However, the holes only line up once every other turn of the crank, so each cylinder head gets a brief shot of oil every other crank turn, keeping the pressure in the main and cam bearings high all the rest of the time. When you're pre-oiling a Mopar by spinning the oil pump with an electric drill (to prime everything after a rebuild, for example) and rotating the crank slowly by hand you can feel the drill "unload" and spin free when those holes line up and oil whooshes out one or the other rocker shafts.
LOL reading this makes me realize how old I am. The system worked quite well back in the day. I still drive a Ford oiled that way, it works very well. LOL
 
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