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When I first start the car oil pressure is at 60psi and she sounds great, when she warms up a few minutes later oil pressure is at 20psi at idle and valves are tapping. I thought oil was suppose to thicken, 10w 30 is 10w cold 30w warm. Why is a couple of valves tapping when warm and will a straight weight fix the problem?

350 mild cam , and don't tell me to adjust the valves. :mad
 

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Multi-weight oil doesn't actually change viscosity. It has the properties (film strength) of multiple grades (viscosities). It will demonstrate the symptom of pressure change you describe as will all single viscosity oils. At the normal operating temperature of the oil, a multi-grade will meet the requirements of say a 5W or 50W what ever its range is. When cold, the same thing happens. A 30W cold is "thicker" than when at its operating temperature. Sounds more like you have a couple of lifters that are iffy when hot. Remember that they will also change characteristics when they warm up. 20psi is plenty for proper lifter operation at idle. If you change to a straight 30W it will probably quiet down the suspect lifters, for a while. It won't fix the internal wear in the lifter body. I'd also recheck the valve settings and make sure they are set properly. If you have been setting them at 1/2 a turn, you might try 3/4 turn and put the lifter internals at a different point in the body. (Get them out of the "wear area") Might work.
 

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Sorry 67, Bradleys reply is utterly accurate and correct. Do what he says. As much of a bummer as it is. SBC?? Then find an old valve cover and rip a slit out of it lengthwise that allows you to put your socket/ext in there but still sheilds the top of the pushrods from splashing oil. A bit of prep, yes, but the valve adjustment will be childs play.

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Gene Chaas
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67 SS 427
"Be big. Be a builder."
 
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I'm no petrochemical engineer, but that doesn't seem all correct. Multi weight oil certainly does change viscosity. Just not to the same degree that a straight weight oil would. Compare what comes out of your hot crankcase versus what you just took out of your freezer. Even a multi weight oil is thicker when it's cold than it will be at operating temp, it's just that when at operating temp it won't be nearly as thinned out as a straight weight oil would be.
 

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Sorry this is a little off subject. Is there and advantage to setting the valves with the engine running, or is it the same as setting them IO/EC? Also, can you set hydraulics with the engine running if you have roller rockers, if you loosened all of the set screws on one bank and set them one by one, would the lash hold until you set them and shut the engine down to lock the set screws?

Thanks,

Wes
 

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Larry, that's what I was trying to say. The multigrade viscosity will change from extreme cold to hot, but it will cover the range of say 10W to 40W if its 10W40 for example. The big advantae of multigrade is startup flow. A 10W30 will tend to fully supply the engine quicker than a straight 30W yet not break down when extremely hot, like a straight 10W would.

Like Pennzoil says -

. Why do we really need lighter viscosity oils?

Most late model engines were designed to use lighter viscosity oils compared to older models, which required a thicker film of oil to provide proper separation of parts, such as main bearings from the crankshaft. Oil passages were larger to accommodate these thicker oils. To take advantage of the fuel economy benefits of lighter viscosity oils (SAE 5W-30, SAE 10W-30), late model "low friction" engines are designed with smaller oil passages and film thickness requirements. Lighter viscosity oils also flow much more quickly at engine start-up especially in cold weather. Severe engine wear can result if oil fails to circulate rapidly to critical areas. Lighter viscosity oils also circulate more efficiently through the engine and remove heat faster.
 

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Larry, that's what I was trying to say. The multigrade viscosity will change from extreme cold to hot, but it will cover the range of say 10W to 40W if its 10W40 for example. The big advantae of multigrade is startup flow. A 10W30 will tend to fully supply the engine quicker than a straight 30W yet not break down when extremely hot, like a straight 10W would.

Like Pennzoil says -

. Why do we really need lighter viscosity oils?

Most late model engines were designed to use lighter viscosity oils compared to older models, which required a thicker film of oil to provide proper separation of parts, such as main bearings from the crankshaft. Oil passages were larger to accommodate these thicker oils. To take advantage of the fuel economy benefits of lighter viscosity oils (SAE 5W-30, SAE 10W-30), late model "low friction" engines are designed with smaller oil passages and film thickness requirements. Lighter viscosity oils also flow much more quickly at engine start-up especially in cold weather. Severe engine wear can result if oil fails to circulate rapidly to critical areas. Lighter viscosity oils also circulate more efficiently through the engine and remove heat faster.
 

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SAE 10W-30
Pours like a 10wt, sticks like a 30wt

That's the way I always understood it.

K

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64 2 Door HT 6-230 and a 'Glide (Arrived on the East Coast, Sitting at a lot in Atco NJ, hopefully undriven)
Formerly 71 ElcoTC Member #1155
 

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Here's a link to an article called:
More Than You Ever Wanted To Know About Motor Oil. http://rconcepts.com/beard/dragnet/drag/oilinfo.html

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67 Nova 385" daily driver - 12.1 @ 112
64 Chevelle Road Racer in the works
67 Nova Wagon under construction
 

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Wes,

Usually hydraulics are set with the engine running and hot (operating temp). You can set roller rockers the same as stamped...

Back off the nut until it taps, run it down (slowly) until it stops tapping, and then run it down another 1/4 or 1/2 turn. You can prob. get away with letting them go until the whole bank is done, but i usually tighten them down immediately after getting it set.

Another approach would be to go through once without locking them down, and then go back and one by one and re-adjust and then lock down. Some recommend adjusting twice to allow the lifter to "stabilize"

-Rich
 
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