Re: Oil pressure at 10 psi

Posted by HH56 On 2021/1/23 18:37:59
You said it is a 288 block so engine would have to be 1948 or later. A couple of things to check. The bottom port on the drivers side is direct from the oil pump and should be at approx 40-50 lbs at driving speed. At idle speed it can get down to approx 10 lbs but much lower than that and the idiot light would go on in the 51 and later models that had that indicator light. The upper port on the drivers side is the inlet to the oil lifter gallery and is fed via a pigtail from the bottom port. Depending on which port the gauge is testing there could be a difference if a couple of conditions are present.

If the replaced oil pump was NOS then probably not the issue but if it was rebuilt and a wrong gasket was used, clearance between rotors and end plate will be too high and the pump cannot develop the proper pressure. Several have reported finding ordinary gasket paper used but the original was almost like tissue paper. I believe it was Ross who said he makes his gasket out of "onion skin" typing paper.

There are plugs at each end of the lifter gallery. According to some service articles, if the back one is missing the oil cannot escape but if the front one is missing oil could be freely flowing into the timing chain area which could lower pressure.

On some blocks with the early versions of the filter the supply coming from the bottom port had an orifice in the brass block to restrict flow to the filter. If the block is reversed and the orifice is on the lifter gallery side and the gauge is plumbed to the upper port it could read low. The same low reading could be present if there is no restriction in the brass block (or in the oil filter assy itself with later filters) and oil is just freely being dumped into the pan. That would also have a low reading if the gauge is in the upper port and possibly also at the lower port.

One other thing being assumed is with the rebuilt engine the oil pan was cleaned out so no sludge is present and also it had oil in it or if not, was stored in such a way that no furry critters could have built a nest in the pan and obstructed the oil pickup screen.

Attach file:



jpg  oil paths.jpg (120.66 KB)
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jpg  plug.jpg (113.14 KB)
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jpg  pump.jpg (41.49 KB)
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