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Not another oil pump question.

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dancrim

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My 65 BJ8 has seen a radical drop in pressure over the last year, and I don't drive it all that much. I did install a new rocker shaft to no avail. Before pulling the pump, I see Moss has the whole pump or just the gear set. I'd like to have some parts on hand + the pump and gears are on sale. What do you guys or gals think, is the Moss pump good or is there a better place to buy one....Thanks in advance and happy motoring.:fat:
 
Is it still as high when starting from cold. or is than number radically lower too?

You can buy a new oil pump, and you might even see a marginal increase in running pressure, but I doubt that's where your losses are.

Assuming that your oil filter, OE or aftermarket, is assembled correctly, the next bit of low-hanging fruit would be to determine if the bypass valve is seating fully.

You've said you already addressed the rockershaft, so next on the list are cam, rod and main bearings...
 
You didn't indicate the relative reduction in oil pressure you are experiencing. Another possibility to investigate is the escape of the timing chain tensioner piston/foot from its cylinder as a result of a stretched (ageing) chain. This will give you a drop in pressure but I don't expect it to be extreme.

Good Luck,
Ray (64BJ8P1)
 
Sorry for lack of details. I did check the bypass valve, cleaned and replaced spring. A year ago I ran 45 psi highway 20 idle, now I'm at 20 highway almost 0 idle hot. Cold engine is 45/25. I'll bet not more than 5000 miles
last year. I bought the car and never have done any motor work except for rocker arm replacement and new style oil filter (a long time ago). I am afraid I'm facing a motor rebuild (65000) miles on it and it sat for some 20 years. Company kicked me to the curb a couple of months age so I didn't want to start throwing money at it.
 
the next bit of low-hanging fruit would be to determine if the bypass valve is seating fully.

If it is you might also try shimming it when the engine is hot, see if the pressure will come up. May just be a tired spring???
 
Although the absence of a tensioner piston would bring down the oil pressure noticeably, it would depend on the oil used and engine operating temperature how far down. The numbers you have posted could fit within the depreciation of oil pressure as would so many other conditions. However, if your BJ8 engine has not been rebuilt, it is very possible that over the years the timing chain has stretched sufficiently to allow the piston foot to escape its bore. I would continue following Keoke's and any other easily addressed suggestions, before pulling the timing chain cover as that task will require pulling the grill and radiator, along with loosening the engine mounts and raising the engine to clear the cover. Although it is not a hard or parts-expensive job, it will require some effort.

Good luck,
Ray (64BJ8P1)
 
Have you checked your gauge against a known-good one? I had my gauge rebuilt and recalibrated a couple years ago and 'gained' over 15psi at idle.
 
Take the by pass valve apart , install a couple of washers , re assemble . Problem solved .
Also you can take the oil pump apart and ..lap... The cover plate with grinding paste on a piece of glass to make it smooth again .
 
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