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(1) 2 »

oil pressure on '49 Custom 8
#1
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prentice672
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I'm only getting 30 psi at normal cruise speeds on my '49 Custom 8. I guess it's supposed to be 50 psi. Should I worry that it's bearings or a bad oil pump. Any chance it's just the gauge?

Posted on: 2016/9/30 22:18
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Re: oil pressure on '49 Custom 8
#2
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HH56
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Specs say 50psi for the 356 at driving speed.

Gauges are electric so it could be a faulty reading. Many have added a mechanical gauge to serve as a backup and to double check the electric. Some have used a regular auto accessory type gauge with a long tube connection and mounted it discreetly somewhere. Others have used a small direct reading dial type gauge plumbed directly into a port. McMaster has a nice assortment of small 1-2" face dial gauges.

I'm sure you are aware the mechanical possibilities for low pressure are several but here are the obvious ones: the spring in the pressure relief valve on the pump could have weakened and is allowing it to dump "excess" pressure too early; the engine could be well worn and excessive loss at the bearings comes into play as well as one remote but still very possible cause. Prewar 356 engines had a valve at the end of the main gallery to oil the timing chain. Packard called it a jiggle pin. The hole the pin fit into would wear and allow the pin to fall out resulting in a large flow of oil to the timing chain and low pressure resulted. Starting in 42 and until the end of 356 production the engines had a spring loaded piston valve instead of the pin. It was found that sludge could cause that piston valve to stick open with the same result of dumping oil onto the timing chain and the low pressure. If the engine is original then it should have the piston but if it was changed then the jiggle pin is still a possibility.

Posted on: 2016/10/1 9:51
Howard
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Re: oil pressure on '49 Custom 8
#3
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Wesley Boyer
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Also what weight of oil are you using and brand. Did you just notice this after the last oil change?
Things to think about.
Wes

Posted on: 2016/10/1 10:01
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Re: oil pressure on '49 Custom 8
#4
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prentice672
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I got the service bulletin and in it they describe a simple test of the sending unit and my unit failed the test. So I'm just going to replace it and hopefully I'll get the correct pressure. I just wish I didn't have to go to Kanter or Merritt. Thanks for everyone's suggestions.

Posted on: 2016/10/2 10:19
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Re: oil pressure on '49 Custom 8
#5
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John Iaccino
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If the spring in the oil pump is weak, try putting a couple of washers in to put more tension on the spring. Quick fix until you find a rebuilt pump.

Posted on: 2016/10/3 4:32
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Re: oil pressure on '49 Custom 8
#6
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Owen_Dyneto
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A weak spring on the oil pump pressure relief valve is NOT an indicator that the oil pump needs rebuilding.

Posted on: 2016/10/3 9:59
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Re: oil pressure on '49 Custom 8
#7
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prentice672
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I got a new oil pressure sending unit and it still indicates the same, around 35 psi, or just to the left of the "40" mark on the gauge. I performed the same test on the new unit as I did the old and it seems to pass the test, i.e. the needle does not go to the extreme limit.
I then removed the pressure relief valve and cleaned up the piston and tried to clean up the bore as best I could. I ran up the engine and it still reads about the same. I'm thinking a new oil pump(?)

Posted on: 2016/10/10 23:12
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Re: oil pressure on '49 Custom 8
#8
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fredkanter
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I see you express regret you have to go to us or Max Merritt, I'd suggest you go to your local Packard dealer or walk the 20 miles of Hershey. And when you need a fender, exhaust valve or door handle do the same. In fact all Packard owners should boycott both of us, that'll serve us right!!!

Posted on: 2016/10/10 23:43
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Re: oil pressure on '49 Custom 8
#9
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Owen_Dyneto
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I'm thinking a new oil pump(?)

It's far more likely to be worn engine bearings than a worn oil pump. But it would be worthwhile to remove the cover plate from the oil pump and if it has a wear pattern from the gear teeth, have the resurfaced and reinstall with as thin a gasket as you can make (thicker the gasket, the lower the output pressure).

Posted on: 2016/10/11 6:38
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Re: oil pressure on '49 Custom 8
#10
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Dave Kenney
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I wouldn't worry about the oil pressure in this range unless you use the car as a daily driver. I drove my 1947 with about the same oil pressure as your car for many miles over several years . Many cars of this era ,before and after, operated on far less pressure .There is enough oil pressure to protect the bearings and internal parts in my opinion. Likely it has worn bearings as O.D. mentioned but if they are not making noise a car will run a long time without repair especially if oil is changed regularly. Regrinding a 356 CID crankshaft let alone rebuilding the engine to gain 20PSI is not for the faint of wallet either and may not be worth the expense unless you plan on doing some long distance driving over the course of a few years . Just my thoughts which others may disagree with.

Posted on: 2016/10/11 10:36
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Dave
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