1929 Chrysler - Oil Pressure

[bypass]

Hi everyone.. 

 

I have a 1929 chrysler series 65 (engine silver dome head). When the engine is cold the oil pressure reaches 30. Then gets warmer and reaches 20 and then keeps 10. into idle reaches 5....

 

I was using a 20w-50...then I changed to 20w-40, and now I´m using a 30W (moderate detergent monograde) and the problem remains....the oil pressure drops when the engine warm.... I´m killing the engine if I don´t do anything....!Someone knows where I can raise the pressure oil? or the the problem is in the oil that I use?. I hear many times that this engines must use non detergent oil...here is the problem?

 

 

Thanks everyone!

[vermontboy]

From memory that is probably within spec for a late 20's early 30's engine. Someone will come along who's memory is perhaps better than mine.

[Taylormade]

A lot of this is related to the overall condition of the engine.  Is it badly worn, is the oil pump in spec, is the pressure relief valve set up correctly?  I’d take a look at the oil pump to start, and then go from there.

[keiser31]

15psi oil pressure at idle is adequate. A little more is good.

Edited August 13, 2018 by keiser31 (see edit history)

[ArticiferTom]

Verify your gage is good . Build up in line to will give poor reading . For less then 20 buck ebay has direct screw in gage for motor . Use to set relief valve also . You are also dropping wt of oil going 50  to 40 to 30 . The 20 w,  is what it acts when cold . The only way to increase pressure is with pump . System is designed to bleed off extra unneeded pressure .

[ArticiferTom]

My '31 Plymouth 4 drops low on idle when hot . Book says between 30 and 40 when driving 30MPH with hot engine .

[bypass]

I've read this question is common to other cars of this date! The question is why the pressure only falls when the engine is warm.  In cold is fine. The oil is monograde and is new!  That´s because the engine in hot state expands?

 

When I changed the oil 20w-50 to 20w40 and now to 30w I noticed that the pan start  have some mud inside (was completly clean at beginning)...I supose that´s because the oil pressure drops....!This engine don´t have filter oil...but this one thing that I want set up, very soon. I already have the canister/filter oil..

[Gunsmoke]

My '31 Chevrolet straight 6 (overhead valves) runs nicely and normal on about 6-7 lbs oil pressure when warmed up. I don't know what was expected as " normal running pressure" for the Chrysler, but most of these old engines used a whole batch of means to get oil to things, mine uses dippers on rod caps to splash oil around bottom end, oil pump just pushes oil up to rocker arm shafts where it flows out by gravity and down through various holes to oil bearings, pushrods, etc. Not very sophisticated by today's standards, but still running smoothly after nearly 90 years. 

Edited August 13, 2018 by Gunsmoke (see edit history)

[bypass]

"Book says between 30 and 40 when driving 30MPH with hot engine"    mine reachs 10 when is hot.....BIG Problem....

[fraso]

My Motor Manual only goes back to 1935 but I don't think that 1929 cars were spec'd much differently.  The warm weather (above +32°F) specified viscosity for 1935 cars was SAE 20 with an oil pressure of 45 psi @ 30 mph.  If you're only getting 10 psi at 30 mph with fully warm SAE 30, then you've likely got some mechanical issues to address.

 

It is natural for engine oil to become thinner (less viscous) with increasing temperature.  The oil pressure you see on your gauge is a reflection of the oil's flow and downstream flow resistance.  Before doing anything else, I would double check the oil pressure with an oil pressure gauge of known accuracy.  It could just be that your gauge is way out of calibration.  See Engine Wear.

[PFitz]

As mentioned, worn bearings and pump will reduce oil psi. Oil pump gears and housing wear on their ends allowing oil to leak back past the gears and not be forced through to the bearings.

 

One other thing that is often missed is the oil pressure relief valve spring will weaken with age, and/or, the valve and it's seat get cruddy. Either can cause an excess of bypassing oil and drop the pressure. Sometimes all you need is to remove the valve and spring, clean the valve and it's seat, then stretch the spring a bit to lengthen it back more toward original tension. 

 

Paul

Edited August 13, 2018 by PFitz (see edit history)

[C Carl]

Hi bypass ! 

First, I am real happy to see a young (almost 40 years younger than I am), guy playing with the kind of cars I have loved since I was about 3 years old ! 

 

Next : how much blue smoke does your car blow, and when. Cold ?  Hot ?  On throttle.?  Off throttle ?  Hard acceleration ?  Downhill using engine braking.?

 

And now, since you have been using detergent oil, keep on doing so. If you have some oil flow problems, make sure what oil you ARE using is the very best. Use one of the better FULL SYNTHETIC  OIL, l recommend Amsoil because I use it, but for now just make sure it is FULL SYNTHETIC . And go back to the 20W/50. Not Castro. 

 

And last, for now, where do you live ? There might be a member close to you who can help.

 

Here is a backup oil pressure gage that I feel is a very good idea, along with a backup temp gage. These are essential for a car which travels far from home. This one does. It is a 1927 Cadillac. 

 

 

[Mikefit]

Here is a good Rule O Thumb for a full pressure oil system you need 10# of pressure for every 1000 rpm. 

[ArticiferTom]

I'm afraid it is time to consider pump rebuild . If you 've established a good gage . Setting relief is easy and you can do when oil is cold and pressure at it's highest . But it a max only adjustment and does not affect the lower numbers or where the range is . It bleeds off fluid to lower the pressure .

[Spinneyhill]

Pretty much all liquids thin (lose viscosity) with increasing temperature. That is part of the reason you see an oil designation such as 20W-50. It behaves like a SAE 20 oil when cold (think of the W meaning Winter) but like a SAE 50 oil when hot. You can read about viscosity in Richard Widman's papers.

 

Pretty much everything you have read or heard about non-detergent oil is rubbish. Keep away from it. You will fill the inside of the engine up with muck, everywhere, inside the oil passages, in the pressure relief valve, in the pistons, in the ring grooves, in the valve gear, not to mention the thick layer in the bottom of the sump. Additives are used for many purposes, one of the most important being to slow the progression of the oil to sludge due to shear while in use. Your manual will tell you to change the oil at what we view today as very short intervals: that is because the oil is turning to sludge (which doesn't lubricate much), as well as breaking down and losing lubrication properties. Just because they had no additives in 1929 doesn't mean you should do the same thing. Oils of today are far, far better.

 

What is the history of your car? Have you had the sump off for a clean and inspection of the inside of the crank case? If the engine has high miles it might already be full of muck, with diminished oil passages restricting oil flow. Certainly your oil pressures sounds a little low so perhaps it is time to look at the oiling system - the cleanliness of the engine, the pressure relief valve and the pump to start. You might consider a 15W-50 oil (get the first number down so you get better oiling on start-up). As Carl says, synthetic oil is best - wear tests show ANY synthetic oil is better than ALL mineral oils at reducing wear.

 

As an aside, if the oil pressure is a bit low, what is the rest of the engine like? Are the compressions near the factor spec.?

 

For your information, I use Penrite HPR5, an API CI-4 rated diesel oil in SAE 5W--40 in my 1930 Dodge Brothers Eight.

[Vintageben]

I just posted this in the Chrysler section but for what it is worth here is what my Chrysler 65 Instruction book says. Also my engine used to great oil pressure but was stuffed I’m guessing there were galleries block some where. 

[Grimy]

Have you cleaned the oil pump pickup/intake screen during your ownership?

[broker-len]

have a 32 PA     Plymouth     had it for 40 years       low oil pressure    motor rebuilt  mains pored not sure of cam bearings    still low     pulled oil pump got new gears     weighting for them   do not think it is the gage but that is next   was told thick oil is not the answer and I am a believer is 10w30     modern oil use pennsoil

Edited August 14, 2018 by broker-len (see edit history)

[maok]

Things you can try;

 

1. adjust the oil pressure relief valve,

2. pull the oil pan and clean out the oil pump pick up filter/screen

3 rebuild the oil pump,

4. do what I am doing, rebuilding another motor...lol

[ArticiferTom]

Maok's number 1 is also the easiest . You do not need to drain oil . Just remove acorn cap cover . It may have couple oz's. of oil behind . Remove cotter pin or wire ,after counting exposed threads of adjustment screw . Remove same and piston pin behind it clean , check hole and reinstall .

Edited August 14, 2018 by ArticiferTom
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