35PSI - Means What

Okay, I know the bowels of the engine need attention and there's risk in it not getting proper attention now.

However,simple question regarding cold oil pressure at 35psi then dropping within 30 minutes of running to 5-10psi.

Are all the appropriate engine parts getting adequate lubrication when the pressure is at 35PSI?

If above answer be yes; then operating the tractor for 15-20 minutes with psi in the range of 20-35 causes no additional harm to engine? (About 20 minutes at the time is all I need of tractor time in the garden most of the time.)

(quoted from post at 00:01:38 09/30/12) Okay, I know the bowels of the engine need attention and there's risk in it not getting proper attention now.

However,simple question regarding cold oil pressure at 35psi then dropping within 30 minutes of running to 5-10psi.

Are all the appropriate engine parts getting adequate lubrication when the pressure is at 35PSI?

If above answer be yes; then operating the tractor for 15-20 minutes with psi in the range of 20-35 causes no additional harm to engine? (About 20 minutes at the time is all I need of tractor time in the garden most of the time.)

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Your oil pressure is completely normal, run it!

Those numbers are what 95% of those old tractors ran at. If you want higher numbers switch to a straight weight oil or a heavier oil

equeen........congratulations you have just found the effects of VISCOSITY. Cold oil is thicker than HOT oil. Even water has a viscosity factor; cold is ICE and HOT is steam. Isn't that amazing. You need to be concerned about HOT oil pressure; it is what keeps the bearings from rubbing on the crankshaft journals. It should be intuitively obvious that metal to metal rubbing can be "expensive". The N-Oil is pressure relived to 35psi max when cold. Oil pressure is a combination of oil weight and oil pump efficiency. .........oily Dell

The main thing that determines oil pressure is the clearance in the bearings. Too much clearance and I don't care what oil you use there will be no pressure. Granted you need a good pump to start with but the best pump in the world will not create pressure without the resistrictions from the bearing clearance.

I ran a 1949 8N with 5 pounds of oil pressure when hot for 20+ years and worked it hard. I bush hogged and plowed and mowed grass for hours. When I finally tore it down and rebuilt the engine It showed no undo wear. These low rpm machine will run a long time as long as the bears etc. get some oil even if it is just a little. Just change the oil around every 50 hours of operation and it will be good for a long time.

My 9N runs just like that with 20/50 W in summer.

Been that way since I've owned it, 1989.

It don't make knocks or taps either.

(quoted from post at 13:09:43 09/29/12)
The main thing that determines oil pressure is the clearance in the bearings. Too much clearance and I don't care what oil you use there will be no pressure. Granted you need a good pump to start with but the best pump in the world will not create pressure without the resistrictions from the bearing clearance.

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Precisely. And I don't care if you have 80 PSI pump oil pressure that oil pressure won't keep the journals clear of the bearings if the clearances are too wide. The journal is held off the bearing surface by a [b:2036184fa0][i:2036184fa0]localized pressure differential [/i:2036184fa0][/b:2036184fa0] inside the bearing shell that is orders of magnitude greater than pump oil pressure - well up into the thousands of pounds. That differential comes from the formation of a hydro-dynamic "wedge" of very high pressure oil (red area in the drawing) opposite the load on the crankshaft. It is produced by the journal surface dragging oil around the bearings as it rotates and compressing it in the constricted clearance opposite the load. Too much bearing clearance and that wedge won't form and the journal is forced down onto the bearing surface by the load. It is this hydro-dynamic phenomenon that allows a splash lubed lawn mower engine to maintain a bearing oil film with ZERO pump oil pressure. The three factors that affect the formation of that wedge are:
[list:2036184fa0][*:2036184fa0]Bearing clearance[*:2036184fa0]Oil viscosity[*:2036184fa0]Surface speed of the journal[/list:u:2036184fa0]Pump oil pressure has virtually nothing to do with it.

TOH

35 cold and 10 hot is still acceptable..


soundguy

Okay, another question or two.

Seems that the tube from the oil guage runs to a plug near the rear of the engine block.

I'm guessing that the the "plug/fitting" simply opens up inside the oil chamber/cavity in the engine block thus registering the oil pressure as it exists in the oil pan, oil cavity in engine block, oil cavity in head, oil cavity in oil filter container???

In other words the oil pressure as it exists in the oil, against any metal surfaces, air spaces, whatever in the oil cavities wherever located inside or outside - but part of engine oil cavities????

(quoted from post at 16:01:01 09/29/12) Okay, another question or two.

Seems that the tube from the oil guage runs to a plug near the rear of the engine block.

I'm guessing that the the "plug/fitting" simply opens up inside the oil chamber/cavity in the engine block thus registering the oil pressure as it exists in the oil pan, oil cavity in engine block, oil cavity in head, oil cavity in oil filter container???

In other words the oil pressure as it exists in the oil, against any metal surfaces, air spaces, whatever in the oil cavities wherever located inside or outside - but part of engine oil cavities????

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The fittimg is installed in the main oil gallery that runs front to rear alongside the camshaft. The pressure shown is what is being delivered to the main and rod bearings.

TOH

equeen........you have the oil flow BASSACKWARDS......oil flows from the oil pump, which is part of the #1 crankshaft bearing at the front of the engine, thru the camshaft gallys and out the BRASS "T" at the back of the engine where one side of the oil flow dead ends into the dashboard oil pressure gauge. The OTHER leg of the brass "T" returns the oil flow THRU the oil filter on the left side of the engine OUT thru the BOTTOM of the oil filter canister around to the governor CUP where it leaks INSIDE the front of the engine camshaft cover plate. Yer I&T FO-4 has a great pictorial of engine oil flow. (buy-1, $25, cheap) ........respectfully, oily Dell

Too many manuals, too little time, too lazy to look. However, Fig. F027 appears to be the Oil circuit diagram of which you write.

Your writing was better than the picture.

And, yes, I stay bassackwards lots of the time.

Thanks for your very helpful response.

How MUCH oil pressure you have is not nearly as important as the fact that you HAVE oil pressure.

(quoted from post at 01:06:13 09/30/12) How MUCH oil pressure you have is not nearly as important as the fact that you HAVE oil pressure.

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"I'm guessing that the the "plug/fitting" simply opens up inside the oil chamber/cavity in the engine block thus registering the oil pressure as it exists in the oil pan, oil cavity in engine block, oil cavity in head, oil cavity in oil filter container???"

Yes, queen, your engine will either seize or blow up if oil pan or crankcase pressure drops much below 10 PSIG. Much more than 10 will probably blow the oil filler cap off. It is truly a fine line here that we walk. Serious business. You should probably pull the engine immediately, without further delay or useless testing & eyeball the internal/deepest guts to see for yourself, just what may be amiss. You shouldn't even wait until sunrise.....no telling what could happen overnight!

I've removed the plug from the oil pan. That should relieve the oil pan pressure enough for tonight.

But, to be safe I'll jiggle the dipstick a bit and remove the cap from the oil fill tube.

Thanks.

Plug the line at the "T" at the rear of the block either at the "T" or oil filter can. Crank the engine and you will get your true oil pressure reading. If it is high then you are loosing pressure due to engine ware. If its low the there is a possiblity of weak oil pump or leaking pick up tube. This will point you to your repair needs.

(quoted from post at 22:37:40 09/29/12) Plug the line at the "T" at the rear of the block either at the "T" or oil filter can. Crank the engine and you will get your true oil pressure reading. If it is high then you are loosing pressure due to engine ware. If its low the there is a possiblity of weak oil pump or leaking pick up tube. This will point you to your repair needs.

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"Plug the line at the "T" at the rear of the block either at the "T" or oil filter can. Crank the engine and you will get your true oil pressure reading. If it is high then you are loosing pressure due to engine ware." Your statements do not make sense to me. Would you be so kind as to expand /clarify your reasoning?

You should be fine to run it, what weight of oil are you running?

I was running (about 1 hour) NAPA 30.

However, now that I've removed the oil pan drain plug - the engine has no oil.

Once I get the drain plug "welded up" I shall re-fill the engine with Pennzoil 20W50 and see if I can get a few more points at the hot stage.