High Oil Pressure Reading

[8N_John]

I just noticed that the oil pressure reading on an 8N I recently bought is always maxed out (above 50psi). This is true when I start and after running for awhile. Oil level is normal. Is this just a bad gauge or it could result from another problem???

 

[Nasty135]

8N_John, With a pegged oil pressure gauge during start up and settling back after warm up,It could be a normal condition and it could a slightly sensitive gauge.
Since you say recently bought I'm assuming you have not changed the oil yet? When you change the oil and put in your fresh oil? if you notice a difference in the oil pressure maybe the original owner had thicker oil in it for the summer months? Or he could be hiding something (worn rings)...
But if it runs good and doesn't smoke its probably nothing to be concerned about /forums/images/graemlins/cool.gif
Just read your post in lubricant's? I think you have changed your oil ,If its different than when you first got it the original owner probably had a different weight oil or it was old oil?? Anyhow the fact that after warm up it comes down to normal tells me that there is good oil press and not too much oil pressure ,so don't worry about it...

 

[Soundguy]

If it is the OEM gauge.. I'd go buy a 9$ cheapy sunpro just to verify the readings.. the old gauges are only acurate to within a few pounds anyway, at best.. and at worst.. I've seen reading all over the place that were not correct.. it is a 50+ year old gauge..

Also.. As the other poster said.. the previous owner may be running 40 or 50w oil in it to boost hot idle pressure. Verify this by your own oil change.. which I consider mandatory before I even run anything I buy anyway.

One other option may be that the previous owner ( or 50 years of gunk and use) may have dinked with the oil pressure relief valve.

On the front of the engine, top right side.. to the right of the distribuitor ( if a FRONT MOUNT ) or to the right of the water pump.. you will notice one of the bolts is much larger than the others.. this is a cap that has a spring and plunger under it. If the plunger is stuck shut, or if the spring has been stretched.. or a bigger spring put in.. the relief will not function, and your oil pressure will go up / stay up.. if the oil pump and beaing tolerances allow it. 50psi is too hogh.. you don't eally want anything over 40's, even after a rebuild.. relief should have been set somewhere between 34 and 45 from the factory based on spring length and tension. ( yes the plunger is sopposed to have a flat spot on it ). Some people with slightly low oil pressure will stretch their spring to get more pressure.. later on they rebuild the oil pump and or use heavier oil, and never remember to rplace the spring... Check this.. ot may be your problem if the new oil and new gauge don't work out.

Soundguy

 

[8N_John]

Thanks for the info. I will try a new oil pressure gauge even though the one I have looks fairly new. The oil pressure does not go down after running awhile. I recently changed the oil...put in 30WT.

How would I adjust and calibrate the oil relief valve? Is it safe to unscrew the bolt?

 

[btolle]

My last 8N oil press. gauge suddenly dropped one day. I changed oil but it still would only barely register when cold and was at zero when hot. Since it sounded normal I didn't worry about it. A couple of months later it started working correctly again.

I suspect some trash had gotten in the line from the engine to the gauge and it finally broke loose. You might want to take the line off and runs some carb cleaner through it to get 50+ years of gunk out of it.

The best thing I did was buy an IT service manual for my 8N. Just about anything you want to know is in the manual including how to completely rebuild it. I was amazed at how much information was in what I thought was a pretty 'thin' manual.

Bill Tolle

 

[Soundguy]

Even if the gauge looks new.. spend the 9 bucks for piece of mind. Luckily that 8n is ALL good old sae.. and you shoul find the adapters needed for it in the sunpro gauge pack.

While I agree with the other poster that a sudden drop in pressure can be a clogged line.. a rise in pressure is not a usual symptom.. however.. when you do change the gauge.. leave the fitting a tad loose and throw a rag over it.. crank the engine over or start it at low idle till you get the air bled out of it... Air bubbles up at the gauge can cause weird readings too.

Once you repalce the gauge, and it is still high. Kill the engine and go take a look at that plunger / spring. While I think the FO-4 may give the inch pounds and length of the spring.. I think an old one is gonna be a gamble on getting it adjusted.. however a new spring is cheap.. still.. if you feel up to it.. you might try bending or shortening it a loop or so.. If you start it up and have no oil pressure, you have lost prime, and / or the spring is too loose and letting all the oil bypass. Stretch the spring back out or replace to account for the lowered oil pressure. If it did loose its prime, get some heavy oil.. egen gear oil.. anything that is thick.. even stp motor addative.. pour it down the relief hole till it is full.. slap the spring and plunger and cap back on super fast, and then get that engine cranking over to get the pump primed. As you may have guessed, the oil relief setup is above the oil pump, and dribbling oil into it fills the gearing. Loss of prime while dinking with the plunger / spring is not common.. but not unheard of either. Let me see if I have some pics for you.

Soundguy

 

[Soundguy]

Ok.. that first pic shows the manual's info about the spring and plunger - part numbers.

Also.. I lied to you.. the plug is actuall to the left of the water pump and under it.. but it is to the right of the front mounted distribuitor on the timing cover. For a side mounted distribuitor, it will still be there.. just the timing cover will be a tad different. Sorry.. Been a while since I dinked with the oil pressure valve.. I knew it was on front at least!

Next pic shows some other shots.

Soundguy

 

[Soundguy]

next pic

Soundguy