Curiosity killed the oil pressure?

[Mr. T. Minnesota]

Forum members,
I was looking for more consistent oil pressure on an 8N front mount and did not get what I wanted! I got a new spring and replaced the old one which looked worn on the inside. The plunger had a flat spot about 3/16ths of an inch in area. Started her up and had less pressure than before. Is it possible to resurface the dome shaped plunger or should I just get the $21.00 new plunger? I have a metal lathe and/or drill press to resurface it. Are both surfaces made of the same metal or is the plunger softer? Any info is appreciated!!
Mr. T. Minnesota
 

[souNdguy]

plunger SHOULD have a flat spot.

is the new spring SHORTER than the old one? if so.. there's where some of the oil pressure went..

post back
 

[Mr. T. Minnesota]

SG,
The flat spot is on one side of the dome not at the end!! Shouldn't the dome be a complete dome except at the end/top? Am wondering why the dome is flattened on one side?? The guy that overhauled the engine had not replaced the spring and plunger. Hope I explained it a little better. Appreciate any more thoughts!!
Thanks,
Mr. T. Minnesota
 

[Badger bob]

On my sons 2n i removed the flat spot and it went from 20 at start up to 60! but still 3 lb at warm idel. so i went back to the orignal one . bob
 

[souNdguy]

and yet...my answer hasn't changed any....

at this point I'll assume you are answer shopping, waiting for one you want to hear.

so I'll leave it at that.

have a goodun'
 

[Bulldozer]

Looked at the plunger on my 49N that is totally torn apart.

The plunger has a flat spot on only one side.

Had zero oil pressure when the engine was torn down.
 

[Bulldozer]

OK ,if the plunger is supposed to have a flat spot what is the orientation in the hole?

The flat spot appears to be wear surface!
 

[mhb@ufe]

The flat spot is there to allow oil flow at all times. The orientation doesn't matter. What is the problem with your oil pressure?

Mark
 

[Mr. T. Minnesota]

SG,
As to the spring length, it is the same. The tension seemed close to the same also. The spring said it was made in the USA too. The previous pressure was about 25 psi at a cold start and tapered off to about 10 psi. Now it does not get above 20 psi at a cold start and have not run it long enough to determine the hot reading. I do not plan to put in the old spring because the spring was worn where it contacted the plunger as it did on my 2N. A broken spring is not good news.
Thanks for the replies!
Mr. T. Minnesota
 

[souNdguy]

go rethink that one for a moment see if it comes to ua.

think about a seat and a free floating plunger with a flat on one side of the needle face. what do you expect happens in that gap.. no matter where it is? ?
 

[souNdguy]

as a test.. stretch the new one a tad and see what happens...
 

[mhb@ufe]

The relief valve will set the high pressure at start up but has very little to do with amount the pressure drops when warmed up. That is more to do with bearing clearance and condition of the oil pump itself. If changing the spring lowered your cold start oil pressure the new spring doesn't have as much tension as the old one. I would expect your hot oil pressure to be about the same as it was with the old spring.

Mark
 

[Bulldozer]

My theory is the plugs were fouled so badly, raw gas entered into the oil sump and thined out the oil so much the pump gears would not pick up the oil from the sump.
 

[Bulldozer]

That's a relief don't have to get a replacement plunger, one less thing!
 

[souNdguy]

the flat spot discover happens almost as much as people asking if they can use a roto tiller on their 8n.