Too much oil pressure ?

[Don G]

I'm hoping you guys can help me. Is my oil pressure too high and if so what can I do about it ?

Oil pressure at running temperature is: 1k rpm 25psi, at 3k it's 75psi, at 4k and above it's between 90 and 100 psi.

Engine is newly built with about 1500 miles on it now. It is a 2.2 case and cylinders with s pistons, e cams, and a 2.4 crank and rods. The oil bypass mod was done and the upgraded 4 rib pump was put in. Using BradPenn 20/50 in it after the break in. Engine runs great and is nice and cool but with all that pressure I'm worried. What do you think ?

Thanks in advance,
Don

[4sd911]

I guess first you should check the pressure independently with an different gauge to make sure your gauge and sender is reading correct.

[Walt Fricke]

If you use a 5 bar sender with a 10 bar gauge you will have gauge readings of twice what actual is.

About the time of the SCs Porsche switched to 5 bar gauges and senders.

[HawgRyder]

Roughly 15lbs = 1 bar.
So...it looks like you are just a little high at 1K ....but not dangerously so.
At 3K you are getting 5 bar ... this seems way too high.
Are you sure your bypass and pressure relief pistons are not stuck?
If the mod was done to the block...were the holes de-burred?
These can be checked from under the engine...be careful...they do drop oil when taken out (don't have your head under them when you first remove the caps)....LOL
Bob

[Steve@Rennsport]

Originally Posted by Don G

Oil pressure at running temperature is: 1k rpm 25psi, at 3k it's 75psi, at 4k and above it's between 90 and 100 psi.

Don,

Specifically, what temperatures are you seeing?

[Don G]

Steve,
Runs 180 when up to temp with outside 85 or below which was where the thermostat opened when I tested it during the build, got up to 100 outside and the temp went up to 190-200 but never over 200. What were you thinking ?
Don

[Don G]

Walt,
The Gage is the original Gage in a 71. The sender was new, purchased here. How can I test ?
Don

[Walt Fricke]

The sensor will say what it is. It is stamped into the hexagonal base part, below the big fat bell part. Should say 10 bar or 5 bar, and/or perhaps 150 psi or 75 or 100 psi. VDO's website may have a picture showing an example, and should say what flavors the senders come in.

You want the 10 bar sender. Would the seller have known what to ask when you bought it?

[Don G]

Bob,
No I'm not sure they are not stuck. If I take them out how do you tell if they have been/or are stuck ?

Walt,
Good question, wish I had asked it. Not sure the seller would have known. There's no easy way to see the markings with the engine in the car is there ?

Thanks for the help guys.

[HawgRyder]

If you remove the pistons...(don't mix up any parts ) and check the sides of the pistons to see if there are any "gaulling"..SP?) marks on them.
They should slide up and down very easily...I check them by pushing them up with a wooden dowel and letting them slide down under their own weight.
Sometimes the oil will not let them slide down...but you will feel the drag as you push up (it should be very free).
Bob

[Walt Fricke]

Don

The oil pressure sender is readily accessible, since it is located just to the lower right of the fan housing. If you have AC in the way, easy to move that temporarily out of the way.

Well, that is if you have a fitting in the right cam oil line at that location to receive the pressure sender.

If it is there, you ought to be able to clean it up to see if you can see the markings, and if not, to start unscrewing it until you can see them or just take it off entirely to look.

The other place it might be would be on the right rear of the engine case up top, to the left of the thermostat. This is where, on later motors, the idiot light sender is located. It also happens to be the top end of the oil passage where the main pressure setting piston is.

As long as you have carbs or MFI or EFI,that part of the motor also ought to be easy to access to pull the sender. And you can stick a rod down the hole to see if you can push the piston down against the spring.

You probably know that the oil pressure control modification includes two new and different pistons (the old ones had holes in their sides, the new ones have a sort of recessed ring around them below the top and no holes in the sides. Also a different (longer but softer) spring in the main system, along with a tube inside the spring to keep it from bending when compressed. If any of this was not done, but the oil pressure mod (which sends excess pressure/oil back into the pump intake instead of the case sump) was done, you will have problems. Hard to imagine any one screwing this up, but worth checking - if you have the right sender.

Oil pressure senders are relatively easy to test if you have some tools and stuff. First off, you can check the resistance between the terninal and the body of the sender (ground). If you have infinite resistance, something is broken inside. It should show some resistance. The next test is to build a jig so you can screw the sender into a block, and attach an air hose male end to the jig, with things drilled so they connect. Then you can feed air (with an air pressure regulator and gauge) in, and measure the ohms output at various pressures. Without getting into exact units, the resistance should climb with the pressure, with the highest resistance with the highest pressure the gauge is rated for.

But I doubt your problem is a gauge which reads too high. These gauges usually fail because a wire inside breaks (infinite resistance) or the resistance windings inside get worn by the slider and break, so you have normal readings up to a point, and then infinite resistance.after the slider passes over the break.

[Don G]

Walt,

Thanks for the explanation, mine is in the back by the thermostat. I have carbs (pmo's).

I've developed the following plan based on what you guys have said.

1. Remove the sender (which was new or supposed to be new), examine it to see what bar sender it is.
2. Attach an external pressure gauge and see what it says. Have a friend who has a gauge, just need to come up with a way to interface it with the case.
3. If 1 and 2 don't give me the answer, then on to removing the pressure relief pistons too see if they are the problem.

I'll report back on the outcome.

Thanks for your (and everybody else's) help.

Don

[4sd911]

Remember do not remove the sender while the block it mounts to is still on the case, remove the block first then remove the sender from the block in a vise. Trying to do this on the engine can crack or break the case, the mag case is very delicate.

[Walt Fricke]

4SD - his sender is not in the cam oil line, so he doesn't have to approach it this way.

Don - The sender most likely screws into an M10x1.00 threaded adapter. I don't know offhand what the diameter and thread of the adapter is (bigger and coarser, of course). M10x1.00 is perilously close to 1/8" NPT tapered pipe thread, but you do not want to use that because it will screw up your threads.

I have a substantial bunch of miscellaneous parts, and when I needed to plumb a mechanical pressure gauge into my system I was able to cobble together something which worked. But had I not squirrled away enough things to do the job, I'd consider purchasing (new or used) the adapter. You can see this in a parts catalog diagram (such as our host has on the website). Then you can figure out how to screw into it something which will connect to your riend's pressure gauge. For that matter, you could install a steel tire valve assembly somehow, and just use a tire gauge you didn't care about. Or buy a 0-100 lb gauge at a good hardware store - they are not expensive and that is what I used. Converting M10/1.00 to 1/8th or 1/4" NPT (what typical gauges require) can be a bit tricky if you are not a machinist.

[KTL]

I was recently fiddling with the oil port on top of the case, so I have some suggestions that you can do to plumb the port for a mechanical pressure gauge.

The port into the case itself is M18 x 1.5 and Walt is correct that the adapter Porsche used is an M10 x 1.0. So you have two choices. Get a M10 x 1/8" NPT

Autometer makes one that is readily available online from places like Summit Racing Auto Meter 2265 - Auto Meter Metric Adapters - Overview - SummitRacing.com

Or get an M18 x 1.5 adaptor and eliminate the pesky M10 x 1.0 dilemma JB Racing and egauges.com are the two I know of off the top of my head

JB Racing - Porsche Engine Components (scroll down to engine fittings and look at part no. 131-035

http://www.egauges.com/vdo_acce.asp?Subgroup=Mech_Temp_Adapters&Manf=All

I went a different route since my mechanical gauge is plumbed with AN-4 fittings and braided hose. I got a M18 x 1.5 to AN-6 (AN-6 is the smallest they offer) adapter fitting from Fragola

Fragola Performance Systems 460618 - Fragola Performance Systems AN to Metric Adapter Fittings - Overview - SummitRacing.com

and then I used a AN-6 to AN-4 reducer to connect to my female AN-4 hose end feeding the mechanical gauge in the dash.

[4sd911]

Originally Posted by Walt Fricke

4SD - his sender is not in the cam oil line, so he doesn't have to approach it this way.

I missed that. This is a good location check the pressure of course this sender does not work with the gauge on the dash, just the light. To compare the pressure readings with the dash gauge I'd think it would be good to check the pressure at the sending unit near the fan, that's the spot I used to verify my dash readings.

[Don G]

Thanks guys,

I think I have cobbled together an adapter (thanks for the correct size Walt) for my friends gauge so I'm good to go as soon as I can talk him in to taking a couple of hours. Probably take another week since he's on holiday (German term for vacation).

I'll report back with a successful conclusion (hopefully).

Thanks all,
Don

[Don G]

Well I'm back and their is no joy in Mudville. Oil pressure still as reported in the first thread.

Oil sender was the correct one and operating properly as confirmed by the outside gauge I used.

Pulled the oil pressure bypass valves out and neither was stuck. Sliding very nicely in fact.
I will say the springs seemed to be awfully strong. Is their a spec for compression testing these ?

Anybody have any other ideas please ?

The only thing I've come up with is I used the cam oil line updated restrictors as suggested in Wayne's book. I believe he indicated a 10-20 psi higher pressure with them. Was thinking of going back to the older ones. What do you think ?

Last question, what are the consequence's of driving it with the very high oil pressure ?

Thanks,
Don

[BURN-BROS]

Did you have the case align-bored?

[Don G]

Aaron,

The case was done at CE they tested it and it was in spec so no line bore was done.

Don