I have just replaced my 346,000km EF engine with a freshly rebuilt AU bottom end with EF head, and have started breaking it in. It runs great - smooth and grunty. But the oil pressure has me baffled.

When starting from cold, the pressure is 5-6 bars on the gauge and stays there for about 10 minutes - about 5 minutes after it reaches full operating temp. Then the pressure drops to 1-2 bars in normal driving, not much higher when revs increase, and into the orange zone at idle. It has done this both times I have driven it since the engine went in. The temperature is rock steady at the bottom of the normal range from about 5 minutes driving.

It has a brand new JP oil pump and the engine builder checked the bearing clearances. I am running Royal Purple 10W30 non-synthetic break-in oil for the first week while I run it in. This is what is specified for the AU, but thinner than the 15W40 specified for the EF. I have some Royal Purple full-synthetic 15W40 going in on the weekend.

Should I be concerned about the weird pressure readings? I will be drag racing the car in a couple weeks, getting close to 6000 rpm, so don't want to destroy the engine through low oil pressure. There are no other symptoms, and the pressure does stay high for several minutes after reaching operating temp, so it shouldn't be the oil thinning. The viscosity of synthetic oil doesn't change much as it warms up, so maybe it will be better after the thicker 15W40 synthetic oil goes in - but I'm not hopeful.

Can anyone tell me what's going on here? Thanks.

10W-30 is way to thin, even for a fresh engine. And be careful with Royal Purple - they tell you to run less clearance, but it cant handle high compression applications, and you can get bearing damage.

What clearances did your engine builder use? Were they "measured" or just Plasti-gauged?

Does the oil pressure drop as soon as the revs drop, or does it take a minute or so? And is it a standard or hi-pressure oil pump?

I would get hold of a proper oil pressure gauge and get some good readings before you go changing too much.

And when you drop the current oil, remove the filter and cut it open and check for metal, etc.

Good luck.

Thanks for the quick feedback.

I would have thought that 10W30 would be fine for the bearings since that is what the AU engine runs from the factory. I assumed the thicker 15W40 in the EF was due to the different valvetrain.

I'm pretty certain he miked the clearances, but will check.

It's like the oil pump changes gears: after about 10 minutes, the pressure drops at all rpms. It's a standard pressure JP pump.

I'll see what happens when I put the 15W40 in this weekend and take if from there. And checking the contents of the filter is a great idea.

Thanks for the help.

that probly when the oil has warmed up ...... then thins out?.

Any sign of big end bearing knock at idle when the pressure is low ?
Check the oil pressure sender with a torch for oil leaks - old senders can get brittle, and you can inadvertently damage it refitting it to the AU engine. Usually though if it is damaged. or the membrane has ruptured you'd be reading low oil pressure all the time.

Nope. No knock.

And the oil pressure sender is visually fine. But I did use teflon threadtape to prevent leaks. I wonder if that is enough to cause a weak or intermittent earth to the block.

Hey mate,

I had the exact same problem as you. I had low oil pressure after rebuilding my 97 EL XR6 engine which had 358,000km (shaved tickford Head, .30" rebore, .30" Pistons, decked the block, close and honed the rods, reground the crankshaft, JP oil pump and a 846 reground cam from camtech).

I ended up pulling the engine out and rebuilding it 4 times trying to figure out what was the problem. I told the engine reconditioner and he could not believe it.

Long story short, I bought a $80 6cyl out of a 97 GLI and pulled it down, hone the cylinders myself polished the crank myself, bought new rings and bearings, swapped the oil pump and made sure the block was true and straight. I swapped the GLI head for my tickford one and put it into the car. I started the engine and waited for it to heat up and then I watched the oil pressure gauge go from 60 psi to 5psi.

After buying a different engine, I made the decision to just drive the car, the oil pressure would come up to about 45 psi when cruising so figured I'll leave it and see if I get bearing knock. Well i've been driving it for about 1 year and 4 months (about 7,000 km) and the oil pressure doesn't drop below 15 psi when idling and it gets about 30-40 psi when cruising. There is no knocking from the rods just ticking from the HLA's from shimming the cam clearances.

So now I'm contemplating whether to put my original engine block in, but only when the PTSD goes away .

I don't know why this happened 4 times, I checked and rechecked clearances. The $80 engine actually has oil restrictors in the block to stop too much oil going to the head at high rpm (my original block doesn't have those), but that still didn't help the low oil pressure problem.

BTW: I was using 15W40 Nulon while running in the engine, now I'm using Penrite 15w40 since last service in February.

If you have any questions I'll be happy to answer them.

Cheers.

Thanks heaps! It sounds like your experience is identical to mine. I ran 10W30 break-in oil for the first 300 kms or so, then 15W40 Royal Purple for the next 3000 kms. I switched to 20W50 Royal Purple a couple weeks ago, and the pressure is running a little bit (about 5 psi) higher than it was. It's still low - about one bar, say 15 psi - at idle, when hot. But now it rarely drops low enough for the warning to sound. At cruise, it's 30-40 psi, and a bit higher than that (50+ psi) at WOT. I did about 10 passes at the drags without a hitch.

From your experience, it sounds like I should just stop worrying and enjoy the car. And it sounds like it isn't necessarily a build problem, so the engine builder is off the hook. It's still a bit of a mystery, but the car is a blast to drive, so I'm just going to enjoy it.

On a separate question: Are you running a manual trans? Your Camtech 846 cam looks reasonably wild on paper, with 221/214 duration at .050 and 112 LSA. How choppy is the idle? Any driveability issues? I'm running an RH24B with 195/192/113, but am looking to upgrade to something like the Wade 1673 with 206/198/113. I have an automatic with 2850 RPM stall converter (at current torque levels) and 3.45 LSD, so have to keep it reasonably tame as it's my daily driver. As it is, at the drags it still pulls to 5900 RPM in 1st and 5600 in second, but the top end is weak, thus the need for stouter cam.

Thanks so much for the help.

Hey mate, glad I could help. I was so surprised to see that you had the same problem too LOL!!

To answer your question;
1) I have a stock automatic transmission with the standard torque converter and a 3.45 LSD.

2) I had some rev hang issues and it would hunt when the aircon was off. Because of those problems i had to set the base idle as it would stall if you put the brakes on, but after doing that it was fine to drive in traffic even on hot 40c degree days in summer.

3) Fuel consumption was reasonable when cruising on the motorway (14L/100km avg lowest I had was 12L/100km) but horrible when driving in heavy stop start traffic.

4) With cam at first it felt weak up top I couldn't feel the torque and it would stall a lot, but i played with the ignition timing and it was way retarded so I set it to 0 degrees BTDC and it felt so much better. Also, the auto would change too late for me so and I felt like the cam wasn't being used fully, so last week I finally put a j3 chip into the car and maaaaaaaate it goes like a bat out of hell, it chirps the wheels if you take off fast from the lights and it shifts through the gears like a dream, it also fixed the rev hang and hunting problems i had and gave me a nice lopey idle when the aircon is off.

5) The cam i got was a regrind ($250 from memory) because at the time i was rebuilding my engine there were no billets in Australia to grind up because of that I had to shim up the HLA's to take up the clearances on the cam therefore it makes a ticking noise when it gets hot. My advice is to get billet cam if you can.

I think you would be able to run this cam just fine, you can get similar grinds from crow cams too, but i don't know if they post to NZ.

BTW, are you using an oil pressure sensor? If so is it genuine ford?

Cheers.

Thanks for that.

Yep, the oil pressure sensor is the factory Ford item.