Post rebuild high oil pressure

[cmovic]

I just completed a full rebuild of a 100,000 mile 911SC engine. I bought this engine with a broken head stud to replace the 175,000 mile engine in my track car.

My question is about the oil pressure. I installed the updated pressure springs and pistons as well as the more restrictive cam tower oil line adapters that Wayne recommends in his book. A new oil pressure sender was also installed during the rebuild.

When I did the initial start and run-in I noticed I had 5 bar of pressure at 2000 rpm. Since then it seems a little lower but still is pegged at 5 bar anytime I'm over 3000 rpm. Every 911 I've driven has pretty much followed the Bruce Anderson quote of "1 bar per 1000 rpm is normal."

Is my elevated pressure normal for an engine with the turbo cam tower adapters? If not where should I start looking for the problem?

Thanks in advance for your advice.

[cmovic]

I'm replying to my own post... Hope that's ok

Back when I brewed beer, the saying was "relax, don't worry, have a homebrew." The stakes are a little higher than $35 worth of malt and hops so I find it harder to relax. It's starting to look like I should drive more and worry less.

I went for a drive tonight and took some notes about my oil pressure. My idle is really high right now so that skews things a bit too. Here is what I found:

RPM BAR
1000 1.5
1200 2.0
1600 3.0
1800 3.5 (lowest idle)
3000 4.5 - 4.75
3600 5.0
4400 5.1+ (pegged)

Non-synthetic 20/50 oil at 160-180 degrees,

There's a little more detail. I'm still interested in opinions but frankly I'm less worried about high pressure oil after driving the car than I was this afternoon.

Aside from this issue, the engine feels great. It pulls hard in 5th. I'm really looking forward to getting out on a race track in 2 weeks.

[Eagledriver]

I removed the cam oil restrictors after I noticed the high oil pressures. I think I would do that if I were you or use thinner oil. It's very easy to put the old cam fittings on (if you still have them).

-Andy

[cmovic]

Andy -- thanks for the tip. I do plan to run Mobil-1 20/50 once I'm past break-in. I'm guessing synthetic oil might drop the pressure a bit. I do have the old fittings. I'll clean them up and give this a try. Replacing them is definately easier than dropping the oil to check the bypass plugs.

[cmovic]

I swapped out the turbo cam fittings for the stock ones. Or at least tried to. While torqueing the left side fitting it broke off in the case. My heart nearly stopped... Luckily an easy-out extracted the other half. I guess there's a good reason to change out 27 year old parts.

Taking a look at the old and new fittings, they are nearly identical except where the turbo fitting narrows down near the bottom. Since it was 11:30 pm and I need to drive the car asap, I drilled out the turbo fittings, cleaned them up and reinstalled everything.

Here are the new numbers:

RPM BAR
1200 1.75
1400 1.8
1800 2.75
2000 3.0
3000 3.8
3300 4.0
4000 4.25
5200 4.8 -- seemed to be the max pressure

Same 20/50 non-synthetic oil at 160 degrees.

I didn't hit the same data points as before but this is close enough to see the trend. These numbers look like the values I am used to seeing on the previous engine.

If I see a pressure drop after switching to synthetic I'll think about reinstalling the restrictor fittings. Otherwise I'm going to leave the oiling system alone.

-Vic

[Wayne 962]

Both before and after look okay to me...

-Wayne