I was wondering if any of you have installed the oil pressure flow restrictors in the cam oil lines at the fittings where they enter the cam housings. In Wayne Dempsey's engine rebuilding book he urges folks to install that particular 1991 part upgrade that was initially targeted for the turbo but apparently benefits any other 911 it will fit, by restricting oil flow to the cams, not enough to prevent proper lubrication but to prevent excess oil from dropping off the cams to the sump and then foaming up in the sump by crank windage, preventing the oil pump from taking up oil efficiently. He says it increases oil pressure everywhere else in the system except the cams, including to the chain tensioners. My gaskets ooze oil very slightly since I switched to Mobil1 15W-50 synthetic, I wonder if that would make it worse? At any rate, it appears easy enough to do, is there any reason not to?

 

der Mond
I recomend using the restrictors for all the reasons you have stated. The increase in oil pressure to the bottom end of the engine will not cause the engine to leak more oil The seals that you are referring to are controlling oil being splashed around the various parts throughout the motor. The increase in oil pressure is lubricating bearings and the like. This addtional pressure is not applied to the seals, they will be subjected to the same amount of "splash" as before.
Hope this helps.
tcpott

 

Thanks, and for such a cheap and easy update I'll be sure to do it!

 

Made this modification about three years ago. There's no downside and there are advantages as detailed. Takes ten minutes.

 

Interesting discussion here: https://rennlist.com/forums/showthre...il+restrictors

 

I would like to add that, IMHO, I do not understand the big deal. By design, the oil pump will produce a certain volume of oil at a given speed. If you add the cam restirctors, the total amount of oil pumped does not increase. Instead, more of it is directed to the lower parts of your car while reducing the flow to the cams. I have no idea if this is a good idea or not.

Some food for thought. If your oil pressure gauge was on the downstream side of the restrictors (instead of the upstream side), you would see a drop in oil pressure. Most likely you would find this distressing. Why is it ok on the upstream side?

One more point to ponder. When Porsche when to the cam tower restrictors, I think they may have also increased the total pumping volume of the oil pump. If this is the case, I would not be surprisied to find out that the larger pump with oil restrictors pumps about the same volume of oil to the cams as the older pump without restrictors. Does any one have any data?

Bottom line... Porsche Engineers are not dummies. A crown jewel of their company is their engines. They built their reputation on small but powerful engines that last. I would tread carefully in trying to change what they did without fully understanding the consequences.

 

Harry,
Thanks for the link. I guess especially upon that feedback from Steve W, I'll just leave my restrictors alone. But I do have to say that Porsche through the years, despite the great engines and cars, has done a number of things that have made some their engines notoriously unreliable and expensive to fix. Fortunately they have also been willing to correct a lot of these issues. But again, thanks, I'm just going to let it be, it's a highway car and it runs just fine!
Dennis

 

Dennis: Please remember that those notoriously unreliable moments usually happened as a result of being under enormous pressure to keep their company afloat in the face of air pollution control requirements growing ever more stringent. I'm not making excuses for them (well, maybe a little!), but just imagine their sadness at not being able to bring the '68 911S to our shores, then get backed into a corner when they put thermal reactors on the '75 - 77 cars, followed by the decision to stop Turbo production for the states from '80 - 85. Mag cases didn't usually pull head studs until displacement reached 2.7L, and the first Dilavar head studs didn't start to break until many years after the early SCs were out of warranty. Yes, Porsche made a big mistake with the first year and a half of C2/4 production, but you have to give them credit - they fixed the heads on the early leakers under warranty. They're a small (tiny) company by GM/Ford standards, but they really are always on the cutting edge of safety, electronics and performance. Some of their mistakes have, I think, been caused by their innovative engineers constantly thinking and doing, even dreaming, outside of the box. Without those engineers Porsche would have never been able to build the 917, the 959, or the '07 Turbo featured in the new AutoWeek, the one that went 0-60 in 3.38 seconds. Yes, they've screwed up from time-to-time, but I think that, even then, they had the best of intentions.
Pete

 

Pete,

Thanks for you thoughts and I agree that Porsche for such a small company has done so well at teh "bleeding edge".

I would be interested in hearing your take on this oil restrictor thing. I, for one, would like someone "in the know" tell me I am all wet on my take on the situation.

Happy Holidays.

 

Harry, et al:

Quite obviously, there are many and somewhat conflicting opinions about whether the cam oiling restrictors are appropriate for the older (3.2 and older) engines. Everyone ought to do what they are comfortable with and I'd simply offer some things to consider.

1) I'm not sure that Porsche A. G. grasps the major differences in today's oil formulations as sold in North America and the rest of the World. Camshaft and rocker wear is on the increase and reducing oil flow (for cooling as well as lubrication) to these parts is counter-intuitive to me. I know what I see.

2) As you wisely pointed out, Porsche made the changes when the oil pump's specification was changed that boosted oil pressure and scavenging. I've seen other examples where an apparent "update" was inappropriate for older motors that were not so equipped. I think Porsche matches oil pump capacity to several things; squirter size, engine displacement & operating RPM, system specification (coolers, filters, pressure relief valves to name a few) and one must be mindful of this.

Bottom line? One should do whatever makes them happy and if one needs to see 20 psi at idle for assurance, so be it.

For my part, I'll not use the restrictors for the engines we build which are mostly competition powerplants that require all the cooling & lubrication they can get. We have other ways for providing sufficient oil pressure and improving scavenging without resorting to those things.

 

Steve, Thanks for "weighing" in. I see your feelings on the subject have not changed so I take it things are continuing to degrade due to the reduction of ZDPP in our oils.

First ethanol and now this.... sigh

 

I sure do appreciate the detailed treatment of the topic by folks with know-how and experience, and I guess I'll do a search for ZDPP now, unless you'd like to eloborate, Harry. Looks like I have nothing to lose by leaving my cam oil lines as-is. Pete, thanks for a particular historical insight into Porsche I was missing. Ownership has brought intense mood swings due to the incredible passion that allowed me to go into debt to buy the car, learn to tweak it, then fear losing my baby to a head stud. I'm sure I'm not alone, and that's why questions like this are so important to us guys that will do anything we can afford and do ourselves to make our cars that much better, but are terrified of screwing them up. What with the valve guide and head stud fears and these reports of cam wear my guts tell me to bathe and baste those cam housings and heads. And my affection for the company has been bolstered, so thanks again. For now, despite 140K miles, when I turn the key, it sounds and runs strong to red line. Tentatively planning a trip to the Grand Canyon and back this spring. Just need to complete the lowering rite of passage this April.

 

Long winded topic. I'll just get you started by pointing you here: https://rennlist.com/forums/showthre...hlight=Oil+EOS

Basically what appears to be going on is that the lube oil sold in the USA has reduced zinc and phosphrous over earlier formulations due to a drive by EPA to protect the catalysts. These elements help prevent wear on roating parts so us guys that keep our car beyond the lease period are at risk for premature engine failure.

 

I had no idea of the cat-additive issue so thanks for the heads-up! I guess I'm lucky I use Mobil1 15W-50.