Anyone used the oil restrictors ??

dick911 · 01-04-2006, 03:24 AM

Hello to all,

In Wayne's book "How to rebuild..." he mentioned the oil restrictors in the camshaft housing as an update (found in 90's Turbo's). The oil line from the hydraulic tensioners is connected to these.

Did anyone install these restrictors and what did you notice?
Higher oil pressure is claimed when engine is idling.

I don't ask this because of hesitation regarding Wayne's knowledge but I'm wondering if this update is worth my time and money .

Hope to hear from you!

gr.

Dick

911 SC Cabrio

cgarr · cgarr's Garage

I put them in my 86 last summer, my hot idle was just under 1 now its just under 2 Its easy and cheap to do, the new size hole is 2.5mm The pressure jumps up quick with just a little rpm increase

dick911 · 01-04-2006, 04:47 AM

Hi Cgarr,

Thanks! Sounds hopefull...

Others for any reaction?

gr.

dick

sammyg2 · 01-04-2006, 07:55 AM

I have them on my SC, they increased the oil pressure about half a bar at full temperature, maybe a little more.

Eagledriver · 01-05-2006, 07:59 PM

I had them and removed them. I felt the pressure was too high. I'd use them on an engine that had low oil pressure or one with an early (pre 76) oil pump. These engines don't seem to have a problem getting enough oil pressure. High oil pressure will wear the aluminum intermediate shaft gear quicker IMO.

When I say oil pressure too high I mean over 100 PSI at anything above 4000 RPM. If your engine stays below 100 PSI with the restrictors on then I wouldn't worry about it.

-Andy

dick911 · 01-05-2006, 10:57 PM

Thanks Eagledriver,

Hmm, sounds not good to me...

Any comment from Wayne possible regarding the things Eagledriver noticed for the older engines ?

Can this higher oil pressure wear the aluminum intermediate shaft gear quicker ?

Hope to hear from you.

gr.

Dick

aigel · aigel's Garage

Why are we talking psi? Anyone have psi on their gauge? There is a valve that bleeds off excessive oil pressure. Mainly it should act when the engine is cold. 45 bar or so. This valve will prevent that any mechanical parts wear quicker than normal.

I installed the restrictors in my 81sc. It improved my oil pressure across the board. Especially on 110 F track days, that was very welcome. I'd rather have all the oil I can at the crank.

Talking about track days: The main reason people put these restrictors is NOT increased oil pressure, rather than to decrease the risk of oil foaming - messing up the oil scavenging process. At very high rpm operation, there can be too much oil going to the valvetrain, resulting in foaming oil in the crank case.

Porsche makes these restrictors. They are put in all later engines (3.6 IIRC). It's not like Wayne came up with them and now tries to pawn them off by advertising them in his book.

George

dick911 · 01-06-2006, 12:53 AM

OK Aigel,

Thanks for your reply.

MY SC is a '83 - 204 HP (living in Europe...) with a rebuild top end and new rod bearings.
Main reason for starting this topic is my worry regarding the valvetrain and cams as there will be lesser oil around that area due to the restrictors...

Will there be more wear in the valvetrain?

I heard of '90 > Turbo's in Europe (which first got these restrictors by Porsche indeed..) which had worn out outlet valve stem guides at about 50.000 miles (80.000 km) !!
(Due to the oil restrictors ? was the first thing that came up to me...)

Anyone an answer..??

gr.

dick

aigel · aigel's Garage

Dick:

Prematurely worn valve guides plagued many porsche engines long before these restrictors were used. Only the SC 3.0 seemed to have had few problems. I am not sure about the early 90s turbos but I think the early 3.6 may have had some valve guide wear issues too. I think these issues were related to bad valve guide materials or sometimes valve seals that were "too good", keeping all the oil off. I hope others with more knowledge can chime in.

If you'd starve the valve train of oil, wouldn't you think the cam lobes and rockers would suffer first? I am no expert, but compared to the cams and rockers, the valves / guides should not need much oil to be sufficiently lubed.

If these restrictors would kill the engines, you would have heard about it by now on this board and elsewhere. I also thought that it was a Porsche recommended upgrade?

For me the decision was easy, since I run the car at desert temperatures on the track. That's 40C and up, in the non existing shade!

Greetings to Holland,

George

dick911 · 01-06-2006, 01:30 AM

Hi George,

Good input.
Indeed, if there were any troubles regarding this update we sure would have read it here on this forum.

So far no other reactions about it to found anywhere on the internet...

Well, just ordered them, € 3,- each... well worth to try it...

Thanks,

Dick

PS: still no reaction from Wayne ?

Henry Schmidt · Henry Schmidt's Garage

We use them as a matter of fact on all engines we build.
Back in the mid eighties before Porsche put them on the 91 Turbo we were making them and installing them on every engine. They will not increase oil pressure anywhere but idle (unless there is a clearance problem in the cam tower) and it is a noticeable improvement on most engines. We designed them to use on the 2.7 because they were plagued with low oil pressure at idle when hot.
The oil flow to the valve train was reduced on all 911 engines after the introduction of the 3.6 in 1989.

aigel · aigel's Garage

Great input Henry!

George

Eagledriver · 01-06-2006, 05:36 PM

My guage on my 72 reads in PSI. I only gave you my opinion. I'm not attacking anyone who has a different opinion. I just think that if there isn't a problem with the old then I don't want to "fix" it. As far as foaming goes-that problem hasn't been around since oil improved 15 years ago.

I don't think the oil restrictors do any harm other than causing oil pressure to be higher than I like. They seem to allow plenty of oil for the valve train. One of my friends I race with likes the oil pressure to be as high as possible and he is a very competent engine builder, I just disagree with him.

-Andy

cgarr · cgarr's Garage

Doesn't the oil bypass when it gets too high?

Eagledriver · 01-07-2006, 12:22 PM

It does. You can see it when your engine is cold. The pressure on my engine when it's cold will climb to about 130 PSI and then jump down to about 90 when the pressure relief valve opens. I don't know the spec for the relief and safety valves but I think they are around 8 bar (120 PSI).

-Andy

afterburn 549 · 01-07-2006, 07:35 PM

put them in mine,Best mod I ever did!! ( for the $$)

dick911 · 01-08-2006, 11:38 PM

Hello to all,

Thanks for your input !!

gr.

Dick

Henry Schmidt · Henry Schmidt's Garage

It is not uncommon for oil pressure to be excessive during start up with or with cam tower oil flow restriction. The reason for the higher (some times too high) is cold oil viscosity.
The cold oil over powers the oil pressure relief valve.
We see oil coolers exploded regularly at the tract on cold winter morning. Oil viscosity not restructures are the problem.
The addition of an update check valve relief kit will also raise the oil pressure. If you rebuild an engine and install an update kit you will naturally see an increase in oil pressure.

s5uewf · s5uewf's Garage

If the engine is rebuilt and restrictors are installed, is it still recommended to use 20w oil or is it safe to drop it to 10w synthetic? Would this reduce pressure, reduce parasitic drag, and still provide protection for bearing and shearing surfaces?