All 911 based, air cooled Porsche engines since 89 have this type of oil flow. 946, 965, 993, TT all have reduced flow with no indication of head temp or oiling (additional wear) problems.
It is true that all of these engines ran improved cooling with duel coolers.
The duel coolers were added in conjunction with the removal of the engine mounted cooler. I'm guessing that the Porsche engineers calculated BTUs generated by the 3.6 engines (both NA & Turbo) and using hydrodynamic and thermal conductivity calculations, determined oil flow and cooler efficiency before proceeding down this path.
They (Porsche) had 9 years of production and 17 years of highway testing with no apparent indication of any problems.
Supertec has used this restricter technique since the mid 80s and we have never seen an issue in our early engines in both race and street applications.
We actually made restricters before we could buy them.
Now it's easy, just call Pelican Parts and order yours.

There was long long thread on this quite awhile ago by people that understood the thermodynamics of things... ( oil )..in the end all agreed with Porsche that cooling would be better ! I know, less sound worse,,but how do you argue with success ??
Just do it your i.c. will be happy

I upgraded on my 2.2 rebuild last year. Included the restrictors, carrera pump and relief valve mods. My oil pressure was a little too high with cold pressures around 7-8 bar. After reading some other threads here, I drilled them out a about one mm and now I see pressures about 6.5-7 cold and 4 bar at normal temps.

If you're making 4 bar at idle when the engine is hot then you have a problem.
That sounds like the wrong oil pressure sender for your gauge.
The cam fee restricters should only effect idle oil pressure and not pressure at higher RPMs.

+Thamks Henry - let me clarify. Those pressures were at 2000-3000 rpm. At idle it drops back to normal of about 1-2. I think everything is fine now.

Should I install these restrictors without any other modifications on a stock 2.2s with carrera tensioners?
Others hve mentioned bypass mods, different oil pumps, etc., will these work as a stand alone?

Yes , they will add idle oil pressure with no other modifications.

Henry,

When you were making restrictors before Porsche came out with them, what size was the orifice in the restrictors you were making?

Was the orifice size larger, smaller, or the same size as the C2 restrictor orifice size?

Thanks for the info!

1/8 INCH. slightly larger than the C2 restricter.

So now that the C2 restrictors are available do you use the C2 restrictors on all your engines or do you install 1/8" restrictors?

More specifically - what size restrictor would you use on a 3.0 SC or 3.2 Carrera engine with stock oil pumps?

Thank you greatly for the quick reply!

We use the 91 Turbo restrictors in all our engines.

Have these restrictors been proven effective after all these years? Any down side?

On the C2 /3.6 liter engines Porsche took the same approach as we did. They went with a slightly larger hole.
Our conclusion was that the factory 965 restricter was slightly too small so we bore them a to match the ones we make.

I bought the cam line restrictor from PP for my rebuild (72 2.4 to 2.5 (84 to 86mm p/c) T-to-E, oil bypass mod and a 4 rib pump (courtesy of Henry)). While I'm sure it'll be fine as-is from the discussion here, should I consider boring it out to 1/8"?

Benefits appears to be better oil pressure at idle only and less work for the scavenger pump. Anything else?

Anyone see higher engine temps or cam wear? Anyone experience too high oil pressure when cold?

Recently rebuilt my 2.4. Did the bypass mod but not the restrictors to the carerra tensioners. It does not have any oil pressure issues but more at idle when hot is somewhat desirable.

This mod scares me a bit as our engines are really oil cooled and the non roller lifters need alot of oil (zinc issue) (I cant define alot).

Collective brain trust here say to do it?

Thanks,

Chris
73 911 E

YES

The original 965 control oil control fittings were 2.5 mm or 3/32"
When I wrote that we made our fittings 1/8th, I was mistaken.
We actually bore them to 4.5mm. My conversion was in error.

Just being courious... how did you discover that the stock 2.5 mm was to narrow. If I got it right you started this mod before the factory, just with a larger port hole. Are there any experiences that made you keep the larger than the 964T testrictors?
Best regards
Pelle

Just to be clear here, 4.5MM is just a little larger than 11/64, or a #16 drill to be more accurate.
Bob B

There were no bad experiences. We used a smaller (than stock pre-91) hole to create oil pressure a lower RPM especially with turbo squirters and 4.5 mm seems to accomplish that goal.
Then the factory came out with the 965 control fitting and we used it because it was cheap and accomplished the same goal. Shortly after the 965 control fitting we noticed that Porsche elected to use a control fitting more closely aligned with our original fitting.
Guessing that they may have seen issues (we had not) we went back to our original 4.5mm bore.

Just red a couple of threads about the restrictor with all the pro and against. I am still not sure if I should fit or not, but what I do not understand is that some of the guys decided to choose something in the middle of the earlier 6mm and the new with 2.5mm, so about 4mm. But this make no sense at all, as when you look closer to the cam housing, you see below the adapter that there ist the squirt tube where the oil entries. The hole there is about 4mm (verified by drill), so an adapter of 4mm does... NOTHING. So it has at least be smaller than this, otherwise it has no effect. If you like to have something in the middle you have to fit a restrictor of about 3.3mm (half the cross section)

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