Oil line restrictor - yes or no. Please help.

[HJT911]

Having read a lot of existing post’s in different forums, and following the interresting discussions regarding this issue it seems that there are two parties (pro and contra restrictors) were the latter fears that the increase of oil pressure and reduction of foaming is bought dearly since top end is suffering from reduced flow to the cams.

Although a lot of post’s are referring to a supposedly existing Porsche TSB, nobody has ever provided a copy of this doc.

Anyone out there who can?

[jason2guy]

ive had these sitting in my parts box for 3yrs. ive read all the posts i can.
my car has 250M on it. my logic is, if it has ran great for all those miles without the restrictors why put them in?

[mtb001]

I have set also sitting in box, look at them every time I work on something in engine bay, my vote is no.

[db_cooper]

I think if you have good oil pressure at idle when the engine is hot (about 1bar)..don't bother with the restrictors.

Some 911s would flash the oil pressure warning lamp when hot at idle. The owners manual for the 3.2 models even refers to not being alarmed when it happens..it is normal.

If you have one of those engines..use the restrictors.

[JAR0023]

Do you have sufficient oil pressure when the engine/oil is hot? If so I'd leave it alone, but this is just my opinion and I'm not an expert.

I don't have them. My car has 150k miles on it I still have great oil pressure at idle when hot and my oil pressure pegs at 4 bar on the gauge by 2500 rpm. I don't figure I need more oil pressure.

I read all the threads here and elsewhere trying to determine if this was something that would benefit my car. I came to the conclusion that there is no consensus. I was not interested in increased oil pressure but the reduced oil foaming and increase scavaging. When driving at higher rpms for any amount of time I was seeing oil back over into my intake. Running my oil level low didn't help. I ultimately decided not to add the restrictors and see if I can address the oil foaming with a different brand of oil. -J

[JJ 911SC]

I did install them a few years back. It did increase the pressure but according to the PP info that was an additional benefit.

Here is the spiel from PP:

In 1991, Porsche redesigned the camshaft oil line restrictors with reduced diameter orifices on the 911 Turbo. The intended benefit was to reduce oil foaming within the camshaft housings while maintaining enough flow to effectively cool the valvetrain. However, additional benefits were apparent since the smaller orifices provided consistently higher oil pressure across the engine's full range of operation. Minimize the frothy cappuccino effect and increase your oil pressure simply by switching to these updated oil restrictors - installation is a piece of cake! Includes two (2) restrictors, and six (6) sealing rings.

[GaryR]

My take is if were to install them I would drill them out to a size half way between stock and their original small size. Will give slightly better bottom end lubrication while not reducing top end by much.. but i'm not putting them in my new build. Porsche engines have great lubrication if treated properly (oil changes and good oil). Look at this motor, never been opened and I have to believe not treated like a baby, at least aesthetically..

This is how it looked fresh out of the car-


Crank, gears, bearings look brand new!

[kugelfischer]

I've also got a set sitting in my tool chest. With all of the mixed advice on these, I've decided not to install for now at least. I was worried for a bit that my old mag cased engine had low pressure until I checked it with a mechanical gauge. Turned out that everything was in top shape, only my 40 year old sender was out of spec.

[sc_rufctr]

Wayne recommends them in his rebuild book. I hope he chimes in.

[HJT911]

Thanks so far to all for their comments.
ut what I am still looking for is that so often mentioned dubious Technical Service Bulletin
From my point of view no information could clear the point in question better than a statement from POG via those TBS.

[Chuck.H]

I'll look when I get home for a mention in the parts and tech reference book, which contains many TSB's, but it seems we need to look in an early 90's version of it.. not sure when mine was printed.

I've had them in my engine since the 30k mile mark (when I got my car) - Porsche made the update and I trust they usually make incremental updates for good reasons; something like this I would not question.

Chuck.H
'89 TurboLookTarga, 370k miles