Originally Posted by Steve@Rennsport (Post 7265824)

Dr. Avery,

JMHO, so take this with the proverbial grain of salt. :)

None of those restrictors goes into ANY engine here since its completely counter-intuitive to reduce oil volume to one of the hottest parts of these engines. Further, this is where the majority of the frictional loads are: cams & rockers and frankly, they need all the lubrication they can get, no matter what oil is used.

Leave them for others, use Brad-Penn oil, change it frequently, and your cams & rockers will last a very long time.

As long as you have 10psi per 1K RPM of oil pressure, you have plenty and I wouldn't be concerned about foaming.

Originally Posted by dkirk (Post 7268219)

I thought the camshaft oil line restrictors were first installed in the 964 engines to prevent oil foaming in the heads. This was a modification by the Porsche Engineering Group that must have proven beneficial from actual engine testing, both from a performance and endurance perspective. Excessive lubricant flow over a cam/lifter interface will not necessarily improve durability; only if the surfaces are marginally lubricated is there a concern. I don't believe this is the case in the 911 engine due to the directed oil spray from the jets in the lube tubes.

I put faith in the Porsche engineering department that they had a good reason to make this restrictor change, based on sound testing.

Then again, I wonder how that infamous intermediate shaft bearing in the Boxter ever made it into production? Probably Sales and Marketing dictating to Engineering again.

Originally Posted by Peter Zimmermann (Post 7660159)

AMAZING! I know that my Tutorial is promised to another site, with an MIA IT guy, but in the mean time I can tell you that I just drove my car. 100F ambient. Cruised a few miles, not exceeding 50 mph, to Stockdale hwy, where I was able to increase speed to between 60 and 70. The oil temp went to 210F and stopped. Similar pre-mod experience was 220-225F in the same conditions.

I then headed for a local neighborhood where I could cruise around for a few miles, which pre-mod would take my car up to 240F+. Today, while able to keep the revs between 3200 and 3800, I was able to keep the oil piston squirter's open (with oil pressure between 3.2 and 3.4 BAR at 3500 rpm) more often and longer. After many stops and starts, the oil temp slowly crawled up to 220F, pre-mod the car might have seen 250F.

This is why my car has spent it's last five summers in the garage. Now, I can't wait to take it for a 40-mile ride at 70+ mph on Highway 99, just to see what happens. Last time I did that I saw temps of 250F, and oil pressure no higher than 2.5 BAR (too low to open the piston squirter's). I will probably wait for the first 105F+ day to do this, so stay tuned.

It would appear, at this point, that Porsche developed these oil pressure "check valves" to allow operating pressure to be high enough to better control operating temperature (because of open piston oil squirter's, used since 1970). If that assumption is fact, then the modification is pure genius. I now consider, after only one hot-day test, that my car, for the first time, is safe to drive in Bakersfield, CA, in the summer. Hot-diggity!

Originally Posted by Cupcar (Post 7268337)

The restrictor was first used on the '91 964 Turbo engine, 964 N/A engines have a different chain housing design without a banjo bolt.
....edit....

Originally Posted by Henry Schmidt (Post 7268942)

The flow restriction/ reduction on the 964/993 engines is built into the design which started in 1989 with the Carrera 4.

Originally Posted by Cupcar (Post 7269296)

Yoda, are you sure here? I am here to stand corrected if wrong.

The '89 C4 3.6 has the late style magnesium chain housing with the oil line cast into it and the plastic connector elbow where the banjo bolt restrictor is on earlier engines, so the piece in question does not even apply to this engine.

On the other hand, my literature shows the 1991 964 3.3 Turbo uses the old style chain housing with oil lines and specifies a banjo bolt fitting that is drilled to a 2.3 mm restriction. To my knowledge, this is where the restrictor began life in MY 1991 .

It is hard to trace back in parts catalogs since the 901.105.361.00 early part has been superseded to the 901.105.361.01 restrictor part, but I don't think it appeared earlier than 1991.

Frankly, I think the restrictors are there to maintain pressure at low RPM to the Turbocharger which also feeds off the main oil gallery. Hot turbo bearings don't like low/no oil flow.

Originally Posted by Henry Schmidt (Post 7269727)

Of course the cam feed restrictor (in question) was not used on the 964/993. My comment was that the reduce flow technology was.
It's hard to see but the restriction in the 964/993 engine is in the transfer tube.
The hole in the previous banjo fitting was 20% larger than the transfer tube used in the 964/993.

http://forums.pelicanparts.com/uploa...1360705018.jpg

Originally Posted by afterburn 549 (Post 7268926)

I knew I was not hallucinating LOL ^^^^^^^^^^^^^^^^^^^^^^