Cam tower oil restrictors in a turbo engine Yes/No

[gorskined]

Cam tower oil restrictors are they comely used in the turbo motors ?

My 76 3.0l when i got the non running car the motor had what look like two newly installed cam tower oil restrictors,( the only shiny things on the motor) probably installed just before it snapped its cylinder studs . i didn't put them back in after the rebuild.
My idle oil pressure when at running temp is a little on the low side at idle a hair under 1bar at 950rpms. When first started the pressure is quite elevated as to be expected.

i am using Mobil 1 15w50 full synthetic ( considering changing to 20w50 )

operating oil temp 100c

950 rpm 1 bar
2000 rpms at 2 bar
4100 rpm im at 4 bar

i read a few threads about cam tower restrictors its kind of a Double edged sword.
( but i think most of the information is with the non turbo cars with the smaller oil pumps) . I don't do a lot if idling. but i do occasionally get stuck in traffic.
my farther always told me with the air cooled cars not to idle for extended periods and blip the throttle every now and then when in traffic helps with oiling. not to mention it sounded cool when i was a teenager driving a 911, now that im in my 50s not so much .

so what's the norm for a fair-weather driver turbo built close to stock, restrictors or no restrictors ?

Regards Ned

[flat6pilot]

I added them to my recent 3.0sc to 3.2 turbo build. Oil pressures look great.

[Mocker]

From a caveman standpoint, is it a trade-off between the volume of oil reaching the cams/rockers and the pressure of the oil circulating throughout the rest of the engine? I'm not an engineer...

[motorracer]

I have had them on my car for a little over one hundred thousand miles the last adjustment the cams look fine.

[gorskined]

Originally Posted by Mocker

From a caveman standpoint, is it a trade-off between the volume of oil reaching the cams/rockers and the pressure of the oil circulating throughout the rest of the engine? I'm not an engineer...

Agreed
so this is why im on the fence. One would think the original cam orifices are sized correctly and why did someone say .. "Hey lets restrict oil to the cams so we get more to the rest of the engine"..

[stevie 77 930]

If you search on the engine rebuild section here, you'll find a host of opinions about restrictors from a lot of very smart experienced engine builders. Here are a few....

Cam Pitting, Piston Oil Squirter Testing Without Splitting Case

cam oil line Restrictor/Adapter

Cam tower oil line restriictors

The use of restrictors is a compromise between higher pressures on the bottom end and oil squirters, versus lower volume in the cam housings.

Recently, while helping a friend with a 77 930, we were doing a clutch replacement and engine out service. As it turned out, while doing the valve adjustment, we noticed a lot of cam pitting especially on 2,3 and 5,6 lobes. This car had excellent service history of regular oil changes with correct VR1 oil w/ ZDDP. The motor had restrictors installed from a prior owners rebuild. So this it turned into a much bigger service of cam and rocker removal, disassembly and even oil analysis, etc...

We sent cams and rockers to Elgin Cams in Santa Rosa and they were pretty adamant that the pitting was caused by oil starvation on the 2,3 and 5,6 lobs as a result of the restrictors. Upon reinstallation, we took the route of drilling out restrictors to open them up to 4.5mm as many have suggested. In addition we also removed the cam housing oil tubes for a good cleaning as added precaution.

Upon completion, the oil pressure was just fine along with prefect oil temps.
By opening up the restrictors, you're seemingly right in the middle of adding lower pressure without starving the cams.

Good luck with your decision on this

[stownsen914]

Was going to chime in that one builder here on the forum splits the difference on the restrictor ID and drills them out a bit.

On my race engine, idling isn't much of a thing so I don't worry about idle oil pressure. No restrictors for me. On a street engine I might go with the drilled out restrictor option.

[gsmith660]

There was discussion about restrictors but the concensus was no since I was using a GT3 oil pump and my warm idle pressure is about 20 psi

[gorskined]

Originally Posted by gsmith660

There was discussion about restrictors but the concensus was no since I was using a GT3 oil pump and my warm idle pressure is about 20 psi

i want to put an oil gauge on the car to test oil pressure.. Where is the normal spot to put a temporary gauge to test pressure.

[gsmith660]

Oil pressure is taken off the oil supply to the cam towers

[Speedy Squirrel]

Turbo oil pump or regular oil pump?

[gorskined]

Originally Posted by Speedy Squirrel

Turbo oil pump or regular oil pump?

Good question its a 3.0l 76 row turbo motor with 66k miles . I was the first to split the case. The pump looked perfect so i reused it. The bearings and the crank were perfect also. i replaced the bearings anyways i was concerned about delamination reusing a older bearing ( that burned me once on a 356 build ) .. im assuming the early turbo cars had the larger pumps??? .i never really thought to about it until now . did the early 3.0l come with a larger oil pump?

[tops911]

many years ago (15 or so) I did a lot of research here (and other places) and decided to split the difference, I think I did 4.5mm. My car is an 82 930 with no real maintenance history but it had the cam tower restrictors installed sometime in it's past.

[Speedy Squirrel]

Originally Posted by gorskined

Good question its a 3.0l 76 row turbo motor with 66k miles . I was the first to split the case. The pump looked perfect so i reused it. The bearings and the crank were perfect also. i replaced the bearings anyways i was concerned about delamination reusing a older bearing ( that burned me once on a 356 build ) .. im assuming the early turbo cars had the larger pumps??? .i never really thought to about it until now . did the early 3.0l come with a larger oil pump?

The ‘76 and ‘77 turbo used a pump with a 43mm wide pressure gear. It is not considered the “turbo” pump. The turbo pump has a cast iron housing (appears black compared to the aluminum color of other pumps), and a 53mm wide pressure gear. It also has a corresponding shorter drive shaft.

The cam restrictor is intended to prioritize oil pressure to the main bearings and piston squirters. There is enough pressure to go around with the turbo oil pump, so no restrictors needed. Otherwise, restrictors can be considered, but I would want to have a reason, like observed low oil pressure at idle. Unfortunately, would require taking stuff apart again to make a change.

[gorskined]

Originally Posted by Speedy Squirrel

The ‘76 and ‘77 turbo used a pump with a 43mm wide pressure gear. It is not considered the “turbo” pump. The turbo pump has a cast iron housing (appears black compared to the aluminum color of other pumps), and a 53mm wide pressure gear. It also has a corresponding shorter drive shaft.

The cam restrictor is intended to prioritize oil pressure to the main bearings and piston squirters. There is enough pressure to go around with the turbo oil pump, so no restrictors needed. Otherwise, restrictors can be considered, but I would want to have a reason, like observed low oil pressure at idle. Unfortunately, would require taking stuff apart again to make a change.

Looks like i dropped that ball. i didn't realize there was a difference between the early and late turbo pumps. i just assumed a turbo pump was a turbo pump. i have the stock 4rib style used in the early turbos .. looks like i will be installing drilled out restrictors to combat the low oil pressure at idle .