cold start smoke screen

[gorskined]

car is still running great but my intermittent cold start smoke swow has become less intermittent and more of a constant . after sitting for 8 to 10 hours when started a big puff of smoke for 3-5 seconds then a slight burn off for another 20 seconds. then no smoke at high or low rpms
i have been reading lots of old posts to try and narrow things down and would love some input. all stuff i never knew would be an issue or even existed. This is my first turbo motor before this i messed with regular 911s and 356s . The car is not an original 930 its a 80 sc with an early 76 3.0 row turbo motor .

i believe my car has the correct 930 oil tank and my scavenge pump is connected to the correct tank drain port. but I'm not 100 percent sure, the tank has two identical fittings right next to each other . i am considering removing the scavenge pump oil drain line from the tank while the car is warm and off to see if I'm connected to the one that has the tube above the oil level .
My tank running warm/ hot oil level is 2/3 up between low and max on the dip stick. so if i remove the line and nothing comes out im good or if a quart drains out i may need to lower my oil level to 1/3 on the stick or so . if my tank fully drains out than obviously I'm on the wrong tank connection.

My second concern is i read some thing about a ball check valve ball bearing on the oil line and a Rothsport valve.
i don't recall ever seeing a ball check or check valve on my turbo oil supply line but im not sure if i need it . its an early turbo motor where the oil line is fed from the block that feeds my 4,5,6, cam rail and the chain tensioner. The oil line goes up and runs across the front of the fan. not sure where later turbos cars are feed from possibly lower this is why they need a check valve ??? also i don't understand how oil would get to the turbo if there was a ball check . some mention springs and others don't. im assuming its a ball check or used to seal off residual pressure when the car is off not a check valve any input on weather i need a check valve /ball check or not and exactly where to install it would be very helpful. I am kind of at a loss with this because all the posts are between people who know where this ball is and what its used for i would rather install a check fist to see if it fixes my cold smoke issue . than attempt the oil line removal from the tank . the more i think about it i would think i do need the ball check as gravity would cause the oil to syphon and pull into the scavenge tank .


. i thought it worth mentioning when i was cleaning all the hardware for this motor i did notice one small banjo fitting similar to the ones on the fuel distributor with a ball inside it . i have no idea if it went to this motor or if it came from my spare parts stash when i was looking for nicer fittings than ones that were on the motor so i didn't use it .

Thanks in advance

Regards Ned

[gorskined]

Red arrow is where my turbo oil line is feed from it uses the typical large banjo bolt .

[gorskined]

looks like the issue is not the turbo
i pulled the turbo drip tank plug when the car was cold, it only had about 5 or 6 oz of oil in it . i also lowered the tank level to the minimum spot on the dipstick .. no change still get the puff of smoke during cold start up. going to try the Rothsport check valve.

[Alan L]

That check valve sits in the triangle of death (oil leaks) to prevent too much oil draining in to the turbo. Which makes lots of smoke on start up. That may simply be your problem.
Alan

[Bucketlist]

Turbocraft also sells a check ball kit for the oil feed.

https://parts.turbokraft.com/collections/911/products/turbocharger-oil-feed-check-valve

[gorskined]

Originally Posted by Alan L

That check valve sits in the triangle of death (oil leaks) to prevent too much oil draining in to the turbo. Which makes lots of smoke on start up. That may simply be your problem.
Alan

my oil line is not feed from the rear triangle. the early cars are feed from the right side cam oiler. unfortunately the take off orientation of the hose will not allow for a gravity ball check . i also removed the drain plug on my turbo oil pickup tank over night only had a few ounces of oil came out . and the car still blew smoke that morning, so I'm fairly certain its not not building any residual pressure there and blowing by the seals also the smoke is instantaneous .. i ordered a Rothsport ball check, fingers crossed hopefully that will do the trick . I'm at about 200 miles going to do the first oil change and add the Rotsport valve .. i received it yesterday its very nicely made should be for the price .

[gorskined]

The Rothsport valve solved the cold start smoke issue .. The ball check is nicely made . I'm assuming the ball check spring is just a little stronger than the standing oil tank pressure as i could easily blow air past the ball check before i installed it . once installed and run the tank always maintained the warm oil level even when cold and not running . simple fix for an embarrassing issue.