Smoke on Startup, 3.0 CIS six Options

[brilliantrot]

My dad is uprgading from his 912E to a 75 911s with a CIS 3.0 as an autocross car. He is doing this because he is tired of loosing to my 914 and because he cant mod the 912E due to Smog because it is a 76. My question is the motor puffs a rather large cloud of smoke out the exaust on startup concistantly hot or cold but has a totally clean exhaust while running and reving. What would cause this? the motor is supose to have about 30K on it and AASE Motors verifies that the wear on the engine looks to be about this milege while they were replacing the head studs. The only thing that i can come up with is that when the motor is not running some of the 11 plus quarts of oil sitting above the engine runs back filling up the bottom of the engine up to the pistons with some oil leaking past the rings. Is this possible? It makes sence to me because the oil tank gadge goes up (reads more oil) once the engine is started and the massive scavenge pump kicks in. Have any of you 914-6 guys experienced this? Would moving the oil tank to the front solve this? My dad is realy bumbed about this smoke because this engine alone costs more than the entire 912E. Makes one realy appriciate the simplicity and reliability of the T4. I do not know if it makes a difference or not but it is baised on a 3.2 case with the Carrera pump.

[Series9]

It's pretty common and is due to the observations you made about oil settling.

It should stop right after start-up. It it does, I wouldn't worry about it.

[brilliantrot]

Would moving the oil tank to the front of the car stop the smoke? If so, is it ok for the oil tank to be lower than the motor. Will this creat the need to purge the line of air? Will the engine take longer to get oil pressure if the scavenge pump has to move oil all the way to the front and back? Sorry for all of these noob questions but the puff of smoke makes the car some what unacceptable to drive other than as a race car and neithor my dad nor I have any experience with drysump engines.

[IronHillRestorations]

Don't worry about it. Drive the car and enjoy. If it uses a quart of oil in less than 600 miles it's time for a rebuild. Other than that, drive it like you stole it!

Don't move the oil tank for this problem. Nothing is going to stop the smoking on start up. Most all flat 6's smoke on start up, even the new water cooled ones. My 2000 Boxster does it too.

[ConeDodger]

Tell your dad he has a bigger problem than the smoke on start up...


He is still going to lose to your 914 (IMG:style_emoticons/default/slap.gif)

[sww914]

Almost all of them do that. I would say all of them, but I try to be careful not to pass on erroneous information- "some guy online said..."
there might be a few that don't smoke on startup, but I haven't seen them.
Everything's fine, as long as we're not talking about filling your garage with smoke so thick that the neighbors call 911.

[brilliantrot]

ya.The smoke is not that thick but it is enough that you do not want to be standing with in 10-15 feet of the back of the car when it starts up. My dad is starting to go weakend warrior with the project so i am going to try and encouradge that root because the thing sounds redicously mean and loud with a doul inlet Bursh. I did not think that cis cars sounded so lumpy at idle and raspy reving so maby it has 964 cams! Thanks for all of your help.

[rfuerst911sc]

You can also play around with different brands of motor oil. I have found on my 83SC with 3.0 some oils just seem to smoke a little more than others. No oil will eliminate the smoke but may make it less noticable. Also try 15w-40 and 20w-50. I use 15w-40 Shell Rotella dino oil currently but with it geting hotter here in Orlando I may switch to 20w-50. Mine puffs a cloud if it has sat for 3-4 days. Go run it hard!!