Engine smoking at start-up

[LCOX]

I have a 1974 911 with a 81 3.0 CIS engine upgrade. When I first start the engine after sitting for a few hours or overnight I'm getting white smoke for a couple seconds out the tail pipe.

-the engine does not smoke continiously, only for a second or 2 when it's first fired up then it stops. The car runs strong with no missing.

-here is what I know
1. the oil level is ok (not overfilled)
2. all spark plugs are clean. not oil fouled or fuel fouled
3. all 6 cylinders have good cold and hot compression test readings in the 160-180 range
4. had the emissions tested with the co reading at 2.2 and hydrocarbons around 2600
5. the cat converter has been taken off with a cat bypass pipe installed with a new o2 sensor.

-This cis injection has the lamba brain and wiring harness on it as well.

Any ideas. Thanx. L

[kidrock]

How often do you drive it, and how far? It sounds like you have some condensation in your oil tank, and you may not be getting the car warm enough to burn it off. This is common. Telltale sign: yellowish "cream" is visible on bottom of oil filler cap.

[twistoffat]

A puff of white smoke on start up is nothing unusual on our cars.As long as it clears after a few second its okay

[db_cooper]

Very normal on the 911 engines. The oil tank drains down and floods the sump after a length of time, like overnight. Some oil will work past the rings and exhaust valve guides. Poof, you have some smoke.

They did it when new..no worries.

[LCOX]

Thanx guys. L

[DRACO A5OG]

By testing your car without the cat, it will for the 1st start up bellow out a ploom of white/grey smoke. When you put the cat back on it will be able to dilute it a bit better.

For my car, only in the morning then the rest of the day it is fine.

Try to also allow you car at the end of the drive day to let it sit for 30-60 seconds at idle. For whatever reason the next morning it is less smoke, sometimes none at all.

J

[LCOX]

ok I'll try this. L