White smoke after rebuild - HELP

[mmasse]

I just finish the rebuil and started the engine ( '97 993 ) following the procedure on Wayne's book

The plan was to let it idle at 2000RPM for 20 min, but there is a LOT of white smoke coming of the exhaust, so I turned it off after 5 min

After posting on the Engine Rebuilding Forum, a fellow member mentioned that it might be the old oil on the exhaust system burning. So, I started the engine again and let it run for 20 min, and I had the impression the amount of white smoke had gone down significantly. So, I changed the oil and got ready to go for the first drive, as per Waynes book instructions. But, the engine started throwing a lot of white smoke again. I run it a couple of blocks and back home. Let it idle at 2000RPM for 5 more minutes and the white smoke would not stop.

I took the exhaust and headers out and it looks that Cyl 6 is the one throwing oil. So, I decided to perform a leak down test.
I tested the three cylinders on bank 2 (cyl 4-6). I got pretty consistent leak numbers. 18% on cyl 1; 15% on Cyl 5 and 19% on Cyl 6. On all of them you can hear a bit of air going to the crankcase. No noise on the intake of exhaust sides.*
I was surprised to see such high numbers on an engine with new rings, but I thought it might be that the rings are not seated yet.*
What confussed me is that Cyl 6 which is the one which seems to be throwing oil (wet exhaust oulet and manifold) did not show any difference with the other cylinders.

Can anyone suggest how to go from here, before the obvious "take everything apart again!!" ?

thanks in advance
*

[timmy2]

Did you take it for the drive Wayne suggests? The long downhill run with accelerator off will help seat the rings more than anything. A couple of blocks?
Mine was smoking lots when I did my rings last fall, I did exactly what Wayne say's to do in the book and no smoke at all after the first couple of good drives and nothing now 3000 miles later.

[brads911sc]

+1

Originally Posted by timmy2

did you take it for the drive wayne suggests? The long downhill run with accelerator off will help seat the rings more than anything. A couple of blocks?
Mine was smoking lots when i did my rings last fall, i did exactly what wayne say's to do in the book and no smoke at all after the first couple of good drives and nothing now 3000 miles later.

[Nostril Cheese]

You need to seat the rings. Thats your problem. Go out and rev the piss out of it.

[mmasse]

Well that encouraging!

No, I only did a couple of blocks because I was scared about the amount of white smoke coming out of the exhaust.
And it felt like the engine was not pushing.
Like if it was running on five cylinders. I will start it again tomorrow and post a video

[Nostril Cheese]

Just remember to get equal pressure on both sides of the rings. That means acceleration AND engine braking.

[timmy2]

Just starting it and then not driving it until it gets fully warmed up and then worked, will do more damage than taking it out for a 1/2 hour hard drive with lots of on and off acceleration.
If you don't have hills do a lot of high rev downshifts, almost the opposite of jackrabbit starts.
These cars are not like todays cars, they need to be broken in.
Drive it like a race car. That is how it was designed.

[Porchcar guy]

Listen to the group..So many people write that after doing this or sitting for a long time...their car smokes...take the D**m car out and drive it for at least 30 minutes. I had a paint job done and it took months...picked it up and on the way to the interior shop, I thought I was driving a fog machine...went away quickly but was a sight to see and I am sure that all the other cars on the road were laughing at the guy in a Porsche...smoky boy !!

[Tippy]

Rings won't wear in for that short of duration. The cylinder walls in the 911 are a lot smoother crosshatch wise vs a common V8 which when honed IIRC are 4 times rougher accelerating ring seating.

I don't like taking new motors to redline until at least 500 miles (debatable topic!) but the higher RPM decels supposedly helps seating rings. Maybe try some big hills if you can and just rack up miles period.

Only alternative is to teardown motor but not enough miles are done yet.

[mmasse]

Here is link to video where you can see what I am talking about

You will notice that for thevfirst 30 seconds there is no smoke but then it starts coming quite a lot

Porsche 911 Start up after rebuild - YouTube
*
Let me know what you think

For now, I am waiting until tonight to go out so to hide my shame on the dark night :-)

Best

[timmy2]

Looks like mine did when I first fired mine up and ran it at 2k rpm. Really stunk up the garage and the air around the house.
Took it out for a few uphill and downhill runs up to 5k rpm,(about an hour's worth) changed the oil and it's been great ever since.
You need to seat those rings under load deccelerating and accelerating.....

[brads911sc]

What Dennis said.

[DohertyCM]

My mechanic once told me not to run synthetic at first just so the rings would seat. He always told me that the synthetic was just too slick.

But how long does the smoke come out.....could it be an over service issue? If the rings were not put in correctly it could cause this as well...

[timmy2]

OP claims rings were installed correctly in the motor rebuilding thread. I'm hoping he's out driving the car as suggested, and will report back to us all in the morning that he has successfully smogged his neighbourhood for mosquitoes and the car is running a lot clearer now.

[mmasse]

Ok, I am back from a hard drive and I don't have very good news.

I pushed it quite hard with lots of acceleration up to 5000RPM and downshifts.

Initialy the car felt like runing in 5 cylinders but when I stepped on it it pushed really good. Above 3500RPM and until 5000RPM it feel very good on the lower range RPM still feel like not reacting well.

Smoke continues to come out, but it seems that a bit less.

I returned home to check thinks around and I found an issue. When I took the oil cup out to check the oil level, oil bursted out of the filler hole with pressure!,,it seems that the crankcase is getting some pressure, I wouls assume from the not seatec ring???

Here a couple of clarifications which might be important. The engine is running a Supercharger. I took the precaution of disconnecting The oil breater that is supposed to be connected to the air intake. the reason for this is that I suspected the Supercharger is creating too much vaccum on the intake and sucking oil from the breather. This was a problem I had before rebuilding the engine.

Based on tjis would you reccomend a new run tomorrow after it cool down overnight. Or shoul I surrender and open it up again!!

[mmasse]

Ok, I am back from a hard drive and I don't have very good news.

I pushed it quite hard with lots of acceleration up to 5000RPM and downshifts. Aprox 8-10 miles.

Initialy the car felt like runing in 5 cylinders but when I stepped on it it pushed really good. Above 3500RPM and until 5000RPM it feel very good, but on the lower range RPM still feel like not reacting well.

Smoke continues to come out, but it seems that a bit less.

I returned home to check thinks around and I found an issue. When I took the oil cup out to check the oil level, oil bursted out of the filler hole with pressure!,,it seems that the crankcase is getting some pressure, I would assume because of the not rings no sealing properly???

Here a couple of clarifications which might be important. The engine is running a Supercharger. I took the precaution of disconnecting The oil breater that is supposed to be connected to the air intake. the reason for this is that I suspected the Supercharger is creating too much vaccum on the intake and sucking oil from the breather. This was a problem I had before rebuilding the engine. The breather to the crankcase is still connected.

Based on this would you recomend a new run tomorrow after it cool down overnight. Or shoul I surrender and open it up again!!

[mmasse]

Some reading on other posts might have answered the question about the pressure buil up on the case. When I disconnected the breather to the intake, I also blocked the second outlet on the filler neck, which means that the oil fumes are trapped and build pressure inside the tank. I will connect a catch can to that second ( smaller ) breather on the filler neck, tomorrow....and maybe try one more run, to see if it gets better...or worst!!!

[Tippy]

It sounds like you got it.

[DohertyCM]

Have you checked your plugs? what do they look like?

Have your checked your crankcase breather tube on the back of the motor? is it blocked?

Have you checked your throttle body to see if oil is getting to the cylinders via the intake?

Are you sure your supercharger is not leaking oil into the throttle body?

Just questions to help us help you....

[mmasse]

Originally Posted by DohertyCM

Have you checked your plugs? what do they look like?

I checked the plugs: 1-5 look dry, maybe a bit of black dust on them. The plug on cylinder 6 is clean, but wet. It actually smells as gas, not oil.!!!

Originally Posted by DohertyCM

Have your checked your crankcase breather tube on the back of the motor? is it blocked?

Checked. It is not blocked

Originally Posted by DohertyCM

Have you checked your throttle body to see if oil is getting to the cylinders via the intake?

Are you sure your supercharger is not leaking oil into the throttle body?

Just questions to help us help you....

There is no connection between the intake /Supercharger and the oil tank, since I disconnected the breather that goes to the intake. I connected the second breather connection on the filler neck to a catch can.