'78 3.0 SC - Smokes when hot

[Hellraiser]

Hello,

my buddy has a problem with his '78 SC and we like your input.

A few months ago, his engine started to smoke (oil consumption) when hot.
Until it is hot, it doesn't smoke and then the smoke is suddenly there.

We tought at first it was the heads, so we had them machined and had
new valve guides and caps installed.

This didn't solve our problem.

We also noticed the engine runs fairly hot and oil pressure when hot is 1.5 bar.

We didn't split the engine case but checked the cylinder barrels and piston rings
to replace a few broken studs and everything was ok.




So eventually, the engine is back in the car, we replaced a lot of things, but this
didn't seem to solve our problem.

Did anyone already experience this? maybe a pressure relief valve stuck?
Oil level is ok, we didn't overfill.

Thanks!

[Norm Faustino]

Oil control rings? Just throwing it out there. I know they gum up and stick. Maybe run a de-carbonizer Like techron through the fuel system.

[kodioneill]

Are you sure you didn't overfill? What is your process for checking the oil level?

[theiceman]

i cant belive you did all that work and didnt put hydraulic tensioners in ... just sayin ....

[911SauCy]

Originally Posted by theiceman

i cant belive you did all that work and didnt put hydraulic tensioners in ... just sayin ....

There aren't tensioners

Doesn't the oil line over the cam cover on right side denote hydraulic tensioner feed of sorts?

[Norm Faustino]

Here's what it looks like with hydraulic tensioners.

[ossiblue]

Originally Posted by 911SauCy

There aren't tensioners

Doesn't the oil line over the cam cover on right side denote hydraulic tensioner feed of sorts?

No. Hydraulic tensioners are pressurized by oil that if fed from those lines. There would be a T connector in the line with a small, metal hard line that enters a fitting in the cam tower cover. That engine in the pic does not have hydraulic tensioners.

[Hellraiser]

What's wrong with mechanical tensioners?

Oil checked with engine hot and running at idle.

We're working on 911's for about 10 years now, so usually we know
instantly what the problem is, but now we don't know what to do.

We can pull the engine again, but that's pretty useless if we don't
know where to look...

Heads were professionally rebuilt by a well known company, so there's
no doubt this was done like it should.

What worries us is the high oil temp and relatively high pressure when at idle.
And off course the smoke...

[timmy2]

You said you removed the cylinders and everything was in spec.
I have to ask, did you set the 3 ring gaps in the correct orientation?
What type of cylinders, Nikasil or Alusil?
Did you replace or re-use the rings?
How many miles on the bottom end?
Have you done a hot engine compression test and leak down?

[Hellraiser]

Hi Timmy,

ring gaps are ok, type of cylinders I'll have to ask.
I do know they were installed by the PO a few years ago.
My buddy re-used the rings and broke an oil control ring when
re-installing the barrels, which he replaced by a new one.

However, all plugs are equally fouled.

Bottom end has 180.000km's, about 112.000 miles.

Leakdown numbers I'll have to ask too.

Thanks!

[Hellraiser]

Despite everything, the car runs very smooth, fast, doesn't hesitate and hangs on the throttle...

[Hellraiser]

Oil pressure rises about 1 bar per 1000rpm, so that's normal too.

[Joe Bob]

JB's rule

#1

If it smokes, run it at nite....

#5

Ignore the oil ads....

#31

Run it lower than mid mark on on the dip stick.

#42

Use 20/50 DINO VR1 Racing Valvoline.

#67

Ignore the stupid oil gauge.

There are others....just ask.

[Hellraiser]

We already put 20W60 in it, but it doesn't make a difference to 10W40

Mid of the dip stick is where we are at.

Oil lines all warm up like they should, thermostats are ok too...

[Joe Bob]

Compression check?

Leak Down?

[Hellraiser]

My buddy did them, but I'll have to ask him the numbers.

I'll keep you updated on them.

[tuchan]

How much smoke and consumption are we talking here?

How hot does it need to get before it starts burning the fat?

Ignition timing OK ?

Pinging?

Just thinking here out loud, retard and see how it goes...

[Hellraiser]

Hi Tuchan,

car starts smoking at about a centimeter under the red line.
the highest we see the temp go is up to half a cm under the red.

it doesn't smoke when cold and you don't see smoke when you
drive behind it. It looks to be only smoking at idle, but that could be
my imagination.

consumption unknown, we did about 300km since the rebuilt.

ignition timing, valve timing and valves adjusted according to the small book.

car isn't pinging, we have ron98 octane fuel out here

[fasterlaster]

Being a 911 newbie I'll throw this out there, as something I have observed with aircooled VWs. What about crankcase pressure? Potentially pushing some oil past the rings during normal operation causing the smoke? I'm wondering if the smoking changes at all if you take the oil cap off while running (yes, I knwo a huge vacuum leak)

[tuchan]

Oil cooling is needed I think from where I sit and what you are saying.

What is the ambient temp' where you are?

It is probably just getting too darn hot and simply going though it. If it does not smoke till it gets that hot then there is probably nothing wrong with it, apart from oil over heating..... currently.

Smoke under full throttle or when backing off from high revs, idle ?

I get good high octane fuel over here in Oz also but still need to watch how far I advance no matter what fuel I am running. CIS on this car can only cover so much.