Engine smokes, what's next.....

[GIBSON]

Ok, I built my 73S engine nearly 2 years ago, down to the main bearings. I used the same 100K mile pistons/cylinders with new rings. The top ring land was on the edge of acceptability. I knew I was taking a chance with the rings ever seating properly (used Deves rings btw). The engine runs great but I took it out this morning for the first time in 2-3 weeks and it smoked so bad nobody could stay behind me for the first mile or so. Really heavy white smoke then it pretty much stopped.
So, what's next.
1. tear it down to the P/C's and replace them with something else
(new 2.2S for higher compression)?
2. tear it down completely and build to RS specs (expensive but nice gains in hp and torque
3. Send out the P/C's to a machine shop to see if they can be salvaged (bigger top ring land, new rings-- or is it too difficult to
get these S P/C's to ever seat properly??
I know I'm going to have to do something. Any chance I've done damage to the engine main bearings, should I have the case
machined for tighter tolerances like so many of the magnesium cases need?
I'd appreciate any suggestions.
Thanks

[1fastredsc]

Before you jump to suggestions, make sure that your oil level wasn't too high in the first place. I know i made that mistake after putting my motor back together and started freaking out thinking that i did something wrong. Next, if you believe it's the rings, check the breather hose from the engine and see if there's oil in it. Whenever blow by occurs from bad piston rings, usually the extra pressure in the case forces oil out the breather. hope that helps

[konish]

White smoke, sitting for 2-3 weeks and generally colder temps around the country....I'd say forget about it. Probably a product of a stone cold engine, moisture in the exhaust and the normal moisture as a by-product of combustion...

R/
Dustin

[Oldporsche]

White smoke?

That may be steam. Condensation in the cylinder?

Blue smoke generally is oil.

Take your time and don't jump to conclusions. Diagnose this carefully.

Good luck,
David Duffield

[Grady Clay]

Bruce,

Don’t do anything without much more investigation.

I will speculate that you dutifully keep the oil level topped up. After sitting for 3 weeks, the oil level in the tank and sump equalized. With (properly) plenty of oil, the level can get up to the exhaust valve and even cylinder level. This allows oil to seep past the rings or marginal exhaust valve seal and into a combustion chamber. When the engine fires, that oil is dumped into the muffler and it takes a while to burn out. The result is like a “mosquito eradication project” for a while.

I recommend you drive the 911 daily for a while with some “spirited” extended trips. Over a period of several (many) weeks, do repeated cranking compression and cylinder leak tests immediately after long drives (and one before you drive.)
Keep track of your oil usage, that involves careful oil level measurements under the same conditions.
Regularly measure the exhaust gas for unburned HC.
Try another 3-week storage under the same conditions and see if you can duplicate the problem.
Above all; don’t disassemble the engine for this one episode unless there are other indications.

Best,
Grady

[GIBSON]

Thanks guys, good suggestions. I tend to keep my engine at the
bottom end of the dipstick level so I don't think there was too much oil. I'll check the breather for oil as well.
Maybe I am rushing into too much concern here, the last leakdown I did was all at 92-93%.
I did install the reducer oil fittings on the cam oil feed lines
at the cam tower. This has given me higher oil pressures but
I wonder if it can contribute to other problems as well.
Think I'll go drive the P#@! out of it for a while and see what happens. I'll keep you informed.
Thanks again for the input.

[nostatic]

Originally posted by Grady Clay

I recommend you drive the 911 daily for a while with some “spirited” extended trips.

The single best advice ever given on this BBS.

[klatinn]

Hi,

Just don't let yourself be caught in CA with a smoking engine. Smoking in CA is considered almost a criminal act

Regards,
Klaus

[Wayne 962]

Read this first:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm

-Wayne

[GIBSON]

Good comments from all, the smoke is white for sure, not blue
or darker color and stops when the engine reaches a certain temperature. It does not smoke at all when warm.
I'll give it a good run for several days straight and see what happens. I'd rather not tear it down again after 2500 miles.
Wayne, good article and very helpful.

[Steve87-911]

My wrench once told me, "I don't even want to *hear* about cold engine smoke".

Like others have said, drive the thing. And not just short hops for a six pack. Nice long (hour minimum) drives. She'll like it.