Since this is a Mercedes forum I have a Miata question and I need non-miata brains for advice. And a recommendation for 'engine repair in a can'.

Okay;.... my daughter has a 1991 automatic Girly car+, it blew the headgasket & overheated, so I pull & surface the head & regrind the valves, with new valve seals. Fresh oil change.
It starts up and runs better than before the gasket failure, with compression 170-180# dry. (automatic has lower compression) But Quite peppy!

Now it suddenly smokes really a lot (clouds) blue/white/grey for a few minutes on start up, I thought it might be the vacuum modulator on the automatic, so i unhooked the vacuum line at the manifold, drove around and checked the vacuum line for a/t fluid wetness. Nope..it's fine. Vacuum modulator checks out fine. Remove the oil cap and there is no blow-by, pcv works okay..
Pulled the plugs and all the piston tops are oily wet as though oil is being injected into the combustion chamber. Plugs are fouled black, but work. (i am almost wondering if someone poured oil in the gas)
I think the overheating ruined the oil control rings, or several valve seals came off?;... but dang, it is like there is a hole in a piston the way it smokes.
► Any other ideas (than rings) for oil to get into the combustion chamber?◄

Is there any effective fluid I can pour in the spark plug holes that would free up stuck rings? I need a revelation here.

__________________

"Our Lady of Blessed Acceleration...
don't Fail Us Now"

Done a compression and leakdown test since the smoking?

Yes, these are the compression #s 170-180 with it smoking. I can't do a proper leakdown, but with the compressor hooked up to each cylinder there is indiscernible blow-by into the crankcase, intake or exhaust.

__________________

"Our Lady of Blessed Acceleration...
don't Fail Us Now"

Isn't Marvel Mystery Oil the Duct Tape of the internal combustion/mechanical world?

__________________

1980 300TD-China Blue/Blue MBTex-2nd Owner, 107K (Alt Blau) OBK #15
'06 Chevy Tahoe Z71 (for the wife & 4 kids, current mule) '03 Honda Odyssey (son #1's ride, reluctantly) '99 GMC Suburban (255K+ miles, semi-retired mule) 21' SeaRay Seville (summer escape pod)

Oil smoke on startup that goes away after a little while is usually a problem with the valve seals. Is there a possibility there was a mistake somewhere in the installation of those?

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Anything is possible; but the smoke doesn't really go away. It just spews less when warmed up and driving around.
The Marvel Mystery oil is cheaper than pulling the engine.
What about Kroil? Or Acetone or ATF ??? ......to unstick the rings?

__________________

"Our Lady of Blessed Acceleration...
don't Fail Us Now"

I wouldn't hold out much confidence in a liquid fix, but it's cheap enough to try: Seafoam is specifically sold for just such a try.....

Reasonably well respected in the Miata world, and you can find Miata specific instructions over in the Miata.net garage

__________________
1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife

I have had good luck running seamfoam & MMO in the crankcase of my I4 Ranger, after ~150 miles the engine smoothed out and it began to actually pull up hills instead of lug down.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Not a miata but I have a 190d 2.2 with similiar problems ,how much of MMO do you guys recommend adding ,I believe the motor holds 7 qrts ,alot of oil for just a 4 cylinder.

Years ago I rebuilt a Volvo B20 engine that had been overheated. One cylinder burned oil afterwards. On the cylinder that burned oil, the piston had been scuffed and grabbed the oil ring so it wasn't working anymore.

Half a pint of sea foam in the 190d ,wow ,seems to work.

If it was overheated enough to take the temper out of the oil control rings is a possibility. Any engine that has been run quite a bit with all the coolant spewed out warping the head in the process could have that issue. You might still have decent compression since the oil control rings are different material than the compression rings.

I would not expect stuck rings unless oil baked solid in the lands with the heat. To do so that engine might have to have gotten quite hot. I am not even sure that is even possible.

Yeah; I am suspecting the oil control rings have lost temper, but the compression rings are in better shape.
My daughter didn't notice it was overheating until the motor was making noise. She was commuting 40 miles each way and not watching the gauges like most of us. At 70 MPH, I suspect it overheated quickly.
Curiously, the head was severely cupped, and the valve seats became slightly oblong because of this.

__________________

"Our Lady of Blessed Acceleration...
don't Fail Us Now"

At least the motors are really cheap used, should it be worst case scenario.

__________________
1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

ive had fresh heads blow rings, they wear out together, leaking valves leaky rings, then a fresh valve jobs blows out the old rings. could also be the elevated temp but usually it is just the next worst thing worn out syndrome

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)