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STATUTORY GRAPE 12-19-2005 07:26 PM

Chevy 350: Black smoke, is it oil or gas
I was looking for a 350 to use for a project and a friend of mine had one but said it was smoking black when he ran it last, he replaced the valve seals but it still smoked so he thought it was a ring problem and pulled it out. Would black smoke be burning oil or gas? Would it be safe to use or how long would it run that way. Is there anything I could run in the oil to keep it from smoking or using oil?

NXS 12-19-2005 07:36 PM

Black is fuel
Blue is oil
white is water

I would fire it on a test stand first and examine the color of the smoke in addition to running a compression check. Look for about 150 in a good 350 chevy, or at least that all cylinders are within 10%. Even at 10% 115 psi is on the low side.

STATUTORY GRAPE 12-20-2005 07:41 AM

I don't have a test stand. Also, when the motor was pulled he put oil in the cylinders with an oil can to keep the rings from seizing, how can I get that out to run it, maybe put a bit of gas in them and light it.

johnsongrass1 12-20-2005 08:42 AM

Unless he really drowned it, he should still fire easily enough,

DAVE.B 12-20-2005 01:01 PM

Worked on V8s for twenty years black smoke is always overfueling, before starting it up spin it over for a while with no plugs in this will blow out the excess oil, warm the plugs up under the grill (honestly), jam the choke flap open 6-7 pumps on throttle if everything is timed up she should fire up

STATUTORY GRAPE 12-20-2005 04:25 PM

"Under the grill" :confused: The motor is sort of cruddy looking, the intake is off and there's a crusty film on the intake valley and the top of the heads, almost looks like carbon but not a hard (like hard crusty oil). I wonder if I should even be wasting my time with this motor. I don't want to start cleaning any of that crap, it's better left alone.

deno 12-20-2005 04:36 PM

Black smoke
Make sure that the choke is open. The top plate on the carb. If not ,throttle up and open it up manualy. If that does not work, get a new carb.

DAVE.B 12-20-2005 04:45 PM

black smoke
Yep under the grill if put back in quick enough they are still hot as in a warm engine this helps the fire up as it stops the plugs getting flooded with fuel.
As for the cruddy film this is oil and carbon due to lack of regular servicing oil acts as a sponge and soaks up carbon ect same as the filter if not changed regular enough will leave a deposit behind Ive seen the valley almost full with this on more than one occasion engine may be a donkey but surely its worth firing up first? if it runs OK drain the oil and refill with 50/50 oil and parafin (kerosene) run until warm drain (thoroughly) and repeat then drain refill and run for 15 mins with some cheapo oil drain refilll and change filter with regular oil will be nice and clean then. Takes a while but it works better than flushing oil and its cheaper. Even then if you freshen it up with brgs, rings, pump lifters if req (dont forget to put cam lube on them and run them in) at least you know its good better the devil you know and all that

STATUTORY GRAPE 12-21-2005 02:35 PM

That's an interesting idea about the kerosene, I've never heard of that. That doesn't affect the lubrication or is that where the parifin comes in :confused:Also, will any of that gunk come off in chunks possibly plugging an oil galley if done like that? . I'm still waiting to hear back from the guy about the motor to see if it was black smoke or blue, seems like it was black. If it was blue I could assume the rings are bad, correct? P.S. in regards to adjusting the choke, it was a fuel injected motor. (89 Chevy truck)

problem solvers 06-17-2006 02:14 AM

Black smoke in an injected engine was probably a clogged air filter. sounds like it was not a very well maintained engine. i would not purchase it because if you get rid of the sludge that is all thats holding this thing together, and may need extensive vatting and pressure wash to clean up to rebuild. Lots of taper results in poorly maintained chevy small blocks and may not be able to be bored out.

78 monte 06-17-2006 02:49 AM

If ya can finger a way to fire it on the ground,perhaps ratchet strap it to something strong.
If it runs good give him $100-150 for it.I wouldn't pay allot with sludge in it.
I also wouldn't run kero in the oil to clean it.I would pull the pan,T cover,intake and valve covers and clean them all out,allong with the lifter valley,tops of the heads and oil pickup with a scrubby and kero or engine degreaser.Throw an oil pump in it,then reasseble it,slob some oil over the crank and cam befor sealing it up to relube the parts.

docvette 06-17-2006 03:30 AM

Doc here, :pimp:

Being as this post is 6 months old..I wonder if he actually purchased the engine..and if he cured the problem :confused:

Maybe He'll post back and enlighten us.. :thumbup:

Doc :pimp:

78 monte 06-17-2006 10:10 AM


Originally Posted by docvette
Doc here, :pimp:

Being as this post is 6 months old..I wonder if he actually purchased the engine..and if he cured the problem :confused:

Maybe He'll post back and enlighten us.. :thumbup:

Doc :pimp:

******** :D

Gr8 '48 bow tie 06-17-2006 06:30 PM

Yes this is an old post but evidently there are some readers still looking at it. I R1. Dave. B has a good flush idea with the 50/50 oil paraffin mix. I have my own way that I have been using for more years than I would like to remember. Without problem I might add. I use 1 gal. diesel and 1 Qt transmission fluid in the crankcase. Start by draining the oil, remove the filter and empty the oil out of it. replace the old filter and fill the crankcase with the solution. Run the engine at idle for about 15 minutes. Wait for the engine to cool, drain the the oil, remove and discard the the filter. Refill crankcase with new oil and filter and enjoy an engine with a smile on its face. Happy engines last longer.



docvette 06-17-2006 07:07 PM

Doc here, :pimp:

If it's not a "Must Get running this weekend thing"....

I have an Internal flush that has served me well through the years..

Pull it all down and send it all to the machine shop for hot tank, Inspection , Valve job, and to pick up a pack of rings and bearings...and if REALLY lifters. While it's out and sitting on the floor..Is the time to do it :thumbup:

Then stop off a the car-wash, and degrease all the shop "Grit" out of the block and parts..and air dry and re~assemble..

Not a BIG fan of additive flushes on super dirty may get some..but most likely you'll just move some elsewhere where it will hide and someday rear it's ugly head and eat an old bearing alive..just my opinion.tho..

Doc :pimp:

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