Thread: My 350 sbc is smoking

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lt1s10 quote:
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Originally posted by bgrd
lt1s10, if it is a vacuum problem, how do i correct?
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take the pcv valve out of the valve cover and let it run and see if it stops. if it dont clear up in about 5 min. thats not what it is. you can pull the valve cover and see if the drain holes are stoped up also. it shoulnt be the rings they check to good.


it1s10, no change when i took the pcv valve out...

also, pulled the covers again, drain holes were clear...

guess i might have to pull the heads...

Originally posted by bgrd
lt1s10 quote:
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Originally posted by bgrd
lt1s10, if it is a vacuum problem, how do i correct?
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take the pcv valve out of the valve cover and let it run and see if it stops. if it dont clear up in about 5 min. thats not what it is. you can pull the valve cover and see if the drain holes are stoped up also. it shoulnt be the rings they check to good.


it1s10, no change when i took the pcv valve out...

also, pulled the covers again, drain holes were clear...

guess i might have to pull the heads...

I ran a compression test and all cylinders read 130-135psi dry..wet they ran 150-155psi..

i dont see how it could be the rings, the valve guides must be totally worn out. a qt. of oil every 100 miles is a lot of oil.

if the intake was sucking oil from the bottom side then i dought if it would idle good.

lt1s10, that's what so puzzling... it idles fine and runs good...

it just uses way too much oil and smokes

I dont know if the lt1 uses o-ring or umbrella seals but it sounds to me that the valve seals are shot, does it smoke at an idle as well as at high rpm? Typically smoking at an idle would indicate an oil ring problem regardless of compression. If it is valve seals the smoke would be much more pronounced at a higher rpm due to flooding of the head galley.

Originally posted by bgrd
lt1s10, that's what so puzzling... it idles fine and runs good...

it just uses way too much oil and smokes

i dont know you never said how many miles it had and if you cant find anything else i guess it pull down time.

lt1s10 quote:
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Originally posted by bgrd
lt1s10, that's what so puzzling... it idles fine and runs good...

it just uses way too much oil and smokes
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i dont know you never said how many miles it had and if you cant find anything else i guess it pull down time.

It1s10, the motor is in a 63 nova i bought a few months back, the guy who is fairly reputable (sp) said there was about 1,500 miles on the motor, the internals of the engine are clean as a whistle...


Plumb-evil 514 I dont know if the lt1 uses o-ring or umbrella seals but it sounds to me that the valve seals are shot, does it smoke at an idle as well as at high rpm? Typically smoking at an idle would indicate an oil ring problem regardless of compression. If it is valve seals the smoke would be much more pronounced at a higher rpm due to flooding of the head galley.


Plumb, it does smoke lightly at idle, but a lot more at higher revs...

Originally posted by bgrd
lt1s10 quote:
--------------------------------------------------------------------------------
Originally posted by bgrd
lt1s10, that's what so puzzling... it idles fine and runs good...

it just uses way too much oil and smokes
--------------------------------------------------------------------------------



i dont know you never said how many miles it had and if you cant find anything else i guess it pull down time.

It1s10, the motor is in a 63 nova i bought a few months back, the guy who is fairly reputable (sp) said there was about 1,500 miles on the motor, the internals of the engine are clean as a whistle...


Plumb-evil 514 I dont know if the lt1 uses o-ring or umbrella seals but it sounds to me that the valve seals are shot, does it smoke at an idle as well as at high rpm? Typically smoking at an idle would indicate an oil ring problem regardless of compression. If it is valve seals the smoke would be much more pronounced at a higher rpm due to flooding of the head galley.


Plumb, it does smoke lightly at idle, but a lot more at higher revs...

well that's where me and plumb disagree. I never seen a motor with that kind of compression smoke no way. if the compression rings is that good I don't see how the oil is getting pass then. most of the time a motor using that much oil it should be blowing oil everywhere. I still think the vac. is sucking the oil through the intake somehow. all the oil ring do is scrape the oil off of the cylinder wall. most of the time when a motor use a lot of oil its blow by that blows it out of the motor and on the late model the pcv valve picks up the blow by and sends it into the intake and re burn it. the motor sounds like its to solid to be using that much oil, but you got to start some where. if its not a vac. problem then the only choice you got it to put new valves seals or new rings or both. its your call.
how much oil are you putting in the cylinder when you are doing your wet test? if you use to much it can give you a false reading.

how much oil are you putting in the cylinder when you are doing your wet test? if you use to much it can give you a false reading.


lt1s10, i used 4 squirts of the oil can or about a teaspoon a cylinder... sure hate too tear it down because it runs so good...

oh well, guess i will start with the heads and go from there... Gentleman, I appreciate all of your input... Anybody know a good machinst around Waco or Austin Texas?

Another suggestion (easy to find, easy to fix):

A long time ago, a fellow (me) built a 350. Being hot outside, I kept myself lubricated during the assembly. Not being able to think clearly, I used RTV on the intake gaskets. Truck ran great. Started using oil in large quantities soon after. Ran compression check, everything was fine. Pulled PCV, no smoke. Did notice that if I plugged the line going to the carb, there was suction on pcv line.......took manifold off and saw that gasket had slipped on bottom of ports (several) so that engine was sucking oil from the valley. Put new gasket in, threw RTV in dumpster, bought more lubrication. Lived happily ever after. RTV is easy to spot.

mike

robot, very interesting, i will check the intake gaskets once i get the manifold off.. Thanks

JUST KIDDING!!!!

I am no engine building expert by any means with regards to autos, but have rebuilt many many single cylinder motorcycle engines.

Reason I say this is becuase on may occasions compression will be up to spec., if not even higher on an engine that needs a rebuild. This was especially apprarnet on big bore 600cc single cylinder 4 strokes. The rings would be shot, and the top of the piston would look like it was shot with a bb gun 100 times. The top front and rear of the piston at the intake and exhaust post would present as if they were taken to a stone grinding wheel; and the compression would still be up to spec.

IMO you can definately have tired cylinders and rings and still show adequate compression. Just my .02

Originally posted by 30-A Rider
I am no engine building expert by any means with regards to autos, but have rebuilt many many single cylinder motorcycle engines.

Reason I say this is becuase on may occasions compression will be up to spec., if not even higher on an engine that needs a rebuild. This was especially apprarnet on big bore 600cc single cylinder 4 strokes. The rings would be shot, and the top of the piston would look like it was shot with a bb gun 100 times. The top front and rear of the piston at the intake and exhaust post would present as if they were taken to a stone grinding wheel; and the compression would still be up to spec.

IMO you can definately have tired cylinders and rings and still show adequate compression. Just my .02

auto. motors dont work that way.

If you think the intake gasket is the problem, a quick wat to check it is to plug the breather and pcv ports in your valve covers. Remove the dipstick, place a vacuum gauge on the tube, and run it. You sould see pressure, not vacuum.

Could someone post a link to a chart ,which has all the torque specs. for a 350 sbc... TIA