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Engine smoke 350 help

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BRife

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Boulder,CO
Hey guys I am new to this so just trying it out.
I am trying to figure out what is causing my 350 to smoke so bad. Its in a 1972 K/5, but its not the original engine.

If I let the truck sit for awhile about 2 weeks or so and I start it I will get blue smoke right on start up. It will go away as its idling but once the engine starts to warm up 200 degrees or so it starts to smoke again and its constant. At idle when its warm you can only see the smoke if you were looking for it , its hardly noticeable. But rev the engine to 2000 or so rpm and it becomes a constant puff of blue smoke that does not stop, and as you run it more the idle smoke also becomes heavier.

I did do a compression test, I had 75-80 psi on each cylinder expect number 2 from the front on the right side was at about 60psi and the 3rd one on the right side I got a reading of 0psi. And the right side is the side that is smoking, the left is fine I have duels with headers. I just dont know what would cause me to get 0 psi on that piston, I added oil to that piston and nothing changed.

I am hoping its not rings, I just bought this truck 3 months ago and I dont feel like doing a whole engine replacement or rebuild. The truck runs stronger then ever, does not miss at all and has so much power under the pedal.

Any help would be great,
thank you.
 
Pull your valve cover and check the valves. Easy simple and fast. Maybe it's in the top end. What your describing could be a valve stem. Oil in the cylinder to check compression only helps the rings. No change leads to what's above the oil. Rpm effects it leads me to think you might have a bit of a rattle? Are you checking compression by rotating the crank or adding air through your tester?
 
I also have oil sitting at the end of my tail pipe after I run it for awhile
 
I am not hearing any weird noises or rattles I did a compression test with a tester screwed into the spark plug hole and then cranking the engine for about 8 seconds.
 
Smoking after it sits for a while is usually a sign of valve seals or something in the head.

Also 75-80 psi seems low if I recall.

What do the plugs say.
 
Yes I know I thought that was low as well but thats what they all say so I just going by that unless my tester was bad. there is oil on the threads of the plugs but not really on the inside, the inside on my bad piston was a little wet but hardly
 
At 0 PSI I wouldnt expect it to be the rings, unless they are severely worn, sounds more like a valve hung open. Smoke at start up is worn valve stem seals, and 80ish PSI is low. Sorta sounds like maybe the engine is just tired.
 
454Sub said:
At 0 PSI I wouldnt expect it to be the rings, unless they are severely worn, sounds more like a valve hung open. Smoke at start up is worn valve stem seals, and 80ish PSI is low. Sorta sounds like maybe the engine is just tired.
Click to expand...

I missed 0 psi in one hole. Either you have some major valve issues or your testing methods are flawed
 
I'm going to say you have broken rings which accounts for your smoke and also the very low compression numbers. A typical chevy V/8 usually has anywhere from 125-200 psi of compression with the carbed engines being closer to the 125-150 range and the FI engines being between 175-200 psi.
 
BRife said:
Hey guys I am new to this so just trying it out.
I am trying to figure out what is causing my 350 to smoke so bad. Its in a 1972 K/5, but its not the original engine.

If I let the truck sit for awhile about 2 weeks or so and I start it I will get blue smoke right on start up. It will go away as its idling but once the engine starts to warm up 200 degrees or so it starts to smoke again and its constant. At idle when its warm you can only see the smoke if you were looking for it , its hardly noticeable. But rev the engine to 2000 or so rpm and it becomes a constant puff of blue smoke that does not stop, and as you run it more the idle smoke also becomes heavier.

I did do a compression test, I had 75-80 psi on each cylinder expect number 2 from the front on the right side was at about 60psi and the 3rd one on the right side I got a reading of 0psi. And the right side is the side that is smoking, the left is fine I have duels with headers. I just dont know what would cause me to get 0 psi on that piston, I added oil to that piston and nothing changed.

I am hoping its not rings, I just bought this truck 3 months ago and I dont feel like doing a whole engine replacement or rebuild. The truck runs stronger then ever, does not miss at all and has so much power under the pedal.

Any help would be great,
thank you.
Click to expand...



Did you open the throttle wide open?
 
0 psi on a cylinder is usually a bent or burnt valve. Or a hole in the piston but not likely. If you pressure tested it correctly and you were getting around 75 psi, the rings are wore out or the valves are not seating. you need to get another engine or rebuild yours as already said.
 
Broken rings on just that one piston you think? Correct me if I am wrong but if I had broken rings wouldnt I notice a loss of power, or misfiring?
I believe this engine is from the late 70's to mid 80's and I know many of their engines during that time were toned down due to emission and fuel issues?
Just my thoughts, I am just trying to figure out all my options before I decide to pull the engine.
Thanks guys
 
Yes I had the throttle wide open.

I have been looking for 350's anyone know where I could get a good running 350 for cheap?
 
The problem is its a risk buying one you cant hear run, but junkyards always have a supply of SBC, and probably BBC if you want one of them instead, all pretty cheap. Just check it over real good for any glittery oil or nasty sludge, usually a sign of a damaged bearing, or in the sludge, a neglected motor. Its not always a solid standby, but its something to look for.
 
I have one. Needs a carb and intake. 100 and its yours. It's in Oregon though
 
Did you pull the valve covers yet? Maybe just get away with a top end for now if cash is tight. If you find a messed up valve, pull the head and than inspect the pistons. You can get remans around 2k if you check around. You have to have a good core though.
 
Yes I am in colorado, dang I would take that deal now if it wasn't the transportation issue.
Thank you anyway, I am just going with that I have a burnt valve and instead of trying to rebuild, I'm looking for a new one to drop in.
 
What do you mean get remains around 2k?
And yes I pulled the valve covers and replaced the seals. Everything looked normal and i cranked the engine, the valves were moving and seemed to be in sync with oneanother but its hard to tell from just the top end. What would you recommend doing if I were to just work on the top end. I thought about replacing the valve seals, but with the 0 compression I thought that was a waste of time and not the answer to the problem.
 
Pull the heads and have them checked/rebuilt and while they're off inspect the piston tops for any signs of detonation or obvious holes in them then re-install the heads after they've been done and HOPE that you don't have any broken rings or broken ring lands on the pistons. You could also just pull the heads, then drop the pan and pull the pistons out to properly inspect them before you dump any money into it and then depending on what you find move along accordingly.
 
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