350 burning oil but runs like new.

[T-ROD]

I have a 350 I recently got from a yard from a C1500 Chevy truck for my blazer (Tahoe), it runs good and with new vacuum lines, sensors, and exhausts parts etc. It gets quite a bit over 15 MPG ( 15 MPG ballpark avg.) It runs smooth and runs strong, it has power, just smoke after running about 5 minutes (after warm) or if under load pulling like if I put it in drive I can hold the brake and hold it at somewhere around 1400-1550 RPM'S and it will fill my driveway with smoke, but at a idle while driving its OK unless it sits for more than 1-2minutes then it will smoke, or if I hit the gas pretty good from idle it will blow a puff of smoke out behind me a few foot and pretty thick then it stops, kinda strange but it runs great and I didn't have a lot of moolah on me to buy a crate 350 with a rump de bump can, I was just lookin out for a regular 350, Like I said I didn't have a whole lot of money on me so I got some new parts like plugs exhaust manifold bolts and another set of manifolds and pulled another water pump and alternator I had off the other motor for about 7.5-8k miles, the motor only really smokes much if its close to or over 195° or operating temp (195-212) it doesnent overheat, and it does it idleing or revved, I revved it to around 2900 rpms to see how it did and its about the same, only smokes under moderate load or mod rpm loads 1500 to 2500, and heavy acceleration from off idle, other than that it runs like brand new, it doesnt blow out smoke from dipstick or oil fill, and it doesn't overheat or anything crazy, that's why I'm looking at suggestions, 5W-30 Pennzoil, W\ACDelco Oil filter, and 3\4 quart of Lucas works very well with a regular 350 about 5000 miles, its good but what's good with this? Maybe wix filter ( for higher flow) and maybe penzzoil 20W50 or some kind of oil treatment, Im looking for some suggestions as of what it could be as I'm knowledgable about motors but nobody knows everything and its always nice to gave a friend suggestions, BTW, I have been on this site for very well over 2 years but I havent been on it for a while, so as to new additions, Welcome and thanks

 

[glockholiday]

Your title says burning oil but you don't mention a level change on the dipstick. So hows the oil level after say, 3000 miles. Dark smoke out the tail pipe can be fuel. Especially at the loads you mention.

 

[yevgenievich]

The discription does sounds like engine is loading up with too rich of a fuel mixture.

 

[Georgeb]

What color is the smoke? If it's bluish white it is most likely oil. I would suggest running 10w30 rather than 5w30. Had an old 307 chevy that smoked like that. Ran like a scalded ape but smoked like mad. My 78 350 also smoked. Not as bad but still..... A set of valve seals may help but otherwise it could be worn guides or oil control rings. I used to run 10w40 in the summer and 10w30 in the winter. STP oil treatment helped too.

 

[DoubleDingo]

What color is the smoke? If it's bluish white it is most likely oil. I would suggest running 10w30 rather than 5w30. Had an old 307 chevy that smoked like that. Ran like a scalded ape but smoked like mad. My 78 350 also smoked. Not as bad but still..... A set of valve seals may help but otherwise it could be worn guides or oil control rings. I used to run 10w40 in the summer and 10w30 in the winter. STP oil treatment helped too.

What he said. But could also be loading up some. Thicker oil is better for sure. As is the oil treatment, not just for thickening up a tad, but also for the zinc modern oils lack. Our flat tappet engines like a little zinc.