First off a little history about this vehicle: I bought a 2002 Blazer LS 4 Door 4x4 from a used car lot with 163k on the odometer, hoping to get another 50k to 100k out of it. I had owned a 93 blazer that I had wrecked. It had 250k and a braking issue when it ate a silverado's rear end. (Thats another story all together.) Anyway the "new" blazer has been nothing but problems since literally day one. The dealership had it for a total of 3 weeks replacing sensors and eventually the entire computer. Before they disabled the check engine light (how? i don't know.) After that they decided to give it back to me. 2 to 3 weeks later it spun a rod bearing at 3000 rpms (This is when I found out about the Check engine light.) At this point I decided to rebuild the engine with the help of my family (who are diesel mechanics but have rebuilt a few gasoline engines). Mainly Because the dealership had screwed me over.


So after we get it rebuilt she starts blowing blue smoke which as all of you know is somewhat normal for the break in process. However the amount of oil its burning is quite staggering... 1qt every 6 miles.

Here is a list of things we did during the rebuild:
New rings
New pistons
New crankshaft
New cam
New rods and mains
New lifters
New water pump
New head bolts
New intake manifold bolts
New "harmonic dampener"
Heads have been completely re-done by a local machine shop (he also did a little work on the piston connecting arms to give me a slightly higher oil pressure)

And after the rebuild we replaced the following:
Crankshaft position sensor
Fuel pump
Fuel filter
Distributor
Cap and rotor
Spark plug wires (Ac delco)
Spark plugs (Ac delco)
Idle air control Valve

We have taken it to a local shop that did the relearn procedure for the crankshaft position sensor and they also fixed a couple timing issues we had. But it still burns oil (at an alarming rate I might add.) We have used a video scope to look into the cylinders when each piston is at the bottom of its stroke; and the cylinder walls look fine and the pistons are still shiny. The engine has ~130 miles on it already. When the oil is full the oil pressure is ~40 psi on idle ~60-65 during acceleration. It is only throwing 2 codes P300 and one for the check engine light circuit. I have checked the PCV valve, it is not clogged or stuck.

Could high vacuum combined with leaky valve seals burn this much oil?
Is it piston rings?
I have no clue as to what is doing this we are all stumped

I am at my wits end here. I'm almost ready to take this thing down to the scrap yard.

Thanks in advance for all your help

 

Did you stagger the piston rings when you put them in? Meaning rotate the rings so the small gap where the rings come together is 180* apart from the ring below. If you lined them up then you will burn a lot of oil.

Either that or its valve seals.

 

I have to
agree, unless u have a crack that much of a dump is almost certainly non stagerd rings,bad guides/seals wouldnt account for that much oil.is it all burning or is there actual oil driping out the pipe?a drip would indicate a crack

 

When we put the rings on we did stagger them at the angle depicted in a Haynes I picked up for the 2002 year model.

There is not oil dripping from the exhaust, it is all being burnt.

Edit: Upon inspection of the intake valves with the video scope they all appear to be covered in oil.... I think this may be the source of my issues, however this does bring up a question. How much oil CAN it burn with leaky valve seals? If the machine shop put in the wrong or bad seals how bad COULD it be?

 

You better tear the engine back down & see what was not done correct. I have rebuilt many engines & blue smoke is not normal on rebuilt engine break in. Did you hone the CYLINDERS? What was the cylinder taper? What rings did you use (type)?
I just saw your last post after I posted. Where is the oil coming from how can it be burning oil & not coming from the exhaust. I guess I don't understand the problem.

 

We figured a slight amount of blue smoke would be okay due to the fact that we would have to set the rings as well as the valve seals. However... it appears as though I'm spraying for mosquito's at this point

I'm sorry my last post was not clear, the smoke is coming out of the exhaust but its not dripping oil out of the exhaust. When we took the block to the machine shop (which was after we had honed and cleaned the cylinder walls) to have it vatted we had them check to make sure that the cylinders were considered to be in spec (because we were too lazy to check ourselves). When we got the block back from being vatted and the heads back from being completely re-done, he informed us that they (all the cylinders) were "very much in spec for gm standards" as far as piston rings we used "sealed power" that came as part of a master rebuild kit from Oriellys

 

1 gallon of gas to get 15 miles= $3.70

+2 quarts of motor oil to get 15 miles = $5


$8.70 to get 15 miles. I'd tear those heads off and get some from a junk yard.

Your catalytic convertor will soon start smelling like rotten eggs from the sulfur in the oil burning and you'll never get that smell out of the car. Been there done that.

 

My question on the rings was are they chrome or standard steel oil rings? If they're chrome that could be your problem. They take a long time to seat.
The other thing is if you had the block vatted after you honed it & didn't rehone the cylinders you could have a film from the chemicals that are not letting the rings seat. If it wasn't rinsed real good.
Other than missing valve seals or broken rings. The only way to find out is to tear it back down.