gilmorec61
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- Feb 7, 2013
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Hey guys, this is my first time posting here. Ive got a 1998 Chevrolet Silverado Z71 that I'm having a few issues with. First ill do a little background and technical information.
Engine was rebuilt about 9,000 miles ago. It was bored .030 over, its got a mild Comp cam, LT headers to an X-Pipe then to flowmasters, CAT & EGR Delete, beehive springs, pinned studs, bigger Intake and Exhaust Valves, and everything else in the motor, except for the rockers were brand spankin new when I rebuilt it. Transmission has a shift kit as well as bumped up transmission line pressures. Its got a tune by HPTuners on it, through Vengeance Racing down here in Atlanta. Motor runs like a boss, and pulls all the way up to the redline.
The issue I'm having is that I am burning/losing about a quart of oil, every 750-1000 miles. It seems to burn the most oil at idle. If im at a dead stop in Park or Neutral, and holding the RPM's around 1500, it doesn't smoke. When i let it idle, it smokes. When I cold start the motor, it doesn't smoke most times. If it does, its a very little amount. When I hot start the motor, it normally smokes pretty good. Not Always, but normally. When I floor the motor, and im getting on it, it doesn't smoke. It only seems to smoke at idle, and slightly at the initial acceleration from idle. Now normally, you would think its the rings, or the valve stem seals that could have been messed up or installed wrong when the engine was rebuilt.
BUT HERE IS THE CATCH.
When I built this motor, I originally put it in a 1998 GMC Sierra 2wd. I had the motor in that truck for probably 5-6000 miles. It ran great, and didn't burn nowhere near as much oil as it does now. (It would go through maybe half a quart in 3000 miles, pretty normal). I bought the truck I have now(1998 Chevrolet Silverado Z71), pulled the motors on both, and swapped them. When I swapped them, I didn't touch a single thing internally except the oil filter adapters (as the Chevy was a 4wd and the GM was a 2wd). As soon as I dropped my built motor into the Z71, it started burning oil like I described above.
So what is confusing me is why would the motor run good in the GMC, and not burn any oil, but then the second I put it in the Z71, it starts burning a lot of oil?
YES, when I swapped motors, I had the Z71 retuned for the built motor.
There is no way that a ring, or valve stem seal could just 'go bad' just through a motor swap... The only thing that I could think of is possibly a vacuum problem through the PCV or the Crankcase. I just don't know where to start with diagnosing this.
As I said the motor runs great, and pulls like a ****, it just burns oil.
Help would be greatly appreciated! Here are a few pictures of the Z71 as well.
Engine was rebuilt about 9,000 miles ago. It was bored .030 over, its got a mild Comp cam, LT headers to an X-Pipe then to flowmasters, CAT & EGR Delete, beehive springs, pinned studs, bigger Intake and Exhaust Valves, and everything else in the motor, except for the rockers were brand spankin new when I rebuilt it. Transmission has a shift kit as well as bumped up transmission line pressures. Its got a tune by HPTuners on it, through Vengeance Racing down here in Atlanta. Motor runs like a boss, and pulls all the way up to the redline.
The issue I'm having is that I am burning/losing about a quart of oil, every 750-1000 miles. It seems to burn the most oil at idle. If im at a dead stop in Park or Neutral, and holding the RPM's around 1500, it doesn't smoke. When i let it idle, it smokes. When I cold start the motor, it doesn't smoke most times. If it does, its a very little amount. When I hot start the motor, it normally smokes pretty good. Not Always, but normally. When I floor the motor, and im getting on it, it doesn't smoke. It only seems to smoke at idle, and slightly at the initial acceleration from idle. Now normally, you would think its the rings, or the valve stem seals that could have been messed up or installed wrong when the engine was rebuilt.
BUT HERE IS THE CATCH.
When I built this motor, I originally put it in a 1998 GMC Sierra 2wd. I had the motor in that truck for probably 5-6000 miles. It ran great, and didn't burn nowhere near as much oil as it does now. (It would go through maybe half a quart in 3000 miles, pretty normal). I bought the truck I have now(1998 Chevrolet Silverado Z71), pulled the motors on both, and swapped them. When I swapped them, I didn't touch a single thing internally except the oil filter adapters (as the Chevy was a 4wd and the GM was a 2wd). As soon as I dropped my built motor into the Z71, it started burning oil like I described above.
So what is confusing me is why would the motor run good in the GMC, and not burn any oil, but then the second I put it in the Z71, it starts burning a lot of oil?
YES, when I swapped motors, I had the Z71 retuned for the built motor.
There is no way that a ring, or valve stem seal could just 'go bad' just through a motor swap... The only thing that I could think of is possibly a vacuum problem through the PCV or the Crankcase. I just don't know where to start with diagnosing this.
As I said the motor runs great, and pulls like a ****, it just burns oil.
Help would be greatly appreciated! Here are a few pictures of the Z71 as well.
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