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Blue Smoke

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if you are getting blue smoke all the time it's probably your rings, does it get a lot of idle time? if it does you might be able to reseat the rings by covering part or all of the radiator and put it on a hard pull for a while. remember to watch your temp gauge though. you should be ok up to about 260 degrees F you would need to keep it above 230 degrees for about an hour. if you have a LOT of miles on the engine though you'd be better off with new rings and sleeves. if you only get blue smoke from start up to operating temp. it probably is your valve seals and guides.

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I have a 1974 RD 685 w/237. I'm burning about 1 gal of oil in 8-10 hrs. Lots of blue smoke out the stack, however no excesive blowby out the crankcase breather. I'm wondering if the valve guides and seals are junk, not pistons and rings

Could be that the seals are out of the impeller shaft in the turbocharger. That would cause exhaust smoke, and high oil consumption.

Every engine I've seen with bad rings or valve guides had extreme blow by out the crankcase breather tube, and if it's really bad it would pressurize the crankcase to the point of blowing oil out the breather.

You state there is no excessive blowby, therefore I'm thinking turbo seals

Pull the intake & exhaust pipes off the turbo & look for oil in there, also grab the turbo impeller & try to move it sideways. If it has sideways motion, the turbo bearings are bad.

If you find oil in the intake end of the turbo, the turbo is junk.

If you find oil in the exhaust end of the turbo, remove the turbo from the exhaust manifold. If the exhaust manifold is dry, but the exhaust end of the turbo is oily, then the turbo is junk.

If the exhaust manifold is full of oil, then you've got bad exhaust valve guides.

Check these things first- no sense doing a complete engine overhaul if the problem is in the turbo or valve guides.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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