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just did a rebuild on a 290, runs great, the problem is goin up or down hills it smokes it's @#$ off, pulled the vent from the valve cover thinkin was suckin oil from crankcase. not helpin, oil levels good. made shure to stagger ring gaps, did valve job with new seals. what am i missin? sittin in the shop holdin the pedal it will run perfect with no smoke. just up & down hills.
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I completely understand how frustrating it is after putting in all that hard work on the rebuild only to find your 290 leaving a cloud of smoke behind on every hill. You've clearly taken all the right steps: you said you staggered the ring gaps, did a valve job with new seals, and even checked the oil levels and venting. Given all that you've done, I think the persistent smoking problem is likely due to something other than the internal mechanics of your engine. When you mention that the engine runs perfectly with no smoke when stationary, it points to an external factor that becomes evident under specific conditions.
When you drive on level ground, the engine’s performance might not be enough to heat the muffler to the point of burning off residual oil. However, going up or down hills can create specific operating conditions where the exhaust gets hot enough to start burning any potential caked-up oil, causing the noticeable smoke.
Over time, especially if there was a period when the engine was burning oil before the rebuild, oil accumulates and cakes up inside the muffler. This oil residue can remain even after you've fixed the underlying issues within the engine itself.
One effective solution: muffler BBQ
This involves removing the muffler and carefully heating it in a bonfire to burn off the excess oil inside. By burning off the built up oil, you can clear out the residuals causing the smoke, and... no more smoke clouds on the hills.
Just my humble opinion, keep us in the loop!
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