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Nailhead Blue Smoke


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Over the years I come across folks who have blue smoke coming out the exhaust mainly on start up. Even on a rebuilt motor.

One way to reduce oil flow though valve guides is by chamfering the end of the guides with a special tool. Has anybody done this with success?

I found this solution in a 1970 Engine Service Manual.


If only valve stem seals should be used (intake only) what type?

Who has them?

Tom Kunek


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One thing you don't want to do is limit the oil to the guides they are set up from the factory the way there are for a reason. The guide clearance on the intakes is .001"-.003".

Exhaust is .0015"-.0035". IF you try to set them up on the tight side of the specs. the valve stems will seize in the giudes. Don't forget also that the stock OEM valves are stainless which also require more clearance.

IF you look closely at the top of the guides they are rounded from the factory makes no sense to make the modification in my mind on a stock build.

 You could use just about any type of modern seal where you have to machine the top of guide to install. .500" to .531" is a standard O.D. size that comes in many diff. types of material. Just about any good machine shop will have them in stock as they are for a SBC mostly as well as MANY others.

What's the big deal about a little blue smoke on start up anyway this way the top ring is sometimes getting a little lubrication & the top ring "should" last longer.

    Just my thoughts on the subject.


Tom T.

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My dad was a professional mechanic for a number of years. He always tools me tgat if your engine didn't use a little oil, then the engine wasn't getting fully lubricated.  As Tom says a puff of oil smoke means the top rings are being lubricated.  

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