My 75 has developed a problem at startup. It smokes alittle only when starting. Not even enought to add oil monthly. Anyway I beleive its the valve seals or at least thats what Ill try first but I have a question on which one to use. I see a listing for umbrella type or oring . Whats the difference and does someone have any recomendations. Thank
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Re: smokey startup
The "O" ring seals fit into the bottom of the valve retainer and essentially block oil from running diretly down the stem onto the top of the guides. Depending on the design, and "umbrella" seal not only blocks the flow from on top of the spring retainer, but also provides some limited protection from splash. If the car doesn't have too many miles on it, the "O" ring seals, which are the only factory installation in your engine, may ahve hardened ansd lost tension against the retainer. I would replace them in any case. If you decide to add some insurance in the form of umbrella seals, be careful to make sure there is adequate clearance for the thickness of the seals between the bottom of the spring retainer and the top of the valve guide. It get's quite tight in there at full valve lift and a miscalculation will pull the stud out of the head (or worse) -
Re: smokey startup
Just remember that when you put the o'rings on valve stem, be carefull not to damage them on the valve keeper groove. Also, VERY important, compress the valve spring with the retainer on, then put the o'ring in the second groove, below the keeper one. Then install the keepers and release the spring. I have done may heads where the o'ring was put on first and when the valve was compressed the retainer pushed the o'ring down on the valve. They smoked worse than before. I hope this helps.Comment
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Re: smokey startup
i work for a gm dealer and the fix on the newer cars and trucks is both the o-ring seal and the unbrella if you use the gm parts I don't believe you will have any problems done many on late 70 and early 80 corvettes without problemsComment
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Re: smokey startup
If your car has an automatic,your smokey startup may be the result of a leaky vacuum modulator valve on the transmission. I would check this first.Comment
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