Quote:
Originally Posted by Hib Halverson
Our LT5s do indeed have flat tappet camshafts, but the none of the alarmist beliefs about flat tappet cam and lifter wear apply to our engines, because they use flat tappets and direct-acting bucket tappets rather than pushrods and rocker arms.
Yes, an LT5 has flat tappet cams, but its cam lobes are much wider than those you'd find on a camshaft in a pushrod V8, thus the load bearing area on the lifter face which is swept by lobe as the cam rotates is greater. In addition, our engines do not have the higher loads at the lobe/lifter interface which are typical of pushrod and rocker arm valve trains.
Bottom line: the loads are far less and because of the width of the LT5 lobes, that less load is spread over a greater area.
Engine oils which meet or exceed the old GM 4718M (previously applied to 93-95 LT5s) or the current "Dexos 1" specification will provide more than adequate lubrication of the LT5 valve train. No special engine oils or fortifying additives are necessary.
That said, no harm will come to the engine if one chooses to use an engine oil with higher zinc/phosphorous content as long as the phosphorous content does not exceed 1600 ppm. Long term use of an engine oil with more "ZDP" than 1500-1600-ppm is likely damage your engine.
Those who use one of the many "ZDDP", "ZDP" or zinc additives need to be cautious with such productds. Few of them specify their ZDP content, thus, it's impossible to know how much more zinc your putting in your oil. Some of those additives can be 10% or more (that's 100,000+ ppm) ZDP.
With ZDP, the belief "if some is good more is better" absolutely does not apply. Over 1600-ppm phosphorous for extended periods will cause engine damage, so...buyer beware.
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yup. with the really nice hard cams, big cam lobes (wide), huge direct acting lifters, and small light valves with light valve springs we're not dealing with 240 lbs of seat pressure with a pushrod engine that will wipe the cams real ez.
the LT5 valve train is pretty bullet proof and wears really well with decent and clean oil. the really high amounts of zinc will do more to "kill the cats" than it will help the engine.
other than a few bad batches of "soft" cams (aftermarket) stock LT5s typically don't have much in the way of valvetrain problems.
we just pulled apart an LT5 with only around 30k miles on it and the lifters and cams almost looked new. very little wear at all.