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When I have my at/above approx. 5000rpm I notice that the engine sucks oil into the air cleaner via the connection to the oil fill tube/lifter valley. It only happens at higher rpm ,none at other times. Is this one of the reasons GM went through so many PCV configurations?
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Re: 63 SHP crankcase vent
Jim, One of my theories is that we blacken the pcv's so we don't loose points. But in doing so that rusts the inside of the new valve and then they don't seal. Or we get cheap and clean the old one and make it pretty and put it on and same thing happens. Try a new replacment PCV and see if the problem cures it self. Then you know what to do. Course I think you know this already. John -
Re: 63 SHP crankcase vent
Jim-----
I don't think that any Corvettes with PCV systems through at least 1982 are immune from the problem you describe. In fact, after 1967 it may have gotten worse.In Appreciation of John HinckleyComment
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Re: 63 SHP crankcase vent
The 1963 PCV system was a one-year-only design where outside air flowed into the crankcase through the oil fill tube, and was exhausted out the vent hole in the back of the block through a tube to the carb base through a PCV valve or a fitting with a fixed orifice. That flow was reversed for '64-up, with the intake side at the rear block vent hole and the "exhaust" side from the oil fill tube to the carb. There had to be a fundamental engineering reason for reversing the flow, and you probably found it.Comment
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Re: 63 SHP crankcase vent
I never had any problem with oil ingestion from the PCV system of my 327/340, including hot lapping race tracks.
I had to redesign the PCV system of my Cosworth Vega twice to come up with a system that didn't pump oil into the air cleaner.
Modern Corvettes have also suffered from oil ingestion through the PCV. It was a significant problem on the early LS6 engine.
Being as how the PCV system in my '63 worked well, I never figured out why they redesigned it. Cost savings? Given that they went back to a valve after using a valveless system for '65 and '66, they must have been looking something, but the '66 design reversed the flow.
I don't know why they just didn't keep the '63 system.
DukeComment
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Re: 63 SHP crankcase vent
I've only had the issue when sustaining high rpm,which frankly, I was only doing in course of an unrelated maintaince check. When going through the gears with shifts at the high rpm level the issue never manifested itself. It did seem , from a common sense point, that the carb. demand for air was taking it from the least restricted source, the oil fill connection, with enough draw to extract some oil from the lifter valley with it. It's all very interesting to me as I continue to self educate on engine design/evolution/performance with the help of the experienced writers on this forum. Thank youComment
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