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1. 06:00 AM - Re: Lycoming Cylinder question (Gary Casey)
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| Subject: | Re: Lycoming Cylinder question |
I'm not "the" Lycoming expert, but as far as I can tell everything
with a power rating of 300 or more has the angle-valve cylinders. A
sure-fire way to tell is to look at the Lycoming spec sheet on their
website and the parallel-valve engines are narrower. Other than that
the model numbers don't give much of a clue unless you just know
which is which. As Bill said, the angle-valve heads flow better.
The naturally-aspirated versions have a 8.7 compression ratio vs. the
8.5 of the parallel-valve engine, and that also helps to produce
slightly more power. With more space between the valves the angle-
valve engine requires less pressure drop for cooling, theoretically
reducing cooling drag. But they are heavier, to the tune of 4 or 5
pounds per cylinder and the angle-valve engines don't have the same
reputation for longevity as the parallel-valve engines. An expert
told me that there is nothing to be gained by porting and polishing
the angle-valve cylinder, while the parallel-valve version can be
ported to achieve almost the same airflow as the angle-valve cylinder.
Gary Casey
Parallel-valve IO-540 with 10:1 compression dyno tested at 305 hp
> From: Dan Rogers <drogers@maf.org>
> Subject: Engines-List: Lycoming Cylinder question
>
>
> I have some questions about Lycoming Cylinders. I understand that all
> their 360 and 540 engines use the same size cylinders. Also that
> there
> are 2 types of cylinders: Straight valve and Angle valve. I know what
> the cylinders look like and can easily tell the difference but what
> are
> the differences in engine application? How can you know whether a
> IO540
> L (for example, if there is such a thing) has one or the other type of
> cyl? Do the high HP engines have one type and the Lower hp the other
> type? Is one type of cylinder newer than the other?
>
> Thanks,
>
> Dan
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