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Valve timing model

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JeepSaffer View Drop Down
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Joined: 26 Sep. 2014
Location: South Africa
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JeepSaffer Quote  Post ReplyReply Direct Link To This Post Topic: Valve timing model
    Posted: 04 June 2018 at 3:39pm
I've always been interested in the Willys published valve timing chart:



It tells you when the exhaust valve and inlet valve open and close for a particular cylinder in a 2 revolution cycle. Pretty cool. But it's kinda hard to relate what a particular valve set are doing on a particular cylinder because you have to make sure you are looking at the correct stroke in the cycle. Then, to do it across all 4 cylinders at the same time, which are all at different parts of their cycle..... well, you might be a genius and be able to work it out in your head, but I couldn't.

This weekend I wrote a spreadsheet, which plots each cylinder across every degree of crank rotation for a full 720ยบ cycle, then works out whether the inlet and exhaust valves are open or closed at that point. Then by offsetting the cylinders according to their respective stroke, it tells you the position of each valve set for each of the 4 cylinders, for any given degree of crank rotation. It's pretty useful to visualize how the pistons and valves work as a coordinated system.

I've been looking at saved pictures of my engine with the head off, to validate that the spreadsheet works. It's spot on. At #1 TDC, or any known crank angle for that matter, you can see the valves sit exactly where they should across all 4 cylinders.

I've looked at a few pictures of L134 engines with the head off on the web, and it's cool to work out exactly where an engine is sitting in its cycle, based on the position of the cylinders and most importantly the relative position of each valve. It's kinda like a 12 variable barcode, with one variable for each piston and each valve. There is only one possible engine position in 720 degrees of rotation where all of the 12 variables match correctly. 

Its also useful when you have to work the questions in reverse, like "where would #1 piston be if two inlet valves were open and three exhaust valves were closed?"

It took a few hours of work, but it's a handy tool to have...

Has anyone done anything similar?

Mike


1948 CJ2A #204853 in South Africa
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Bruce W View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2018 at 8:02pm
Sounds like somebody has too much time on his hands. Wink You should spend more time actually working on your jeep.              Just Kidding.

  I studied this kind of stuff every spare minute in junior high and high school, and after many years of working with it, it sorta comes natural for me. Some fellas a while back broke down on a road-trip, and when I saw their video (taken in a Wal-Mart parking lot) of the engine cranking with the head off, I knew that the camshaft was out of time. They finally found that the hub of the cam gear was loose in the gear. Big smile  BW
It is NOT a Jeep Willys! It is a Willys jeep.

Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You!

We Have Miles to Jeep, Before We Sleep.
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