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Thread: O200 camshaft -- valve overlap / timing?

  1. #1

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    O200 camshaft -- valve overlap / timing?

    Does anyone know the valve overlap / timing specs for the 626608 O200 camshaft?

  2. #2
    Nathan K. Hammond's Avatar
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    Cam Timing in degrees
    C-85 p/n 40584 8-57-49-16 = intake duration 65’, exhaust duration 65’, with 24’ overlap
    C-90 p/n 531079 & 531146 9-56-50-15 = intake duration 65’, exhaust duration 65’, with 24’ overlap
    O-200 p/n 626608 21-58-65-14 = intake duration 79’, exhaust duration 79’, with 35’ overlap

    First Number Intake opens b.t.c.
    Second Number Intake closes a.b.c.
    Third Number Exhaust opens b.b.c.
    Fourth Number Exhaust closes a.t.c.

    C75/C85 lift: .382
    C90/O-200 lift: .410

    nkh

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    Nathan,

    Are the O200 numbers you've listed for the old C90 530788 cam or the O200 cam?

    The 530788 cam (early C90) has a 35 degree overlap, and from what you're saying so does the O200 cam.

    Wouldn't this make the C90 530788 cam very similar to the O200 cam?

    And... then I'd ask why all the 'hype' about the C90 cam (53078 vs. the O200 cam if they have the same overlap?

    Am I missing something??

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    Nathan K. Hammond's Avatar
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    I think you're right.

    These numbers were taken from the latest O/H manual dated 1984, but after looking again, I'm suspicious of the O-200 numbers. They indicate the early model 35' degree overlap, instead of the 24' degree model.

    sorry for the mix up.

    nkh

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    I wonder if.....

    I wonder if the higher overlap camshaft could be legally used on ANY 0-200? Using this camshaft would effectively move the peak torque to a much lower rpm, where you could use the power, not at 2700rpm, where you would almost never see? The real advantage of the C90 over the 0-200 is that it makes much more power at a lower (usable) rpm.

    Mike

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    So I wonder if anyone can confirm with certainty what the O200 camshaft specs actually are?


    Quote Originally Posted by Nathan K. Hammond
    I think you're right.

    These numbers were taken from the latest O/H manual dated 1984, but after looking again, I'm suspicious of the O-200 numbers. They indicate the early model 35' degree overlap, instead of the 24' degree model.

    sorry for the mix up.

    nkh

  7. #7
    Jerry Burr's Avatar
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    Cam specs

    I went through this a while back. The Overhaul Manual is wrong! There are several ways to degree a cam. The manual doesn't say what method Continental used. Jerry B.

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    A friend of mine has gone through this process for the C90 / O200 cams. I'll see if I can get his data.

    It would be interesting though to see Continental's specs on the O200 cam. They've got to be around somewhere.

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    It is possible to turn 2700 with an O-200 during climbout, using a flat prop. You can still get decent cruise speed because of the higher rpm capability of the O-200.
    JimC

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    0-200 camshaft

    According to my degree wheel and math the 0-200 cam using the opening and closing numbers posted is 259 degrees duration on both intake and exhaust with lobes centered @ 107.5.degrees.

    Jerry is correct in that cam measuring specs can be given in a couple different ways.Measurements are sometimes given at a certain amount of tappet or valve lift,say .050".

    There is a lot to camshafting,more than just a few numbers.Lobe profile is one.A cam lobe has a point where it begins to lift,a peak and a closing point but the ramp profile in between can have many variations.

    An example would be in Stock class racing.The lobe must meet the factory opening and closing and max lift spec but the ramps between can be much more aggressive.This opens the valves at a quicker rate and delays the closing in the same way.The lobe profile looks nothing like a stock cam but when degreed it will check to the same spec.Very hard on valve springs but huge power !

    There is no doubt in my mind that a better cam,not a radical one but a better one would really wake these little engines up.Try talking to Continental about it if your up for an exercise in frustration.They were not even willing to give specs to me ,told me it was proprietary info.I asked if they knew what a degree wheel and dial indicator were used for.

    No one needs to know what cam you run.Think like a racer,play dumb!

  11. #11

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    Is there any after market cam manufacturer, or builder, doing any development work on cam profiles for either continental or lycoming 4bangers? In these day of cad/cam I would think someone would be working on it.

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    0-200 camshaft

    Lycon could probably tell you if anyone is currently doing other than stock cam profiles.

    Any cam manufacturer has the ability to run a theoretical profile and grind it.Having a core with enough material to allow for a profile change would likely be a problem.Making a complete cam from a billet would be the only way to do it in that case.

    Increasing rocker arm ratio is another way to gain a little cylinder filling without getting into the case.There are things like valve to piston clearance,spring coil bind,pushrod tube space,rocker stand strength,rocker cover clearance,just to point out things that must be considered.

    What I would do is look for more torque.Intake tube length and volume are variables that can greatly affect the torque output and curve.
    This is the same as the tuned exhaust principle.

    The intake and exhaust flow moves to and fro in the pipes in a pulsing manner.Think of it like a slinky.What you want to achieve is to get the flow in a rhythm with the valve timing so it fills the cylinder with as much fresh fuel and air as possible in the time allowed by the open valve.Tube size and length affect velocity and that affects time and the timing of the pulse cycle.

    Some times a length change of 1/4-1/2 inch can make a noticeable change.I have used a 2" spacer under a carb to change the length of the whole system.Different size spacers where the intake flange meets the cylinder would be easy to fabricate.Install some long studs and try some different ones.Longer tubes could be made quite easily.Remember tube size/volume and length go hand in hand.

    Lots of these engines do not have equal length runners either.This is mostly done for cost and ease of manufacture.

    A good source for this type of stuff is Society of Automotive Engineers website.

    Hope I didn't bore anyone.I love this stuff.Finding more power has always been fun. Bill

  13. #13
    Steve Pierce's Avatar
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    They have a cam doctor that they use to check the profile on different manufacturer's cams. I can't remember which one was better. Competition Cams in Memphis ground one for an O-320.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    With all the pylon racers in that one class running those O-200s, none of them must have a cub. Ive never seen any chime in here. I know its a different game they play with the high rpm,s and style of aircraft. But theyed be the ones that would know what would keep a 200 purring or not. Anyone familiar with any of those guys. doug

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    Right on, Bill.
    JimC

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    I've heard that intake valves from a 520 will really perk up an O-200, but that they also make the cylinders far more subject to cracking.
    JimC

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    0-200 camshaft

    Boring the intake pocket to install the big valve probably leaves too little material.Small block chevy did the same with 2.02 valve

    Something in human nature says bigger is better.Winston Cup engine builders learned that an intake manifold with bores SMALLER than the restrictor plate Nascar supplied actually flowed better because it kept the airflow in the center of the carb bore and away from the protruding restrictor plate.

    The cylinder head design of these aircraft engines is junk.Right angle port entry and exit is about as bad as youcan get.An 0-200 has a round intake tube to a 90 degree elbow to a rectangular port to a round valve.Take a piece of u-channel and lay that out and try to flow water through it.
    Air has mass and it does not like sharp bends,and shape changes.All the same things an airfoil is subject to apply here.
    A straight forward thing like cyl castings with a better port angle would give tremendous gains.

    Volumetric efficiency is the term that applies here.
    Oh and don't bother trying to polish intake spiders,tubes or ports.A better finish is sandblasted or like a 36 grit paper would leave.The smooth polished surface promotes fuel puddling.Rough shreds the fuel droplets promoting better exposure to the oxygen resulting in more complete combustion.
    Cars, motorcycles,jet skis,airplanes,they all respond to physics.

    Bill

  18. #18

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    Yeah, I make my living doing fluid mechanics. I agree. My hunch is that with an appropriately designed spider, intake elbow and intake port, the O-200 would do better with a smaller intake valve -- but, with the present design, I suspect a larger valve that opens faster might do better than the stock valve. For esthetic reasons on J3's, I wouldn't want to change the external appearance too much. I do like to rework the interior of the spider, but do not polish it.
    JimC

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    Interesting thread.

    At the end of the day all I'm after is an apples to apples comparison of the C85 cam, the C90 cams and the O200 cam.

    If we could get Contental's data that would be a good start.

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    I think you'll wind up having to get a cam shop to pull the profiles for you.
    JimC

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    0-200 camshaft

    Tomorrow I will call Continental and see what I can get for info on these cams.Maybe I can find someone helpful.I will keep you posted.

    Bill

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    Excellent, I'm looking forward to seeing some numbers from Continental.

    This camshaft talk is interesting but I've yet to see any hard data to really explain the all the differences.

  23. #23

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    0-200 camshaft

    OK here it is right from Continental.I got a guy that really wanted to help.

    The numbers posted above as far as opening and closing points are correct.

    The C-90 and 0-200 both are.410"lift cams.

    The C-90 is 245 degree duration on both Intake and Exhaust with a 24 degree overlap.

    The 0-200 is 259 degree duration on both Intake and Exhaust with a 35 degree overlap.

    The C-90 cam will produce it's peak torque at a lower rpm due to it's shorter duration and overlap.

    The 0-200 cam will produce more power up top.That said ,there is no reason to run the C-90 cam in an 0-200 UNLESS you are limited to the rpm you are allowed to turn by STC .

    Continental built the 0-200 for the Cessna 150.it did not have the ground clearance to run a 74" prop like a Cub or other tailwheel aircraft.The only way to get the needed thrust with a short prop was to cam it so it could be spun higher.

    My 0-200 turns 2600 with the brakes locked.I cruise 2550@5gph leaned and see 92 mph.That is with a 75-35 prop.I think the 75-38 would be perfect.And a 0 thrustline works as well on an 0-200/cub as it does on a Supercub! Hope this answers your question. Bill

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    Did you happen to ask him about the old C90 cam (53078??

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    0-200 camshaft

    He gave me the specs for all the cams he had listed.To the best of his knowledge the C-90 specs that I just posted are for that cam.
    He went all the way back to the 75.

    If anyone has any of these old cams laying around and wants to send them I will check them on a cam doctor and post results.Cam does not have to be useable just a couple good lobes. Bill

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    Re: 0-200 camshaft

    The 530788 cam is definitely different, it has visibly 'fatter lobes'. I'm still waiting on my friend to send me his measurements.

    Probably very hard to find one of these things just laying around.


    Quote Originally Posted by willyb
    He gave me the specs for all the cams he had listed.To the best of his knowledge the C-90 specs that I just posted are for that cam.
    He went all the way back to the 75.

    If anyone has any of these old cams laying around and wants to send them I will check them on a cam doctor and post results.Cam does not have to be useable just a couple good lobes. Bill

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    0-200 camshaft

    I spoke to Don Swords this morning.The specs Continental gave me were for the 176 cam.Don said they won't give the 788 specs.He did not have the specs in front of him but did say the 788 has 35 degrees of overlap and the opening and closing specs are different from the 176.

    I also spoke to Competition Cams about doing a regrind and they said it usually runs about $ 125.They would need a core and the specs you wanted or they could develop a profile. Bill

  28. #28
    Roger Peterson's Avatar
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    Still no numbers for the 788 cam. I have a new one at home on the shelf. When I get home in the fall, will take it to the cam shop and have them run a profile. If anyone wants one, can have them run sum at that time.

    It sure made my 0-200 run different.
    Roger
    Based at O8XS. Sweeny Texas (Winter)
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    I plan on living forever.......so far, so good !!!

  29. #29
    Chris in Idaho's Avatar
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    Did you ever get a chance to run a profile on the 788?

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    Roger Peterson's Avatar
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    They use a different system so their mfg data was no help to me. Have had a couple made.
    Roger
    Based at O8XS. Sweeny Texas (Winter)
    Finlayson Lake, Ontario (Summer)
    I plan on living forever.......so far, so good !!!

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    O-200 Camshaft

    Maybe somebody can help to find my peace after a lot of years, asking hundreds of so called experts and after paying 12k$.......
    years ago I rebuild my 2nd PA-18 with a O-200, 0h, freshly overhauled in the US and shipped to Germany. It was mounted in and right the 1st test run showed an abnormality, at full throttle 2100 RPM the engine was running rough and was shaking & stuttering. When I pulled the mixture a little bit it ran smooth and ground RPM was about 2150 with temps in the green arc. Changed Carburetors with different settings, Propellers with different pitch, checked the Primer pump, the gap in the air box, fuel flow, valve springs, mag's etc. nothing at all...............
    I contacted the deliverer in the US, with a few words, the 2 brothers at E........ton refused the warranty. I flew the PA-18 for some 150h and finally I had to take off the engine, replace the 2 burned cylinders and it was converted to a C-90-14F and it ran fine after.
    I never found out the reason of that symptom, not even the shop who did the conversion could explain that. My thought was, that there was mounted a wrong camshaft as for an engine for industrial use or similar. even if the Camshaft showed the right P/N according the Overhaul manual. Now, after years, reading about the valve overlapping due to a wrong Camshaft.... this could be the reason why!
    Had somebody had same or similar problems????

  32. #32
    behindpropellers's Avatar
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    Who rebuilt the engine?
    Piper J-5A C-90 N40877
    J-5 Project Pictures

  33. #33

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    1st time was rebuild in the US, a shop at Elisabethon and 2nd time near Frankfort/Germany.
    The C-90-12F of my 7-EC and the O-320 PA-12 were rebuild by Ole Joergensen, Padborg/Denmark, never had any problem with them

  34. #34

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    O-200....full throttle....2100rpm?
    I'll bet if I had a prop on my O-200 that only let it turn 2100rpm static that it would be very unhappy.....
    I would suspect that the C90 cam would be happier at that static rpm (but it still seems pretty low ...)
    DaveG
    DaveG
    Exp Cub N118DG

  35. #35

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    ............can you imagine how unhappy I was, due to a new, never running as should engine & never making more RPM.........

  36. #36

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    reviving old thread here...does anybody know where you can get dimensions of the 0200 or c85 rockers..or does anybody know the ration of these

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    Just saw this old post. Rocker ratio is 1.2

  38. #38

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    What about the new O-200 cam 643067?

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