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Thread: c90 cam question (again)

  1. #1

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    c90 cam question (again)

    Ok, I read a lot on this forum about the cams available for the c90 I'm presently overhauling. I bought 4 eci cylinders and NFS 9:1 pistons I got a spare cam on hand and I have to make a choice, please help me with your advices...

    531076 cam from the engine (1825 hrs on it) and I measure 0,330" of lift
    it's the 24° overlap cam
    I have 2 overhaul manual with one saying 0.330 lift and one 0.410 but mine is 0.330

    626608 cam (O-200 cam 0 hr on it) grinded for more duration it's the 35° overlap cam and I measure 0.360" of lift.


    What would be your choice?

    Eric

  2. #2
    Jerry Burr's Avatar
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    I would vote for door #1. The 90 cam has a rounder profile and therefore milder valve action. The pointey O-200 cam will give more upper cyl wear per turn. The only way I know to increase duration is to grind the base to effectively widen the lobes. I wouldn't care for that process in an airplane. Jerry B.

  3. #3
    Steve's Aircraft (Brian)'s Avatar
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    I agree with Jerry....Plus I would never, ever....did I say NEVER...use a re-ground cam EVER again in a fresh engine....last one I used lasted 10 hours before the cam lobes went flat and wiped out the lifters...

    Brian..

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    In the overhaul manual, that .410 was a mistake believe it or not.

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    Quote Originally Posted by Jerry Burr View Post
    I would vote for door #1. The 90 cam has a rounder profile and therefore milder valve action. The pointey O-200 cam will give more upper cyl wear per turn. The only way I know to increase duration is to grind the base to effectively widen the lobes. I wouldn't care for that process in an airplane. Jerry B.
    Thanks Jerry,
    in fact, the O-200 cam have visibles rounder lobes than the C-90 one. At least 0,030" have been removed from the base to compensate what was removed at the top, probably 0.030" more to add the additionnal lift. The seller claims that this cam would turn a 54/68 prop at 3900 RPM. I would expect to turn a 74" prop at 3000 RPM with apropriate pitch but I'm not sure now...

    Eric

  6. #6

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    Quote Originally Posted by tempdoug View Post
    In the overhaul manual, that .410 was a mistake believe it or not.

    Hope this is the only mistake

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    Stock exhaust on a c90-8 with a 7440 mac, wide open cruise, my tach shows 2500 with the 531076. It isnt one of the premier tachs out there so could be off a little.

  8. #8
    Mark Lund's Avatar
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    O-200 with ECI Cylinders, standard ECI pistons, 531076 cam, 50 degree air temps, 1200 ft msl, Legend Cub style exhaust (no muffler), McCauley 7148 prop, full throttle = 2525 rpms in flight.

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    I think if you check the power curve charts for both engines, you'll see the C90 puts out more HP. Use the 90 cam

  10. #10
    Roger Peterson's Avatar
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    I have the master for a 530788 at a cam shop in Mpls if you want to use it. Just send in a old cam and have it remade for about $150.00. Have to use straight pipes or a 4 into one exhause. Can't take any backpressure.

  11. #11

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    Thats why continental went to the 531076. For stock exhaust.
    Last edited by tempdoug; 04-29-2011 at 08:21 PM.

  12. #12
    Roger Peterson's Avatar
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    Just mentioned it in case he wanted to make more power

  13. #13

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    Quote Originally Posted by Roger Peterson View Post
    Just mentioned it in case he wanted to make more power
    Thanks I'm interested in the plan if you have it. PM me if you want.

    I think I'll have to sell this spare cam,


    Eric

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