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Thread: cam advance/retard on a 2.5

  1. #1
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    cam advance/retard on a 2.5

    I have a FM475 cam on my engine with an adjustable cam gear, what's the best way to set it up? I was thinking
    of doing a compression test and tweek it to get the best compression or do I run the engine and tweek it to get
    the best vacuum?. My car still failed emissions and the only thing left to check is the cam setting.

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    Buy my stuff!!!!!!!!!!! :O) Turbo Mopar Vendor turbovanmanČ's Avatar
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    Re: cam advance/retard on a 2.5

    The old school way is to maximize compression via cam timing, that gives you the best idle and bottom end but sacrifices top end power, but I would find out where its supposed to be set and go from there.

    I thought those cams were fairly tame? What were/are your readings? Set up? Cat?
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
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    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: cam advance/retard on a 2.5

    What's failing it? I'd be a little surprised if the cam phasing is what's causing it, but you never know...

    Mike
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  4. #4
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    Re: cam advance/retard on a 2.5

    Quote Originally Posted by turbovanman View Post
    I thought those cams were fairly tame? What were/are your readings? Set up? Cat?
    The cam is mild, shouldn't be an issue unless its way off the mark.

    I hope this picture of the readings are large enough to read. The top one is last week WITHOUT a cat, the bottom is with a cat and timing backed off to 8 degrees, just when it started running rough.

    On the adjustable cam sprocket, please finish this sentence. Turning the sprocket clockwise _______________ the cam.

    Click image for larger version. 

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  5. #5
    turbo addict
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    Just do the same as the top one with the cat.
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

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    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: cam advance/retard on a 2.5

    Turning clockwise advances it. I had 19" of vacuum at idle on my 2.2 swirl w/ an FM475 cam installed straight up (stock gear).
    Rob M.
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  7. #7
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    Re: cam advance/retard on a 2.5

    ^15" is what I have now, will be curious what I come up with after messing with it.

  8. #8
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    Re: cam advance/retard on a 2.5

    I have my f475 idling at 18-19"vac
    i would pull some fuel and add some timing in that spot just to get it to pass then switch it back if needed

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    Re: cam advance/retard on a 2.5

    Your too rich at high idle-sic, the CO is 1.99, it should be .5 ish. You need to take out some fuel or go back to this setting and put a cat on, it will read 0's across the board.
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

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  10. #10
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    Re: cam advance/retard on a 2.5

    Well I advanced the cam about 3 degrees and have 19-20" of vacuum and the car is noticably smoother.

    How do I set it up for performance, just run it down the track, tweek it, and run again?

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    Re: cam advance/retard on a 2.5

    Quote Originally Posted by fishcleaner View Post
    Well I advanced the cam about 3 degrees and have 19-20" of vacuum and the car is noticably smoother.

    How do I set it up for performance, just run it down the track, tweek it, and run again?
    Read my first post,

    Track time or a dyno is the only true way of figuring it out.
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

  12. #12
    The moderately moderate moderator Turbo Mopar Staff
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    Re: cam advance/retard on a 2.5

    Quote Originally Posted by fishcleaner View Post
    Well I advanced the cam about 3 degrees and have 19-20" of vacuum and the car is noticably smoother.

    How do I set it up for performance, just run it down the track, tweek it, and run again?
    Definitely a good place to start.
    Bryan
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  13. #13
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: cam advance/retard on a 2.5

    Dont adjust it for best compression numbers at 300 rpm. That is not a good idea. If you take the schrader valve out of the compression tester you can do a running compression test and try to get the best numbers at the RPM where you actually WANT to make power, but that rpm is definitely not 300.

    Dont push the red button.You hear me?

  14. #14
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    Re: cam advance/retard on a 2.5

    Quote Originally Posted by Vigo View Post
    Dont adjust it for best compression numbers at 300 rpm. That is not a good idea. If you take the schrader valve out of the compression tester you can do a running compression test and try to get the best numbers at the RPM where you actually WANT to make power, but that rpm is definitely not 300.
    Why do you say that? Setting cam timing by compression is an old trick that's been around since the dawn of time and it works. It will give you maximum off idle and midrange performance.
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

  15. #15
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    Re: cam advance/retard on a 2.5

    Well I did the compression test all cylinders were between 175-180 before bumping the cam ahead then it was 205-210. Throttle response was good but top end was noticably sacrificed, I'm leaving it there for the emissions test. Vacuum was still 19-20" no improvement.

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    Re: cam advance/retard on a 2.5

    Quote Originally Posted by fishcleaner View Post
    Well I did the compression test all cylinders were between 175-180 before bumping the cam ahead then it was 205-210. Throttle response was good but top end was noticably sacrificed, I'm leaving it there for the emissions test. Vacuum was still 19-20" no improvement.
    Exactly what the result should be. I would maybe venture to say retard the cam timing until the compression stops dropping, note that degree and split it between the best advanced timing,
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

  17. #17
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    Re: cam advance/retard on a 2.5

    ^ stops dropping? or starts dropping

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    Re: cam advance/retard on a 2.5

    Advance until you get maximum compression, retard until you the compression stops dropping, pick the middle. This is simply a guess proceedure, lol.
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

  19. #19
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    Re: cam advance/retard on a 2.5

    gotcha, I'm at the max compression now. Man is it so much easier tweeking the cam gear as apposed to V8's and the offset spacers.

  20. #20
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: cam advance/retard on a 2.5

    been around since the dawn of time and it works. It will give you maximum off idle and midrange performance.
    Thats why i would never do it.. Generally the stock setup is as far biased towards off-idle performance as im willing to go. The 4000+rpm powerband on these things already sucks without making it worse.. lol

    Dont push the red button.You hear me?

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