Retard cam - Reversion issue
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Retard cam - Reversion issue

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    Member Tahoe540's Avatar
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    Default Retard cam - Reversion issue

    I have my motor out for some winter upgrades and it looks like I am getting some reversion? I installed my cam 2 degrees advanced but would like to retard it as I am not running 11:1 compression and would like a little more rpm on the top end. I have Imco powerflow exhaust and have been told these are not the best for reversion. Attached is my cam card and some exhaust pics. Would retarding it back to straight up or even a degree or two retarded make that much difference? Engine in a 548 10:1 BBC with 088 heads. Click image for larger version. 

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    Senior Member SoldHondaBoughtHondo's Avatar
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    Been told anything more than 255 @ .050 is the beginning of problems.
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    steelcomp was here
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    I see signs of a little moisture but don't see anything that looks like reversion.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    I was going to post the same thing Scott.

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    Member Tahoe540's Avatar
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    Quote Originally Posted by scott foxwell View Post
    I see signs of a little moisture but don't see anything that looks like reversion.
    Thanks for the responses. This is my first boat and have the motor apart for some upgrades and had some people warn me about reversion issues. What would reversion look like, worse?

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    Senior Member wagspe208's Avatar
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    UH...I think it is "developmentally charged" camshaft.
    HATER

    fuck...challenged

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    Quote Originally Posted by Tahoe540 View Post
    I have my motor out for some winter upgrades and it looks like I am getting some reversion? I installed my cam 2 degrees advanced but would like to retard it as I am not running 11:1 compression and would like a little more rpm on the top end. I have Imco powerflow exhaust and have been told these are not the best for reversion. Attached is my cam card and some exhaust pics. Would retarding it back to straight up or even a degree or two retarded make that much difference? Engine in a 548 10:1 BBC with 088 heads. Click image for larger version. 

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    Single pattern cams will work with AFR headed BBC engines, they are not optimal with OEM heads and will suffocate the engine. I'd be willing to guess she hits an rpm wall and won't pull past that given rpm not matter the prop change.
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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    Quote Originally Posted by cstraub View Post
    Single pattern cams will work with AFR headed BBC engines, they are not optimal with OEM heads and will suffocate the engine. I'd be willing to guess she hits an rpm wall and won't pull past that given rpm not matter the prop change.
    In a sense you kind of explained my summer trying to get this boat moving on a high altitude lake (6200 ft). The engine dyno'd at 621 hp and 675 ft lbs. at 5400 rpm but could not get anywhere near 5k rpm with more than an 18 pitch prop. I am really thinking about getting a new cam ground as I am not ready to buy new heads or buy 5k headers. This cam was reground from what I got as a project boat. I recognize both you and Scott Foxwell from my past days of drag racing and seeing you on those forums. So you do custom ground marine cams?

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    steelcomp was here
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    To answer your question for Chris, yes he does custom cams. Has done plenty of marine cams.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    steelcomp was here
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    Thanks for the responses. This is my first boat and have the motor apart for some upgrades and had some people warn me about reversion issues. What would reversion look like, worse?
    Yes, it would be a lot worse. You might have water in the oil as well.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    Quote Originally Posted by Tahoe540 View Post
    In a sense you kind of explained my summer trying to get this boat moving on a high altitude lake (6200 ft). The engine dyno'd at 621 hp and 675 ft lbs. at 5400 rpm but could not get anywhere near 5k rpm with more than an 18 pitch prop. I am really thinking about getting a new cam ground as I am not ready to buy new heads or buy 5k headers. This cam was reground from what I got as a project boat. I recognize both you and Scott Foxwell from my past days of drag racing and seeing you on those forums. So you do custom ground marine cams?
    I've seen your you "situation" many times. I have tried to explain in on other boat forum's only to be banned because of politics. Yes we do quite a bit of marine stuff each year. If you need some help let us know. The high elevation adds to the cam design but nothing I haven't had to deal with in the past.
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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    Thanks Chris I will be getting in touch with you soon. Dropping off my heads today to get exhaust seats checked as I had some exhaust leaks during a leakdown test before teardown. If things aren't good I will be forced to buy new heads (which I would not mind doing).

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    Quote Originally Posted by Tahoe540 View Post
    Thanks Chris I will be getting in touch with you soon. Dropping off my heads today to get exhaust seats checked as I had some exhaust leaks during a leakdown test before teardown. If things aren't good I will be forced to buy new heads (which I would not mind doing).
    After market heads will require a smaller cam to make power. This will give the engine better manners at low speed driving. Will make for a flatter power curve.

    This is a a pump gas, under 9.5 to 1 compression 509CID with a set of the ProMaxx heads that we machined here for marine use. Cam is mid 600 lift and low 250 duration. At last conversation customer was spinning a 26P Bravo on the drive and was in the low 90's in the boat.
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    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

  16. #14
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    She made 677HP at 6000 rpm and over 600#/ft
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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