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rev kits

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    northern member Canuc's Avatar
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    Default rev kits

    do you change your lash when running one ? especially on a roller follower why do you need any lash other than say a .005" hot setting just so everything free's up when on the base circle .
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Moneypit (Ray) PS89 run one. Ray has tould me that they have never had a valvetrain failure since running one. I have been interested in one but no dice for the BBF. I think he would be one of the guys to ask about this.
    Jim & Amanda Rich
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    I was thinking of running one. My thought is it would keep the roller on the cam and if it lost a push rod, the lifter would stay in the bore.

    As for lash, I think you need more than that to compensate for valve bounce.

    Tim

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    northern member Canuc's Avatar
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    Question minimum clearance

    River Rat , makes sense to keep the roller on the cam , was told that it will make the roller and bearing last longer , thats why I run one and to keep the lifter in place should the pushrod or rocker fail , not because of rpm I run under 6k . what would you consider a minimum lash for a mech. roller with a rev kit . always wondered why they required so much clearance especially the older grinds . why does a roller need clearance to get up the opening ramp ?
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    There was a topic on here a while back on valve lash. The trend was to less lash than the .026 of days of old. They were saying all valves bounce when they close even with good springs. You needed some clearance to allow for this. Maybe Steel Comp or one of the engine builders will come on here and explain it better.

    Tim

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    northern member Canuc's Avatar
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    thanks River Rat , missed that one . guess like anything else depends on the variables like cam profile , springs , rockers , r's, etc. probably could tighten up a little at a time till it let you know it's not happy . hopefully get some schooling on this here .
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    Default Ramp speed

    A rev kit has little or nothing to do with lash. A rev kit will prolong valve train life. I never leave home with out one...........You can fine tune a cam profile using valve lash, to a certain degree. Tight lash, (within reason) gives you more top end, loose lash, more bottom.........When a cam card indicates a lash, it is that lash, associated with the ramp speed of the lobe, that gives you the desired (advertised) duration. Lift is also affected, but to a smaller percentage. Different grinders suggest different clearance based on their lobe design. You can "fudge' those numbers a bit to achieve the desired results. (top/bottom). I'm sure someone else can explain it in more technical terms............Ray
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    northern member Canuc's Avatar
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    Squirten Thunder did you get your roller cam set-up you were lookin at awhile back ? did you get the rpm you were hoping to get with it ?
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    northern member Canuc's Avatar
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    Ray , what I don't get is if the ramp dicates a clearance within a certain range when the rev-kit takes that up and the lifter is happy why do you need any more than a min. clearance through the rest of the valvetrain ?
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by Canuc View Post
    Squirten Thunder did you get your roller cam set-up you were lookin at awhile back ? did you get the rpm you were hoping to get with it ?
    I think we have desided to go back to an older set-up we ran, the 292H. It was brushing the 80mph # every time out in testing. We tried a solid roller that was on loan and we had to cut weight in the boat to get back where we were. Now we are thinking with the weight lose, going back to the 292H and cutting down the impeller to a A/B from the A we might get to where we need to be 85mph. Now this is all with a .030 429BBF. Ray got us two 460s cores to go along with the other ones we had and we might be able to make one real good one. But the 429 is what I am running now. It worked real good at the Thanksgiving race, except for a third lap fuel problem, that is ironed out now. It was a 3rd place boat that finished 4th.
    So the answer is not yet, but still trying !
    Jim & Amanda Rich
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    steelcomp was here
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    Quote Originally Posted by Canuc View Post
    Ray , what I don't get is if the ramp dicates a clearance within a certain range when the rev-kit takes that up and the lifter is happy why do you need any more than a min. clearance through the rest of the valvetrain ?
    You don't. Most lash requirements are more than necessary, IMO. The valve tip during valve bounce will only bounce away from the rocker, not into the clearance, so lash has nothing to do with allowing for valve bounce. It's been shown that valve bounce can be geatly reduced by closing down on some of the rediculous lash requirements and smooths out the valve train harmionics.
    Last edited by scott foxwell; 12-20-2008 at 08:32 PM.
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    Quote Originally Posted by Canuc View Post
    Ray , what I don't get is if the ramp dicates a clearance within a certain range when the rev-kit takes that up and the lifter is happy why do you need any more than a min. clearance through the rest of the valvetrain ?
    The manufacturer has planned a lash removal into the ramp. If you decrease the clearance too much the portion of the ramp that was designed to close the lash will be opening the valve. This can have a huge effect on performance, as well as a motor that doesn't like to idle below 2K because of decreased vacuum. Using a rev kit doesn't change anything in lash adjustment numbers......




    Quote Originally Posted by steelcomp View Post
    You don't. Most lash requirements are more than necessary, IMO. The valve tip during valve bounce will only bounce away from the rocker, not into the clearance, so lash has nothing to do with allowing for valve bounce. It's been shown that valve bounce can be geatly reduced by closing down on some of the rediculous lash requirements and smooths out the valve train harmionics.
    I agree most lash recommendations are excessive. I also agree that using a rev kit to keep everything taunt reduces valvetrain harmonics. I run valves on the tight side trying to get everything I can out of the valve event with the cam straight up......Ray
    LOUD BOATS SAVE LIVES

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    northern member Canuc's Avatar
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    Steel I think I get the clearance ramp requirement with a flat tappet cam , does it change any with a rev-kit? what is a minimum clearance for a mild solid full roller set-up with a rev-kit ?
    Quote Originally Posted by gn7 If your ran a cammer your odds of finishing WERE ZERO.

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    Quote Originally Posted by Canuc View Post
    Steel I think I get the clearance ramp requirement with a flat tappet cam , does it change any with a rev-kit? what is a minimum clearance for a mild solid full roller set-up with a rev-kit ?
    A rev kit does not alter the cam profile. A ramp remains a ramp, as designed....Ray
    LOUD BOATS SAVE LIVES

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