Rocker Geometry Problems .100 longer valves
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Rocker Geometry Problems .100 longer valves

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    Member phil369's Avatar
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    Default Rocker Geometry Problems .100 longer valves

    Have a set of 049 BBC iron heads, replaced valves with Manley severe duty valves, machine shop said he needed the longer valves to get seat pressure correct. Now all valve events are out the window, rocker riding on outside, exhaust side of valve. Have adjustable push rods for mock up, can shorten them until rockers touch retainers, still valve timing events are screwed up. Have the crane gold rockers, 1.7 ratio, is ,my only option to run the crower backset
    rockers to correct geometry? If I get the backset rockers, do I still run the 1.7 ratio? Cam is a lunati solid roller, used the recommend springs, retainers & locks from lunati? Thanks in advance for the input. Phil

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    Senior Member EdonShano's Avatar
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    Quote Originally Posted by phil369 View Post
    Have a set of 049 BBC iron heads, replaced valves with Manley severe duty valves, machine shop said he needed the longer valves to get seat pressure correct. Now all valve events are out the window, rocker riding on outside, exhaust side of valve. Have adjustable push rods for mock up, can shorten them until rockers touch retainers, still valve timing events are screwed up. Have the crane gold rockers, 1.7 ratio, is ,my only option to run the crower backset
    rockers to correct geometry? If I get the backset rockers, do I still run the 1.7 ratio? Cam is a lunati solid roller, used the recommend springs, retainers & locks from lunati? Thanks in advance for the input. Phil
    get ahold of STEELCOMP here on the boards...does wonders with heads...
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    Member phil369's Avatar
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    Waiting on his reply, one of the most trusted people for this advise in my opinion. There are a few more, I live on the wrong coast, or he would be doing my heads, & I wouldn't have these problems!!

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    steelcomp was here
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    Quote Originally Posted by phil369 View Post
    Waiting on his reply, one of the most trusted people for this advise in my opinion. There are a few more, I live on the wrong coast, or he would be doing my heads, & I wouldn't have these problems!!
    Thanks Phil. If you want to give me a call, I'll try to talk you through it. 805 350 1159.
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    Bostick Racing Engines six-oh-nine's Avatar
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    Seems like with the available springs, different offset retainers, and offset locks, that unless you are trying to run something way out of the ordinary, or some big lift roller, that you should have been able to find something that would have work without going to longer valves.

    That all being said, the Crower backset rockers can get you back into getting your geometry correct and not having the roller run off the end of the valve. They have two offsets, a .050 and .090... you can get them in any ratio that they make bodies for (1.55 all the way to 1.8), but you will for sure want to figure out your pushrod length with the rocker you intend to use. And do not do the "middle of the valve" method of determining you pushrod length, valve and rocker being at 90* to each other at half lift is what you're gonna want to shoot for... the rocker tip riding in the middle of the valve is nice, but seldom actually works out... but rolling off the edge is certainly a good time to get some backset rockers.
    Last edited by six-oh-nine; 09-29-2012 at 04:25 PM.
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  8. #6
    www.highflowdynamics.com LakesOnly's Avatar
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    Quote Originally Posted by phil369 View Post
    Have a set of 049 BBC iron heads, replaced valves with Manley severe duty valves, machine shop said he needed the longer valves to get seat pressure correct. Now all valve events are out the window, rocker riding on outside, exhaust side of valve. Have adjustable push rods for mock up, can shorten them until rockers touch retainers, still valve timing events are screwed up. Have the crane gold rockers, 1.7 ratio, is ,my only option to run the crower backset
    rockers to correct geometry? If I get the backset rockers, do I still run the 1.7 ratio? Cam is a lunati solid roller, used the recommend springs, retainers & locks from lunati? Thanks in advance for the input. Phil
    If your valve train geometry was optimized before the cylinder head work and there are no other changes whatsoever in your engine combo except for the +0.100" longer valves, then you need longer pushrods, not shorter pushrods.

    Sounds like you are trying shorter purhrods in an attempt to move the roller wheel back to the center of the stem tip. But where the roller rides on the valve tip has nothing to do with valve train geometrics and if you concern yourself will trying to get that roller wheel on the center of the valve stem then you are likely doing so at the exepnse of good valve train geometry.

    The roller has been repositioned outboard on the valve stem tip only because the tip of the taller, +0.100" valves is closer to the rocker stud than the standard length valves. Yes, ideally you want to have the roller on the center of the stem but technically speaking as long as the entire footprint of the roller wheel is atop the valve throughout the radial sweep of the rocker arm then you are okay, mechanically speaking. Then just you turn your attention toward optimizing the valve train geometry and let the roller tip ride wher it may.

    The primary purpose of the roller tip is to provide a second pivot point so that the downward forces of the rocker arm action remain in-line with the valve stem as the rocker arm moves through its radial sweep, so don't worry about premature guide wear with the outboard roller wheel. Frankly you are far more likely to experience guide wear from a poor valve train setup with a centered wheel than good valve train geometry with the roller tip outboard on the valve.

    Start lengthening (not shrotening) your pushrod checker to compensate for your +0.100" valves. If you are using shelf pushrods then those that are about 0.050" longer than what you had with the standard length valves will get your geometry closer to where it was, since 0.100" / 1.70 = 0.058"


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    Last edited by LakesOnly; 09-29-2012 at 05:43 PM.
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