Increasing Rocker Ratio.....
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From: san antonio
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with mr. max's formuli, you could go to cam sites and find what cams they offer without any head work and see what total lifts would be and if yours falls below, probably good to go. it is a lot of work to check distance on an assembled engine.
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Joined: Jun 2006
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From: san antonio
Don't disagree with bustert as it is a lot of work to actually measure valve to piston clearance on an assembled motor. However, in this case (if it were me) a piece of .060" solder through the spark plug hole would tell me all I needed to know. If the OP has plenty of clearance as he thinks he does, the solder would be likely be untouched and would confirm that the OP does have all the clearance needed. Just a simple step to put the clearance issue to bed. Having said that, if the OP gets that same level of comfort from cam specs, math, etc., then I suspect he won't bother with any additional checking.
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From: Poolville
Don't disagree with bustert as it is a lot of work to actually measure valve to piston clearance on an assembled motor. However, in this case (if it were me) a piece of .060" solder through the spark plug hole would tell me all I needed to know. If the OP has plenty of clearance as he thinks he does, the solder would be likely be untouched and would confirm that the OP does have all the clearance needed. Just a simple step to put the clearance issue to bed. Having said that, if the OP gets that same level of comfort from cam specs, math, etc., then I suspect he won't bother with any additional checking.
Thanx Scott, I calculated .626" lift with the 1.725 rockers. My biggest concern is moving my torque to the right. I like where it currently is. I have 100 lbs of torque by 2800 rpm and 110 by 3300 rpm and can maintain 100 lbs up to 5300rpm... Not bad for a 96" Evo.. I will call Crane in the morning.. Thanx... I made a mistake earlier when I calculated my tdc lift, intake is .2155" and exhaust is .1965". It's really not that far off of the W9B. 2* less on the LSA and 6* less on the ivc, which is only a calculation using the 1.725" rockers...
Last edited by 98hotrodfatboy; Feb 4, 2019 at 06:04 PM.
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From: Poolville
Cams are speced at 0.053 tappet lift as stated so you won't see that spec change but overall duration will.
With a 0,053 lifter spec, the valve is at 0.053 x 1.625 = 0.086 at 0 lash (assume hydraulic lifter). If you add 1.725 rockers, the calve lift is 0.053 x 1.725 = 0.091 so the valve is lifted higher. Working back to what duration you could get compared to a 1.625 rockers you need to take the 0.086 and divide by 1.725 = 0.050. On measurement it works out to about 2-4 degrees.
With a 0,053 lifter spec, the valve is at 0.053 x 1.625 = 0.086 at 0 lash (assume hydraulic lifter). If you add 1.725 rockers, the calve lift is 0.053 x 1.725 = 0.091 so the valve is lifted higher. Working back to what duration you could get compared to a 1.625 rockers you need to take the 0.086 and divide by 1.725 = 0.050. On measurement it works out to about 2-4 degrees.
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From: poway
I'm starting to understand. So @ .053" lift at the lifter with 1.625 ratio rockers I will have that same lift at .050" lifter travel because of the 1.725 ratio rockers... and that difference in lift is actually a difference in degrees... Am I correct in the way I'm thinking? Based on that I can see the change in valve opening but to me the most important is that even by adding a degree to both the opening and closing of the valve, it still will not change my LSA... Sound right?
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From: Poolville
I think I'm gonna do it.. I'll let you guys know if I feel any difference... I know the only way to tell is by a dyno but I'm starting to run out of money.. We'll see what spring brings... Thank you to every one.. I truly appreciate your knowledge and have a better understanding of the change in ratios... I will update later in the year.... One more question, I only see S&S are there others I should consider?... Thank You.....
Last edited by 98hotrodfatboy; Feb 4, 2019 at 06:50 PM.
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From: Alorton, Illinois
Originally Posted by 98hotrodfatboy
I'm starting to understand. So @ .053" lift at the lifter with 1.625 ratio rockers I will have that same lift at .050" lifter travel because of the 1.725 ratio rockers... and that difference in lift is actually a difference in degrees... Am I correct in the way I'm thinking? Based on that I can see the change in valve opening but to me the most important is that even by adding a degree to both the opening and closing of the valve, it still will not change my LSA... Sound right?