FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: spookie on January 06, 2019, 06:09:14 AM
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I have been told if my sbc N/A on alcohol runs faster with headers verse zoomies I should switch to 1.6 rockers on exhaust valve.My fed did pickup .03 to .05 with headers. This is same day testing,a-b-a.Would 1.6 rockers help or have I met someone just with rockers to sell? I bracket race and will not remove the zoomies!!!!
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Reasoning?
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I don't get the reasoning for that either ! You might see a gain by putting a 1.6 on the the intake side but it would have little to do with headers !
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As a suggestion, see if the fella with the rockers will let you run 8 on the exhaust and buy them if the car runs quicker in A-B testing. If they don’t, return them to him. I’d be interested to know the results.
As to if this would work, I think it might. But that all depends on what you have for a cam right now. Reasoning? Replace the headers with zoomies and you lose the wave and inertia scavenging the headers produced by way of the length of the pipes and the collectors. Your engine is now down on power, just as your testing proved. One way of getting some of that lost power back is to get rid of more exhaust gases quicker to help overcome the current lack of wave scavenging. If you replace a 1.5 arm with a 1.6 arm everything that happens on the valve side of the arm occurs quicker, or sooner. According to Dick Jones, Jones Cam Design, when he tested a cam with 268* duration @ 0.050” lift, he found the cam picked up another 2* duration with the addition of the 1.6 arm. At 0.200” lift it saw a 4* duration increase. So, maybe increasing the length of time, along with the additional lift, will better evacuate the cylinder by the time it gets close to TDC. Might work
I like your attitude…do not remove the zoomies!
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If you decide to change the rocker ratio, your piston to valve clearance will be reduced, you will be closer to coil binding the valve springs and your retainer/lock to valve guide (or seal) clearance will be reduced. Make sure you check everything.