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Old 08-25-2005, 10:06 PM
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power loss from higher ratio rocker?

Hey guys, im just curious about the theory on higher ratio rockers possibly killing power? I've heard so much about this and that, I'd like to get it straight. I hear of people running split duration 1.5/1.6 and ive heard of using the higher ratio on both exaust and intake. So what's the deal with that? What makes the difference of which side you would want to run the higher one on? Why would running higher ratio on both kill power?

I recently rebuild my engine and changed from 1.5 stamped to 1.6 roller tip rockers but haven't finished the engine yet so im curious what to expect. Isn't it in theory just like running a higher lift cam?
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Old 08-25-2005, 10:40 PM
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If the flow curve of the cylinder head compliments the additional lift you should make additional power. We use 1.6, 1.7 and 1.8 ratio small block rockers depending on the application and situation.

The situation on what to run depends on the flow of the head. If you have a VERY weak exhaust port you may want to run a higher ratio rocker on that side. For us to determine what we may do we flow the heads, port as needed, reflow, spec a cam, dyno the motor and test combinations.

In general on something like a stock head motor, with mild cam it can usually pick up some power with 1.6's on the intake and exhaust.
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Old 08-25-2005, 11:31 PM
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Cool that makes sense. It sounds like determining what ratio to run is really an in-depth process rather than just knowing to slap them on here or there. I recently did a medium duty port job my stock heads and also upped from a performer to a performer RPM manifold to pick up my top end and clean up where im supposed to be maxing power. I figured a set of 1.6 roller rockers would help comliment the extra head flow and taller intake manifold. Hopefully this is correct, i just got worried hearing about them killing power or having to run splits here or there without knowing.
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Old 08-26-2005, 12:11 AM
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Give it a try but make sure to verify clearance as you roll the motor over setting lash. It's also a good idea to check piston to valve clearance (P/V). If you have not decked the block though I would think your OK.
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Old 08-26-2005, 02:45 AM
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Rick,
I bought new valve springs specifically for the new calculated lift (adv cam lift / 1.5 x 1.6 = ) so that should be covered ok although I will check with a feeler guage (what is it, .030 gap per coil?). I'm learing all kind of crap about head and valvetrain stuff. I just got done correcting the intalled height which was lucky I checked because some were off by .090+ and if I never asked I wouldn't have even known to check it in the first place.

It may be hard for me to tell whether the extra ratio helped or not since i did all that other stuff as well. I guess if I'm up to the task I could switch back to my stamped 1.5's to see but I don't know if my butt dyno would pick it up (or maybe a run at the track?) Then again it's roller vs/ stamped, my experiments won't really hold a solid control variable no matter what I do. I just figured the extra lift is just like running a bigger cam and I couldn't think of any power hindering in that.

Anyways, thanks for your help, really appreciate it.
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Old 08-26-2005, 08:20 AM
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.050 to .060 with your feeler gauge. Also note the clearance on the pushrods and rocker to retainer clearance. Make sure noting rubs or makes contact with anything.
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