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Old 10-19-2000, 05:49 PM
HankL HankL is offline
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I am interested in trying out a lower rocker arm ratio on the exhaust side of my 1995 Magnum style cylinder heads.

Does anyone know if AMC or other make rocker arms can be made to work on the Magnum cyl head stud mountings ?

I am looking for a ratio in the 1.4 to 1.5 range.

As a different way to go - does anyone make custom Magnum rockers with buyer-specified ratios ? I don't really need roller tips but would consider them.

( I am not after a hp increase. I want to test what opening the exhaust valve later does to low rpm/part throttle fuel economy.)
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Old 10-20-2000, 12:08 AM
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rumblefish360 rumblefish360 is offline
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A custom raito to order. WOW that would be great. The price would kill. There enuff money allready.
How about just trying an adjustable arm. Adjust it with more clearance for simalar effect. MAny conpanys make them.
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Old 10-21-2000, 03:58 AM
340king 340king is offline
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Changing the ratio of the rockers will have only a marginal effect on valve timing. It will slightly change the valve timing with respect to when it reaches .050" of lift. The change will be pretty small and probably won't be measurable on anything other than a very accurate dyno. The loss of lift may/should have a greater net effect on full throttle performance.

Opening the exhaust later is the same as widening the lobe seperation. This typically changes the overlap, pulse tuning, RPM when peak Volumetric Efficiency is achieved and other related items. For every action there is a related reaction (one of Newton's Laws), however, in engines they may not seem directly related. What you are attempting to do is maximize efficiency or produce the most favorable Brake Specific Fuel Consumption (BSFC) at low RPM. Typically the cost is full throttle/high RPM performance.
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