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Old 07-31-2007, 04:47 PM
oldbogie oldbogie is online now
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Quote:
Originally Posted by Jared
Would I be better off running full roller 1.50 ratio rockers such as summit's SUM-G6910B or roller tiped steel rockers like comp cams 1.52 ratio magnum steel rocker. both are about the same price. The reason I ask is I have heard the full roller rockers become loose at the pivot point over time and fail or become sloppy. if you need my engine specs look to my dyno software question on page one.
Some insight as what the engine is, cam, compression and how you're using it would be quite useful.

Generally putting roller rockers in the same ratio as the OEM factory used and running on the street doesn't buy much. With an OEM cam or up to about 225 degrees duration when measured from .050, going to a 1.6 where 1.5 was original is good for 10-15 hp at red line with a 2-5 pound loss of torque below 3500 revs.

On a competition engine roller rockers effectively reduce ball fulcrum friction which allows RPMs you otherwise can't get at with any reliability. This also reduces temperatures generated in the ball fulcrum which the oil has to take away thus eventually taking some load off the cooling system as well as adding life to the oil by not coking and otherwise frying the stuff. On the valve stem end of the world, the rolling moment reduces the side pull that a sliding rocker imposes on the stem. This again is a friction/heat reducer but also takes some side loading off the stem and guide which results in maintaining better dimensions between the two which improves heat transfer from the valve thru the guide into the cooling system making for happier (especially exhaust) valves. One has to realize that a competition engine being raced has some REALLY big friction and heat issues that are totally unlike anything seen on the street and these issues demand different engineering solutions.

The move from 1.5 to 1.52 is strictly an attempt by competitive racers to squeeze every bit of power out that the rules will allow, again all this is in the upper RPM ranges with long duration very high lift cams which work the valve train extremely hard. For a street engine the difference between 1.5 and 1.52 rockers would go un-noticed.

This is not to say you shouldn't run roller rockers on the street, but dyno and timing slip results vary widely between something and nothing being there.

It's a mighty good idea to run magnets in the heads oil returns and screens over all the valley to crankcase holes because if a roller fails, spilling its guts into the engine, it gets mighty messy when those chunks of roller bearing get into the oil pump and shot around the crankcase with the windage.

Bogie
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