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hyd roller cam vs hyd. flat tappet cam

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Old 12-18-2010, 07:20 PM
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Default hyd roller cam vs hyd. flat tappet cam

I was wondering if someone could tell me the difference between the two and what would be the loss or gain of hp between the two? thanks

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Old 12-18-2010, 08:43 PM
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The roller actually has a roller on the end of the lifter that follows the lobe of the cam shaft where the flat tappet's flat bottom does same. W/a roller you are able to get much more aggressive with the lobe profile (lift + duration) than you can on a standard hydraulic w/o issues. Much less friction as well.
To me it's win win but..........., in a mild motor you'd probably see nothing and they are way more expensive and more parts to break and go through the motor. ON a modded motor though they're all but mandatory plus a lot of OEM motors are now roller motors from the factory.
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Old 12-18-2010, 09:28 PM
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Here are a few of the differences that effect performance.
Flat Tappet: Advantage - the complete system is less expensive. Disadvantage - Spring pressure is limited both on the seat and on the nose of the cam, thus valve stability is not great, WOT rpm limited. Lift is limited to about .575 due to side loading of the lifter, increased duration is also difficult due to side loads. Most oils produced today have the zinc additives removed, this is critical to wear resistance in a flat tappet application. Hydraulic Roller: First there are two systems, the GM factory lifters that utilize rotation limiting assemblies and and a retainer octopus style plate bolted to the block. This system is limited to about .610 lift but has all other advantages of the roller set-up. Second there is a tie-bar lifter system, sometimes called the retro-fit lifters. These are not lift limited for most applications. All hydraulic rollers can have more seat and nose spring pressure, therefore better valve stability. There is a roller wheel contacting the cam, less friction. This wheel reduces side load effects so more aggressive lift and closing ramps can be used. This opens and closes the valve faster leaving it open longer and bigger, better flow. More duration can be used due to lack of side loads. Disadvantage is the cost and the camshaft must be accurately located in the block. Conversions to roller require different pushrod lengths than flat tappet. Finally, and this is only my rule of thumb but you can reduce the duration of a roller cam by about six degrees and acheive the same power as a flat tappet cam engine. Example a 236/242 duration @ .050 flat tappet, would be a 230/236 @ .050 roller. The reduced duration increases the cylinder pressure, thus the torque is better and the idle smoother. Good luck with your decision.
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Old 12-18-2010, 09:48 PM
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castrol gtx full sytnthedic oil has a grade special made with zinc for flat tappet cam
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Old 12-18-2010, 10:22 PM
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Valvoline Racing VR-1, Joe Gibbs, Brad Penn, most full synthetics and others have it. The zinc has been removed from most conventional oils, my point is you have to look for it and it is a major issue needed with flat tappet applications. Alot of the flat tappet cam lobe failures are attributed to the oil. The quality of the heat treating of the camshaft core is also a major factor in the life of the cam lobes.
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Old 12-19-2010, 05:28 AM
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thanks for all the info that cleared a few thing s up
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Old 12-19-2010, 06:30 AM
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Default Interestin theory.

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Originally Posted by Boat1 View Post
Finally, and this is only my rule of thumb but you can reduce the duration of a roller cam by about six degrees and acheive the same power as a flat tappet cam engine. Example a 236/242 duration @ .050 flat tappet, would be a 230/236 @ .050 roller. The reduced duration increases the cylinder pressure, thus the torque is better and the idle smoother. Good luck with your decision.
Makes sense and I can see it as a big advantage especially in a boat trying to idle around a dock w/big wheels and a steep cam.
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Old 12-19-2010, 07:55 AM
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go roller or dont go
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