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i'VE BEEN PLAYING WITH THE ENGINE ANALYZER ON MY COMPUTER TRYING TO FIND THE BEST CAM FOR MY PURE STOCK CAR. I'M USING THE MOST RESTRICTED VARIABLES BECAUSE I MUST USE STOCK INTAKES,EXHAUST MANIFOLDS,2BL/ETC'ETC.WHAT I'M FINDING OUT IS THE WIDER THE LOBE SEPERATION THE MORE POWER IT IS MAKING. TYPLICY LOBE SEPERATIONS FOR RACING ARE 108 AND DOWN BUT THE COMPUTER IS SAYING LOBE SEPERATIONS IN THE 114 TO 116 RANGE MAKE THE BEST POWER IN THIS RESTICTED COMBINATION.ANY THOUGHTS ON THIS???
 

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Narrow lobe seperation angles are only beneficial with combinations that have the exhaust side of the engine optimized. With long tube headers of the correct diameter, if they are run open or with an extremely low restriction exhaust system, the high velocity exhaust gas is able to produce negative pressure in the exhaust port near the end of the exhaust stroke. When that is happening it's often beneficial to narrow the lobe seperation angles which in turn creates more overlap and allows the intake port to be exposed to this negative pressure for a longer period of time. This counteracts intake reversion and actually helps to get the intake charge moving in the right direction before the piston starts down the bore. However, if the exhaust system isn't optimized the negative pressure isn't there. Instead there is backpressure, which has the opposite effect and actually creates reversion in the intake tract. With that in mind it's not hard to see that under those circumstances that less overlap, which is created by widening the lobe seperation would be better. Widened lobe seperation cams also open the exhaust valve sooner, while there is a little more pressure in the cylinder which produces a more violent initial blowdown and helps exhaust flow, which of course would be beneficial in a restricted system. As well, most wide lobe seperation cams are usually run in an advanced position to get the intake centerline angle at approx 110 degree ATDC for best torque. This also opens the exhaust valve sooner which helps exhaust flow. When all of these things are considered it's not suprising that your engine with stock manifolds will respond well to a cam with wide lobe seperation angles.
 
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