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<blockquote data-quote="olympic" data-source="post: 16185555" data-attributes="member: 168598"><p>There's 2 main problems big cams cause due to their excessive valve overlap:</p><p></p><p>1) low manifold vacuum. This causes the blower bypass valve to either stay closed or act erratically at low RPM, causing the car to buck, jerk and surge during low speed driving. I have to slip my clutch like crazy when taking off from a stop because if I let the RPM's drop too far the car will stumble and buck, sometimes even stall or backfire. Basically any driving below 2000 RPM is pain in the ass. A low vacuum bypass actuator DOES NOT solve the issue. A twin screw blower needs a strong intake vacuum signal to function properly.</p><p></p><p>2) intake reversion. During valve overlap hot exhaust gasses get sucked back into the intake manifold causing high IAT2's and heat soak. I can't drive my car in city traffic for more than about 20-30 minutes on a hot day. IAT2's will hit 170F even though the Killer Chiller has the IC fluid at 40F and the engine will heat soak so bad that it doesn't want to run.</p><p></p><p>I love the sound of the cams and will miss it but I built this car to drive and enjoy and the Stage 4 cams just made me hate driving it. If you're dead set on cams get some custom grinds from someone like Todd Warren who can spec the cams for your particular build. A local tuning shop is also a must because tuning driveability issues over the internet is very difficult.</p></blockquote><p></p>
[QUOTE="olympic, post: 16185555, member: 168598"] There's 2 main problems big cams cause due to their excessive valve overlap: 1) low manifold vacuum. This causes the blower bypass valve to either stay closed or act erratically at low RPM, causing the car to buck, jerk and surge during low speed driving. I have to slip my clutch like crazy when taking off from a stop because if I let the RPM's drop too far the car will stumble and buck, sometimes even stall or backfire. Basically any driving below 2000 RPM is pain in the ass. A low vacuum bypass actuator DOES NOT solve the issue. A twin screw blower needs a strong intake vacuum signal to function properly. 2) intake reversion. During valve overlap hot exhaust gasses get sucked back into the intake manifold causing high IAT2's and heat soak. I can't drive my car in city traffic for more than about 20-30 minutes on a hot day. IAT2's will hit 170F even though the Killer Chiller has the IC fluid at 40F and the engine will heat soak so bad that it doesn't want to run. I love the sound of the cams and will miss it but I built this car to drive and enjoy and the Stage 4 cams just made me hate driving it. If you're dead set on cams get some custom grinds from someone like Todd Warren who can spec the cams for your particular build. A local tuning shop is also a must because tuning driveability issues over the internet is very difficult. [/QUOTE]
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