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Horsepower figures for a 331
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[QUOTE]Originally posted by AaronC: [QB] [qb][/QUOTE]I'm following you guys here ... but does this imply that the less duration and lift on the exhaust is better for smog???? Overlap is the amount of time the intake and exhaust valves are open at the same time. The more overlap you have the worse the emmisions will be. Seriously, a custom cam done by a reputable efi mustang guy can provide great gains. The new technology of fast ramp rate lobes has allowed for better drivability because the valves open and close much quicker, keeping velocity high and giving the cylinder more time to compress it's air/fuel charge. The guy who did our cams likes to have the cam degreed to have a later intake closing point because of the "ram" effect the long runners provide. For ex. most cam companies have advance built into their cams. The X cam for instance if installed 'dot to dot' should come out to a 107-108 intake centerline. A cam is said to be installed straight up when it's installed on the same intake centerline as the Lobe separation. So the X cam has a 112 LSA so the real straight up would be 112 intake centerline when degreed. My cam has a 111 LSA and is installed at a 113 intake centerline, therefore 2 degrees retarded. Now if you look at the closing points for the X installed dot to dot (107) and mine (113), you can see that's a 6 degree difference as to where the intake valve closes. Mine was set to that because of my Performer intake that measures around 20" long. Basically he's saying you won't give up torque when the cam has a later closing point (when degreed for your application), but will gain top end power because the velocity through the runners is still high and if you close it too soon you're basically slamming the door on a still high flowing intake charge. I know it's a lot of crap I just threw out, but it makes total sense and his work has proven to be very successful. The great thing I liked about him was that even if I had chosen an off the shelf cam he still told me where I should degree it for that cams optimum performance, and in some cases stick 1.7 rockers on the intake side only. The main reason he keeps the exhaust side calmer is because overlap doesn't work (scavenging) if exhaust velocity isn't high enough to pull the intake charge through. He can explain all this much better than I can. His website is [URL=http://www.hitechmotorsport.com]www.hitechmotorsport.com[/URL] if you want to check it out. If you have any tech questions call him or E mail him. He's been most supportive with me and Mike to make sure we optimize our setups. [/QB][/QUOTE]
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