Hey guys thanks for the responses! First, we ran all of our dyno tests on 89 octane shell pump gas. We showed absolutly no knock events on the Mercury computer which has max advance at 28 degrees. On the earlier tests on the MEFI computer we ran the timing from 27 to 36 degrees and also had no knock events. This combination seems to like the 28 to 30 degree timing advance best and makes the most power there. Our quickburn chamber in an aluminum head is the reason. The big overhanging combustion chamber on the stock iron heads is the problem for this motor, it knocks with any timing above 29 degrees. The horsepower and torque figures given on this run were with a set of e-top headers and on the earlier run with the standard merc 496 exhaust manifolds we made 518HP so the stock manifolds are not to bad and torque was only slightly lower. This run produced 533HP at 5100 rpms with 610 ft. lbs torque at 4300 rpms. The exciting news is that the torque was over 525ft.lbs at 2500 rpm and remained over 525ft.lbs all the way to the 5100 rpm redline. Kind of like a diesel torque band> Heck, better than a duramax diesel with a chip! Its the high torque at both low and high rpms that's going to be the real thing you expeirence in both acceleration and pulling more prop for higher speed. What would you rather do, buy a three year extended warranty or have other 496 powered boats throwing prop wash over the front of your shiney new boat -DA! Have fun and be safe in your waterrods. We are here when you want more power!
Ray @ Raylar