This winter i have been freshening/upgrading my 540/procharger motor and have debated pros and cons of modifying my stock 502 efi intake, plenum and throttlebody that i am blowing thru w/blower or just buying a good aftermarket intake and billet throttle body. When i built 540 2 years ago it dynoed kinda weak because of various reasons(too small of injectors,merlin heads w/only 65 % intake to exhaust ratio,8 rib drive that slipped on dyno slightly etc). The 540 only made 629hp and 697 ft lbs of torque. The boat went SLOWER (76 on gps) than it did w/502 w/stock cam and merlin heads. I was able to get boat to run 85 on gps by raising base timing,turning up fuel pressure,changed to 12 rib drive etc. The general consensous on this board was the 540 was making between 725-750hp at the edge of melt down. This thread is going to detail how i modified the stock intake and fuel rails without spending a ton of money just alot of sweat equity. I chose to modify the stock intake because i am over budget on my cylinder heads,cam,new pistons,thermal coatings etc. If the motor doesnt make at least 825 hp on the dyno the intake will go in the trash and i will just buy a good intake,billet throttle body and new plumbing to get boost to the manifold. Hopefully this thread will help a few of you guys(like sutphen 30) who are trying to do the same thing.
To start with i took the stock throttle body to our local head porter/flow guy and had it flowed with and without the screen procharger has you put in it when you convert your system. The throttle body w/screen only flowed 520 cfm at 28" water column,w/out screen it flowed just over 600. Although those numbers seem really low it is deceiving because throttle bodys are not rated by flowing them like we did AND a blown motor will push air thru it at a much higher rate.