Hi Smitty:

If I remember correctly the original size of the hole was about 1/8" and we opened it up to 13/64", which gives about 2.5 times the area. This has to have some effect on flow. Are you going to install the 50 lb/hr injectors? Since #5 cylinder was OK I guess you don't have head gasket problems. You're smart to check now.

When you install the AFR heads I hope you can check your pressures throughout the system again. It will be a great example of what happens when you reduce restriction in the heads.

Thanks Tom,I'm either going to put bigger injectors in mpi set-up or a different fuel injection system(a open plenum intake with a 2000cfm throttle body on it and machined for injectors w/fuel rails). AZSM says i need 65 lb injectors,seems like a big jump , although you don't run as much fuel pressure. With the right size injectors in a mpi setup does anyone out there think there is alot to gain with a aftermarket intake using fuel injection? This is a supercharged 540 running 8-10 psi boost blowing thru manifold. I am going to build a better adapter to the merc mpi than procharger gives you if i stick with factory manifold,thanks for anyones resposne,Smitty

Tom,I will also check blower pressure drop again from point a to b,i'm sure it will be greater if heads aren't backing pressure up into intake manifold,Smitty

Smitty: If you go with Jim's recommendation on the single plane style intake then it really makes sense to switch to the carb style supercooler box, if you have the room. Your current intake is 11" above the block. A Holley single plane EFI intake with any box on it will be close to 15".

We have a bottom plate cut to dominator pattern which is what the 2000 CFM throttle body needs. IMHO you don't really need anymore than the 1000 CFM but Turbojack has made the 2000 CFM work as well. We use the Holley single plane since it's fuel rails fit under our box.

You do need the 65 lb/hr injectors. As far as the difference between the intake manifolds, the single plane has shorter and less restrictive runners. It will make more power up top. You have the cubes and the boost to take care of the bottom end and if you want your drive to live it doesn't hurt that the single plane has less bottom end torque.

But...I've been looking into this a lot lately as we design a supercooler for the HP500EFI. I think that with a stock 502 aiming for 800 HP on relatively low boost and moderate RPM, the long runners are a definite advantage. They pump up the bottom end and don't begin to hurt until higher RPM where we're not going anyway. This is especially important if the boat is capable of 100+ mph and has to handle a big pitch prop when getting on plane.

Tom

I have the intake manifold and 1000cfm throttle body you need.

How much for the efi setup and whats included? Greg

Look in the parts swap forum.