jeffswav

I agree with Jason & Eddie, I love MPI, carbs are old school. Most of the guys here like them because they are bolt on and mechanical adjustment.
Eddie is a expert with the factory merc equipment. But the average guy can get a aftermarket system and tune with a laptop like I do. Its not rocket science, its just a computer.

sickoutlaw

My original post was because I have a stock 502 mpi and planning a 565 rotating assembly.... What would have to be changed to keep efi. I understand the advantages of efi but correct me if i'm wrong.... to properly tune the a dyno is required and a programmer. What else would be required?? Thanks

jeffswav

Eddie can help you with that, I have seen him use the Holley manifold and the Merc computer. I have seen the stock MPI setup work on 540's.

JasonSmith

The flat top manifold you have now isn't the best choice for your future application. Eddie will agree. Jeff is right on for the swap. At that point you'll spend more $$ on keeping the EFI than you will going carb. You're going to have at least $800 worth of injectors to buy, a throttle body & new intake manifold, air cleaner/flame arrestor throttle linkage......
Something like this is what you'll end up with. Not this system, but some of these components.
I know it can be pieced together and your ECM and wiring harness will work, I'm just giving you a "for instance".

ThisIsLivin

No one has brought up the subject that carbs make more HP due to the cooling effect of the fuel. Just check Engine Masters, they have to give fuel injection an advantage to make them competitive. Having said that, if I didn't need to buy headers to put EFI in my boat, I would go with EFI. EFI motors run so much smoother. I've converted a carb motor to EFI in a car. It ran so much better my wife even noticed, not to mention better fuel economy. Changing fuel ratios with a keyboard is a lot easier on the water than swapping jets any day. It also doubles as a great security device. I kept a non-running profile saved so when I had to park my car in a bad area, I just loaded the non-running profile.

Young Performance

Outlaw,
As far as I'm concerned, you need to dyno the engine either way you go. I wouldn't build a totally new combo and not tune it on the dyno. Not only that, you get to break it in under controlled circumstances with unlimited monitoring equipment, check for leaks, find peak power and torque, etc. Without it, you are guessing as to where to prop it, where to cruise, etc.
I didn't know you wanted to add so many inches. Still, it depends on how much power you are looking for. The manifold you have is only good to about 600 hp. After that, forget it. I use a really nice setup from Holley. For about $2600, you get the manifold, 2000 cfm throttle body, fuel rails, injectors, tps sensor, ect sensor, map sensor, iat sensor, hardware, etc. You can use your existing harness with some mods. You can also use your existing ecm.
You can offset some of the cost by selling your current intake. A good intake and carb setup will cost about $1500, so the efi setup is a little more. IMO, it's worth it.
Give me a shout it I can help.
Eddie