toxikdump

I would like to thank everyone for the advice... I guess Im going to go with the performer rpm air gap, and a 750 carb. There are only a few minor details I am not shure about. With the carb, should I get a real holley 'double pumper' or a regular 750 w/ dual feed. The double pumper has 2 accelerator pumps and costs alot more $$$ than a regular one. The regular holley cost about $250 and the DP holley is around $400. Also should I use an open spacer or the 4 hole w/ this setup. I would like to make most of the power beween 4-5k rpm. Thanks again !!!!!!!!!! I'll get this formula to run 65 yet!

robyw1

Please don't be offended by this but you couldn't be more wrong. The reason why a carburetor can't compete with port fuel injection is because of the reason you said it was better. The further the air/fuel mixture has to travel the worse the atomization will be by the time it's gets to the combustion chamber. There is no way a carburetor can atomize fuel as fine and consistent as an injector. Not only that; the injector (port) atomizes the fuel right at the intake port of the head. It doesn’t have to change directions and be pulled apart by other cylinders drawing fuel. Ever wonder why you always have some cylinders that tend to run leaner than the others? It is all because of the carburetors inability to properly atomize distribute fuel in an even pattern throughout the RPM range. With a port injection system you can have limitless dry intake shapes finely tuned to specific engine characteristics without have to consider wet flow. It makes a tremendous difference and significantly widens your options when building an engine for all out horsepower, efficiently, and reliability. EFI is so much greater that you can’t honestly compare it to carburetors. It is like comparing a Sony plasma screen to an old Curtis Mathis TV. Again I mean no disrespect to anyone. Once you take the plunge and starting building good EFI systems you will never go back.

Roby

RumRunner

Roby,

I take no offense to your comments. Not sure if you’ve actually ever tested this or not, but you’re not looking at right. It is simple physics. If you look at a high-end race engine the injector is mounted, as far away from the combustion chamber as possible so there is more time for the air, and fuel to atomize properly. An F-1 engine will have the injectors mounted in the air breather assemblies about 42 or 44 cm (18”) away from the chamber. It’s not practical to do this on most applications. It is true on carbureted engines you will have rich/lean cylinders, but still on the average engine due to better designed intakes available a carbureted engine will make more power than the injection. Injecting the fuel through the booster/venturi combination of a carburetor (using electronics to monitor, and maintain your fuel curve) will make more HP than direct port injection. I’ve done the testing on this.

Since we’re dealing with marine engines here, talk to the majority of engine builders, and you’re not going to find any HP gain on a marine engine going fuel injected vs. carbureted. Especially when you take the difference in price into consideration.