What should my MPG be?

[bobcowan]

Originally Posted by paulmartin

i get a lousy 6 -8 mpg , 347 stroker ,4x 50mm ida webers , 205 AFR heads , and i like to floor it.....TRYING TO FIND IMPROVEMENT

I hate to be the one to break it to you, but you have a mismatch of parts. You've lost all your efficiency, and a lot of your power.

With an IR intake system, it's pretty important to maintain proper sizing through the entire system. If you start with a certain sized port, and move the air into a larger area, the velocity will slow down, he fuel will come out of suspension, and you lose power and efficiency.

You throttle bodies are 50mm - slightly smaller if you calculate in the volume loss for the blades. But your intake valves are 52.83mm. Much too big. Especially with those gigantic ports. Your fuel is puddeling in the chamber above intake valve, and then dripping into the chamber. It doesn't ignite very well in that condition. And, because you've lost your intake flow velocity, you don't get very good chamber filling.

Swap those huge AFR heads for a pair of Dart Pro-1 195 heads, and I almost guarantee that you'll get more power, better throttle response, and better fuel mileage.

Now, you're probably reading this and thinking, "What a load of BS! That's all just theory." No, not really. take a look at this dyno sheet. The botom line is larger ports and valves, and the top line is small ports and valves. My throttle bodies are also 50mm, but I have 427 cubes to feed, and a huge cam.



Also, what cam are you using? If it's a standard SBF cam with 110* LSA, you should seriously consider changing it.

Once you have all the rights bits that go together, then you can work on getting a good tune.