What should my MPG be?

[Roger Bray]

good news.
Checked the spark and it was good.
Then the engine started.
It still runs rought until it warms up. Maybe this is normal. I'll be doing some more research on the holley site.

[WardL]

I say check your tire pressure! Just kidding..... I get 12 and think gas is a bargain. Try driving around in your Cobra without it..... Besides how you drive, cubes, cam and carb set up will make all the difference in your gas mileage.

[Silversmith]

Vacuum??? What vacuum? I don't need no skinkin vacuum All mechanical! Distributor: mechanical advance. Carburetor: mechanical secondaries. Just mash & GO! I beleive in "KISS"= keep it simple stupid

[IndyCobra]

Originally Posted by Roger Bray

good news.
Checked the spark and it was good.
Then the engine started.
It still runs rought until it warms up. Maybe this is normal. I'll be doing some more research on the holley site.

Every time mine won't start it's because the float bowl in the Holley is dry. Shoot a little fuel in the vent tube and it fires right up.

I get about the same mileage as you. I've been busy working out a few kinks to worry about it right now, still trying to get that damn Holley to work just right. I'm about to switch to an Edelbrock. So far I've followed the Holley setup sheets to get things sorted out. Runs decent but not perfect.

[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

[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.