head porting and fuel consumption???

[Glamis400ex]

Hi gang,

I heard/read somewhere that head porting affects the fuel mileage. I read on another site where a guy had a 370cc Banshee with head porting and it sucked so much fuel, he couldn't hardly ride it in the dunes for more than 2 hours, without turning back to camp to re-fuel.

If it does comsume more fuel, please explain how.

Just curious what you all say on this. I am building a 416 and know exactly how far I can go on a stock machine. With the 416 and porting, I'm gonna be seriously bummed if I lose more than 15% fuel economy.

Thanks,

Glamis

[Pappy]

hammerdown = spent fuel

i dont see how porting alone could decrease fuel consumption.....but a 370cc shee in the sand....id have the hammer buried so id expect it to suck fuel like a big dog

[Glamis400ex]

Thanks Pappy,

Yeah, I really don't either, since it's the exhaust that gets recieves the port work...I dunno, just something I heard/read...:ermm:

Glamis
i dont see how porting alone could decrease fuel consumption.....but a 370cc shee in the sand....id have the hammer buried so id expect it to suck fuel like a big dog

[Pappy]

when i had my heads ported in my street car i actually gained fuel milage. i reckon the engine was more efficiant...ofcourse with power on tap id usually blow what id have saved more times then not:p

compression will affect it....and id imagine a poorly jetted carb would hurt and or help too

[SGA]

I agree with Pappy. I bet he was laying it down in the dunes with that banshee. I would be.:D Porting should not effect mileage very much, even going up 20- 50 cc's should not make a big difference in gas mileage. I would imagine with the new found power, you would be nailing it alot more, which would cause the MPG to drop.

[SGA]

Just thought of this. Dont make the mistake of thinking you need a big ole main jet because of mods. Check with some others with 416's on the site, and see what works for them. Go by the plug color, it should be dry, and a light tan color.

I cant tell you which of the mods caused the increase in fuel consumption but it goes thru a lot more now than b4.

Would have to think that a higher flowing head would require more fuel to make use of the extra air avail to it and that would have a lot to do with it. I know that the typical ported, polished, cammed and larger bore motor is going to be wanting larger jets so I guess that means more fuel used.

Sort of makes sense now that I think of it :D