so... i used to get 30 mpg on the highway in my 92 spfi 2wd wagon, on a good day. now i have a hatch with a spfi long block and a hitachi carb. my secondaries are not opening, so i got no power. but... i am getting close to 40 mpg! if you need some insane gas mileage action. plug the vac line going to your secondary. does wonders in these tough economic times.

That's a great idea! I think I'll be going out and trying that this afternoon. I only use my car for commuting to work - as long as I can get up to highway speed, it doesn't really matter how long it takes, and the less fuel I use, the better.

Hmmm.

Maybe a vacuum switch on the dash?

Hmmm.

my old honda accord saves fuel with an extremely stiff gas pedal spring. it requires force to get anywhere near the floor, and going up mountains gets your foot tired, but boy does it save!

Just another possibility, your increase in mpg may be due to the fuel level in the float bowl being lower than specified. Thus, the main jet circuit has less fuel (level in the bowl) to draw from.

 

Back in early 80s, I put a device I made on the carb of my 72 Charger w/318 V8. The idea was, that I used a certain amount of manifold vacuum to apply a slight vacuum (lower atmospheric pressue) in the float bowl. By doing this, at cruise and normal manifold vacuum, the carb was not able to pull as much gas from the bowl and out the main jets. When one tromped on the pedal, the manufold vacuum drops, thus, the mains could pull the gas from the float as normal. Esentially, leaned the engine a bit, once up to speed and normal manifold vacuum was restored. I was getting somewhere in the mid 20s for mpg. Depending on how much I wanted to lean the engine at cruise. Acceleration was normal.

 

Boy, I miss the carbed engines. Why were they taken away from us?

with a good efi system you could be getting better than 20mpg on a 318. Thats why fuel injection took over. It also helps engines last longer because the a/f is kept nearer perfect, making engines last longer due to less carbon production. Generally on a carb motor the oil begins to become black from carbon between oil changes if the carb isn't tuned exactly right. All of the efi motors I have seen have kept the oil amber. This has just been my experience, and its a pretty far fetch from a controlled experiment, but there ya go anyways.

No more carbs for me. Rebuilding them...tweaking with them...buying new ones or parts for them. FI is the way to go.

holy back from the dead......

cheers, brian