2 jeted and gas miles

[kris's66lwb]

any one know where i can get a rebuilt rochester 2 jet or is a 2 jet the same as a 2g. does anyone knoiw how to get better gass millage i replaced the cap plug wires and plugs i still need to do the rotor and coil i need a fuel filter and a new carb gonna stick with the 2bbl what else can i do 8 miles to the gallon is starting to hurt

[wild one]

What type/size engine are we talking about? A V8 I assume?

[kris's66lwb]

v8 327

[Tim64]

You would get better mileage out of a 4bbl. If you get the right one, the primary bbls will be much smaller than the 2bbl, and as long as you keep you foot out of the secondarys you should get much better mileage. I've had several V8's that got 20mpg.
Tim

[kris's66lwb]

what else should i do

[wild one]

As Tim stated, a swap to a four barrel carb usually increases fuel mileage, I say usually since the key to achieving the best fuel economy is directly related to how the truck is driven.

For example - in my application (Stock 1975 400 CID SBC) I run a four barrel intake with a four barrel carb (Stock cast iron intake with a Quadrajet), an HEI distributor, shorty headers with a really crappy/old 2 inch dual exhaust, 3.73 gears in the rear with a 26 inch tall tires. At 65 MPH with the engine spinning approx 3000 RPM I get 13MPG.

I will be changing the gear ratio to 3.40's soon, replacing the intake with an Edelbrock performer, R/R the entire exhaust system and use full length headers with a larger diameter pipe, and swap out the cam to an " RV " type grind. With these mods performed I will spin approx 300 less RPM at cruise, Increase the efficiency of the engine which should increase my mileage and as an added bonus will increase my engines overall H.P. output.

[kris's66lwb]

k so cam carb in take and exhaust and gears whit the gears the lower # is faster or slower

[kris's66lwb]

all right i have an edilbrock alum intake man and a holly 4bbl or i could get my hads on a roch. qjet for practily free which one is better for reliabillty and gas miles

[wild one]

1st question : As far as rear gearing goes, the lower the number ( 2.73, 3.07, 3.40 etc..) the less rpm the engine will spin at any given speed where as the higher the number ( 3.73, 4.10, 4.56 etc.. ) the more rpm your engine will spin.

The trade off between the two is overall acceleration of your truck - the higher number gear makes the truck " feel " faster from an acceleration stand point ( the engine revs quicker due to a better mechanical advantage ), but you sacrifice fuel economy at higher speeds ( 55+MPH ) due to your engine spinning at a higher RPM.

Another factor in overall cruise RPM is tire size. A taller tire travels a greater distance per revolution allowing your engine to run at a lower RPM. Example : A truck equipped with a 3.73 rear gear ratio and 26 inch tall tires ( 275/50-R15's ) will spin approx 3200RPM at 65 MPH, the same truck with 28 inch tall tires ( 275/60-R15's ) will spin approx 3000 RPM - thats a difference of -200 RPM with nothing more than a simple tire change.

Here's a couple of websites I used to calculate the tire sizes/RPM's http://www.therangerstation.com/tech...nch_Tires.html
and http://www.csgnetwork.com/multirpmcalc.html

2nd Question : Depending on what style of a holley you have ( vacuum secondary or mechanical secondary and what the carbs cfm rating is ),would determine if that particular carb is best suited to your needs. The quadrajet carb if it the right size/style and in good working order would probably net you the best overall fuel economy. The primary's are tiny compared to the secondaries, and most if not all of your cruising ( part throttle ) would be done with the secondaries shut.

Sorry for the length of the post, just trying to cover as many variables as possible.

Pete

[kris's66lwb]

thanks pete my truck has 35s and the gears im gesuing are low it reves real high and about 55mph that 5 mph under the speed limt on most the roads i take but as im told there are no new gears for my rear end that i can get i think called it an eaton it has a perfictly round diff cover i seel them a lot in the c20s which i have a k20 and have never seen a noter one in thje k20s there alway dana60s i would go to a dana 60 i found one from a 1966 chevy k20 for 350 but at my schools auto shop we dont rebuild axels so it would cost and ass load to get my d44 and a d60 up graded to some thing that will get me moving faster i dont know what holly it is but is vaccum secionarys and electric choke it needs to be rebuilt and so does the q jet but i can rebuild a q jet or a holly or both

[Fred T]

For general driving the qjet will get far better milage than the square-bore. Biggest problem with them is throttle shaft wear. If I remember right, .007 play fore & aft means the shaft needs bushings.

That said, the big issue is the gearing. Carb & ignition will help some, but getting the revs down to 2,000 at highway speed is the way to get better milage.

I know how tough it is to get under 4.10 gears on a 3/4 ton 10 bolt. Have you looked at the 14 bolt?

[kris's66lwb]

thought about it but but to may mods to the tubes get them to fit 6the period correct d60 i could get under the 410 what would be the best gera 373 or what