My daily driver is an 86 Z-28 Camaro with a 305 and 700r4 trans, 2:73 gears in the rear. The motor has over 130,000 miles on it. I have a rebuilt 305 motor waiting to go in. That engine has a 79 shortblock with 91 tbi heads on top, edelbrock performer cam also. I will be putting the edelbrock performer intake off the motor in the car as well as the 600 edelbrock carb on that engine before dropping it in. The car has headers going into a 3" exhaust back to a flowmaster style muffler and dual 2 1/2" tailpipes. I currently am getting 13-14mpg. I am hoping to see a bigger improvement when the engine swap is done. I have a friend with a 3:23 posi rearend I can get too. Any suggestions? I can't get another car i.e. gas economy car because the budget won't afford it. Besides I'm not a fan of front wheel drive cars and all the maintenance headaches that can come from them. (trans issues, wheel bearings, etc.)  

I'm unsure of the E-Brock Performer cam specs off of the top of my head, but for the sake of your mileage I hope it is ground a wide lobe separation angle and has duration and lift numbers that aren't much more significant than stock. Roller cams show significant mileage improvements because not only do they reduce valvetrain friction (this is very slight) but they substantially reduce valve overlap area, which makes the camshaft seem smaller than a flat tappet camshaft of near the same seat duration.

Headers and a manifold change should help mileage but remember to keep the exhaust heat crossover open. Don't go with lower gears. Even though they are just slightly lower theres no reason in raising the cruise rpm of the engine even if you're unsure of it will effect mileage by a measurable amount.

Hopefully this engine has a good static compression ratio for 87 octane fuel. Using the most compression possible improves combustion turbulence (burn rate), increases thermal efficiency, and increases exhaust velocity (just to name a few), all of which are conducive to improving fuel economy...  

Your performer cam duration is 204int. and 214ex.w/112 lobe sep.A little big for a 305 when mileage is important Crane has a 184int. and 214ex. this will build good low rpm cylinder pressure like Guru stated. Also I agree keep the 2:73's. Don't forget to check tire pressure once a week. Also a 500 cfm Edelbrock would help some. WIEDER  

I've got a '92 305 Camaro, stock form the car gets about 25 MPg on the highway, and mid teens in the city.

The post above is right, you want a cam that's gonna make a lot of vacuum and bottom end torque (what the 305 was designed for) if you get both of those, you'll get good mileage from your car.  

One of the many ways to improve your mileage would be to get an Edelbrock Rod & Jet set for calibrating yor Edelbrock Performer Carb. An ecellent choice of carburetor. I currently have a 267 in a 1980 Malibu with that same carb and matching intake. I also used Flowtech Afterburner Headers, which are designed with 1 and 5/8 ports to improve low RPM torque, and my exhaust is 2" duals with turbo mufflers. I can avg almost 29 mpg qith a THM 350 and 3.08 gears on the highway. I get aroud 17-19 in the city. I have also set my carb fairly lean since it is a rather large carb for a small engine. My initial timing is set to 10 degrees BTDC. If you have the calibration manual it helps with selecting the jet sizes, metering rods, step-up springs, and pump position with your particular set-up. Also if you change to a 3.23 it might take a mile or two off your highway MPG, but will add to your city slightly, as the car will not take as long to accelerate with the same amount of throttle. Your rear axle does nothing more that multiply the torque going to your real tires. In short you'll need less throttle to travel at cruising speeds.  

I would like to keep the current cam in the rebuilt 305 (money or lack there of). I drive 8 miles one way to work and the speed limit averages 35-45. The car with the OD engaged runs around 1500 rpms at that speed. So I was thinking that 3:23 might get the engine up where the power comes in. As a side note I drove the car on the highway to pick up a cowl hood this last summer and with no hood on I got 19+ mpg. First time it's ever done that. Oh I'm running 16" IROC rims and 50 series tires too.  

Wait are you using 205-50s. Your mileage may be off, cuz speedo may be off from the tires and rims not being stock. You can go to www.700r4.com to use their speedo calculator, RPM calculator, etc and find out if there is a discrepency. Also if you are at 1500 RPM, chances are your lock-up converter isn't engaged. This means your engine is losing more power/torque from converter slippage. Try driving in "Drive" and your RPM will kickup to about 1700-1900, but you'll have 1:1 ratio to your rear-end. Here's the breakdown. If your engine at part throttle makes 85 ft-lbs. at 1500 RPM, and you are in "OD" that 85 X 0.83 X 2.73(axle ratio)= the true torque generated at that RPM and throttle. I pulled these number as an example. You will lose approximately 25% of your torque and HP through your drivetrain. That doesn't count what you lose from converter slippage. Also you can try to get an aluminum driveshaft to replace your stock steel one. It is lighter weight and will improve throttle response by lessening the power loss through your drivetrain. Tire size will affect MPG also. A wider tire has more surface touching the road, this improves tracion and performance, also it increases friction. Friction from the tires will rob you of MPG. A thinner tire will hamper your cornering, but will lessen the resistence of keeping the car in motion.  

I know the OD is locking up because I had to install an aftermarket kit for it. I will check and see if the speedo is off. Thanks.  

djtricia:
I know the OD is locking up because I had to install an aftermarket kit for it. I will check and see if the speedo is off. Thanks.

You can try to drive on an interstate freeway. Drive past 10 mile markers and watch how many miles count on your odometer. Every 10 miles I drive my Malibu only counts 9.3 miles. This shows a 7% discrepency. No shops in my area calibrate speedometers though, so I have a formula that helps. My odometer show 93% of actual miles driven. So you take miles driven on trip, if you have one, or odometer. Let's say you drove 350 miles on your odometer with my 7% discrepency. You take 350 and divide it by 0.93 which would give you the true miles driven. Then take that figure and divide by total fuel used to refill the ENTIRE tank of gas. In my Malibu a full tank is 23 gallons, which runs me a meager $92 a fill up. In short 350/0.93= 376.34/23= 16.36 MPG. Hope this helps if you have discrepencies. I am also gonna put a 700r4 in my Malibu, but I am gonna use a 3.42 axle. Should give me about 1900 rpm at 60 MPH. Right where my engine should build decent torque, without consuming gobs of fuel from lugging the engine.