Performance and Gas Milage

[redracergt]

I have '71 318 and want to know what would be the best carb, intake, cam combo, to get good performance but as well get good gas milage seeing as it will be a daily driver? 

[Tropicalcats]

Good performance and good gas milage??

[redracergt]

Ok, well good performance but that will not sacrafice gas milage too bad.

[Grancoupe]

You should try an old quadra jet carb. They had a really small set of primaries and a huge set of secondaries. Of course it won't fit on a holley square flange manifold. You'll need a manifold that can fit it or a spacer that will convert it.

With a set of dead gears (278's) my friend and I were able to get 28 mpg on the city/highway in a worked 67 Firebird with 400 block. We were driving out to Carlisle one year.

[GoodysGotaCuda]

im getting about 12-13mpg with my 318, 2.76s and 28"tall tires...that ratio is actually prolly hurting mpg on the street. And its plenty powerful...expecting high 13s...plans on dynoing it next friday..

[Chryco Psycho]

most of the engines I build do exactly that , as the engine becomes more efficient it generally increase in both power & milage unless you use 4.56 gears & a 4500 stall converter
 the biggest problem with the 318 is lack of torque , , a 360 with a good cam should get far better milage & power

[redracergt]

Ok , well I have a 360 also but it is a newer motor (like75+) and I figured the 318 would be better since it was smaller and older, but if i was to use the 360 what would be the best combo to use then since you say a 360 would be just as good?

[GoodysGotaCuda]

most of the engines I build do exactly that , as the engine becomes more efficient it generrally increase in both power & milage unless you se 4.56 gears & a 4500 stall converter
 the biggest problem with the 318 is lack of torque , , a 360 with a good cam should get far better milage & power

I have some assistance coming to help the torque on the teen...3.91suregrip within the month

[dodgetkboy78]

You should try an old quadra jet carb. They had a really small set of primaries and a huge set of secondaries. Of course it won't fit on a holley square flange manifold. You'll need a manifold that can fit it or a spacer that will convert it.

With a set of dead gears (278's) my friend and I were able to get 28 mpg on the city/highway in a worked 67 Firebird with 400 block. We were driving out to Carlisle one year.

C mon now.............Ive built and ran a few 400's.  (little finger shaking smiley guy here)

My D300 will knock off an honest 15 with no trailer, it has 4:10's
My 71 D200 would hit 17 with 3.55's
The 318 likes to rev a bit more than a 360, but, will get better economy if set up right.
(small port heads make a difference)

[Chryco Psycho]

what si the combo , what car , what weight , what gearing , do you drive in town /stop & go  or highway mostly ?

[Grancoupe]

It was a 67 Pontiac Firebird with a set of dead gears like I mentioned before. He had a Doug Nash 4 speed with an over driven 4th gear and a set of 255 60's in the rear. Nothing crazy. But the car could criuse 65 mph at 1800 rpm. It was barely chugging along. The car was worthless at the track but it was a great cruiser.

[mr_bill]

I used to have a 76 aspen 2dr with the A833 Overdrive 4.  It had a 360, with an Edelbrock performer cam, and a stock '75 manifold with a thermoquad.  I'd get 25-28mpg on the highway and it would run a solid 16.1.  Not too bad.  My 73 Challenger is getting 16mpg stock, my goal is 30.  I have a long way to go!

bill

[dodgetkboy78]

You guys sure are lucky!
71 D200, 318, and 3.55's 18 tops.
79 Magnum, mild 440, 2.76 gears, 16 tops
95 Dodge ram, 318, 518, 4X4, 15 tops (3.55's)
79 Le baron 225, 2.76's, 904, 19-20 TOPS

The only thing I have ever had that would break 20 easy is a Diesel Mercedes.
What am I doing wrong?

[Chryco Psycho]

probably the little oriental guy ... Tu Ng

[dodgetkboy78]

You lost me.