Fuel mileage questions

[Ackattack]

I'm looking to pickup some mileage and have a few questions for some of you that are doing good. See sig for my setup.

I just ordered some new jets and rods for my edelbrock carb. Hopefully that will help. How much did you jet it down (this is on a 1405). I was thinking 3 stages lean on the cruise mode and 2 1/2 stages lean on the power mode (27 on chart), and then go 1 stage rich on the secondary side. Does this sound reasonable?

I also got jets and rods to run 25 and 28




On timing: will retarding it a little help with mileage, I've heard this. I figure this will sacrifice a little power, but on a long trip would be worth it, and I can re-adjust once the trip is over.

Anyother fuel saving suggestions other than an OD tranny or fuel injection.

[68 Suburban]

It all depends on what your engine needs. I am running a 1406, which the chart is different, but if I had to pick a number on your chart that would be closes, it would be number 25. That gives you a leaner cruise range, but still gives you the power you need at WOT. If you go to lean, you will have drivability problems.

I wouldnt even mess with the secondaries. Just keep your foot out of it. You also might want to re-curve your distributor. That helped me out a bunch.

It will also depend on things like what alltitude you are at. When I am driving through the mountains near Flagsraff and Albuquerque, I could lean the carb out a lot more. I get a raw fuel smell pulling at these alltitudes. Remember, your engine looses 4% of its power for ever 1000 ft.

[68 Suburban]

I always thought that running your timing at the most advanced possible makes your engine more fuel efficient?

[lukecp]

Advancing the timing will improve mileage, and usually power too. But you must run good fuel so it won't detonate (ping).

I tried jetting my 1406 a little leaner once for power and i couldn't stand it. The truck bogged whenever i gave it gas...it did pick up a little mileage, but i did the math and i was only saving $3 a week with it jetted leaner.

So i jetted it richer and it had power again.....$3 a week is worth it, lol.

[68 Suburban]

I also forgot that changing the springs in the carb makes a big difference.

[tom hand]

You can play with the carb till you are blue in the face and you are not going to gain much as far as mpg unless you'r carb had real problems to begin with. 350's with 8.5 to 1 compression are gas hogs period. Overdrive transmissions will give the most improvement in mpg. Raising the compression of the motor with the proper cam will do some wonderful things. Crower Cams used to make a setup that ran 14 to 1 compression with a special cam and got some rally impressive mileage out of a V-8

[Ackattack]

what springs should I go to? Higher or lower vacuum? I would think the lower the spring vacuum, would be better.

Another other suggestions?

[lukecp]

The heavier the spring, the more time the metering rod will be in the up positon and be giving the carb extra fuel.