for the sbc 350 equipped flatties

What kind of gas mileage are you getting? Im running a 4 speed tranny with 3.54 gearing. Im running the original under seat gas tank and Im curious how quickly Im gonna go through a tank of gas.

 

I get about 17-18 on the highway and probably less than 10 on the trail, with 4.10's, 33's, an overdrive, and an additional 31 cubes. The 11 gallon tank didn't cut it.

 

Don't you have a gauge? It would not be hard to measure the mileage.

A lot will depend on your driving habits. I expect you can visit a wide range just by the way you drive.

 

Its not on the road just yet, only a few test drives, guess I could have mentioned that in the beginning.

 

QFT.

No idea what mine will be getting, but it's not a 350....


With my truck my dad was getting 16 around town.... As soon as I got it it went down to 13.... Just love that small block sound... He never got it over 4000 rpm.

 

^This.
I can get anywhere from 15 to 5 MPG, even less, depending on how much load pedal it gets.

 

Yikes! Im going with a secondary fuel tank.

 

A sbc powered Jeep can really make an OD shine-one big reason to keep the D18. I think the OD is the only reason I get relatively decent highway mileage as when engaged, the engine is usually just loafing along thinking it is turning a set of 3.07 gears. I ran a Confer rear tank with two jerry cans for a couple of decades. That said, from a safety standpoint, I really did not like jerry cans on the back and didn't care much for the stock tank for the same reason. It is not difficult to fit an 18-20 gallon tank in the rear. The 25 gal one I built took a bit of frame component rearranging.

 

Good point, OD would make a difference.
At least I’m hoping it does.
Oh and “load” = “loud”, pardon my poor spelling.

 

would like to see this set up. do you have pics?

 

Classic case of "I should have taken pics" but didn't before the install. You can sort of see the 25 gal tank on these:





The filler neck and filler "garage" (door assembly is modified CSI for Chev/GMC):







To get the tank in, the body mounts off the center cross member were outboarded, along with the rear cross member. There are machined steel frame inserts inside the frame rails (about 9" long if I remember correctly) to which the new rear cross member is bolted, along with the roll bar mounts visible in the first photo. The body is lifted 1" and all the tank connections run above the center cross member.

As a side note, for the tank connections, I weld in a NPT bung of the desired size (usually 3/8 or 1/2 NPT using machined steel reducer bushings) and then use brass compression fittings for the lines, with the fitting drilled just enough to allow the line to pass completely through. You can then put a filter sock or brass screen on the end of the pickup tube and still remove it for maintenance and it also lets you bend the pickup tube so you can position the pickup where you want it at the tank bottom. The tank vent, via a Summit tip-over valve, and the rear diff breather are both located in the "garage". Clear as mud?

Here are a couple of shots of a similar tank we put together for my buddy's Willys wagon:

 

very useful info. thanks