Technical Tips

Stainless Steel Gas Tank

Greg Dembs has constructed an enlarged stainless steel gas tank for his 2500M. He has squared off the top to increase capacity. He includes an Autocad drawing of the old and new tanks. He reports:

The measurements I used for the OEM tank in the drawing are from my 1974 2500M (chassis #2948 TM). The measurements were taken from the outside. I made the new tank slightly bigger because I knew I had the extra clearance.

The tank and new mounting straps were fabricated by Rock Valley Antique Auto Parts in Stillman Valley, Illinois- phone 800-344-1934

We added some foam for additional safety if rear ended. The foam becomes stiff like dense styrofoam after drying. Ideally, one would weld a U-shaped steel tube to the rear upper steel tubes in front of the tank that would rap around the back of the tank and pick up the bumper bolts (heaven forbid the rear bumpers were more than decorations attached to the fiberglass!). Also, with foam on 3 sides, should one or both of the tank straps break loose from the fiberglass tub, the tank would still be held in place. It also deadens my excessive exhaust noise a tad.

Rock Valley made the new straps and pre bent them for me to conform to the shape of the tank.

It handles fine. I don't notice much difference, but I haven't had a chance to really thrash it yet. The new tank only weighs about 10 lbs. max. more than the OEM. I'm getting about 3 additional gallons of gas in (3 x 8.3lbs?=25lbs) so the total weight gain with full tank is 35lbs. As mentioned, they installed 1 baffle. (The factory tank appears to have a baffle 1/3 of the way across (peering through the sender hole) where one of the two ridges is, so I assume there is a second one at the other ridge. -Webmaster)

(Looking at the pictures I think that the space behind the tank is better empty so it provides crush space. -Webmaster) The Autocad drawing (a .dwg file) is available here. A pdf file is here pdf.

I got most of my info from Brian Weymeier as he did a similar installation a few years ago. -Greg Dembs


Usefull Conversion Factors
1 gal. U.S.231 in33.785 liters
1 gal. Imp.277.42 in34.546 liters

Water weighs 62.4 lbs per ft3 (at standard temperature and pressure), 8.34 lbs per gal. Gasoline (petrol) weighs less than water. The exact weight of a gallon of gasoline depends the blend of hydrocarbons and addatives used as well as the temperature of the gasoline.

The U.S. gallon is the old English wine gallon (officially Queen Anne's Gallon) standardized in 1707. Queen Anne's gallon is a volume containing exactly eight pounds of wine. 'The pint is a pound the world around', you see. The U.S. dry gallon is the old English wheat gallon A.K.A. the William III gallon (1696) which contains eight pounds of wheat. There was also an ale gallon containing (can you guess?) eight pounds of beer. This was standardized in the reign of Queen Elizabeth I.

This fixation on weight seems to be because it is much easier to measure the empty and full weights of a jug than to measure the volume through the mouth of the jug.

In an attempt at decimalization Victorian scientists created the Imperial gallon contatining (wait for it) ten pounds of water. Of course there are still only eight Imperial pints in an Imperial gallon.

Last updated on July 5 2007.