Fuel Tanks

David Large · Post by **David Large** » Sat May 12, 2007 7:10 pm

At the moment i am doing some long outstanding upgrades on my beloved BRA. I have had it on the road for 18 years so I guess it is time I finished it.

The fuel tank has always seemed pathetically small. I have measured it and calculate the volume at 49 litres but I never seem able to get more than 30 - 35 litres in it. When the fuel gauge gets to empty it runs out!

I am thinking of having a new tank fabricated to give me 70 litres.

What capacity tanks do you have in the Hawks?

Any other BRA owners out there with a view on this?

Cheers

Post by **clive** » Sat May 12, 2007 9:28 pm

Hi David I have the Hawk stainless steel tank and I reckon it holds 8 gallons (30L) If your tank is anything like the Hawk one it is deeper at the top so if you are calculating the capacity by multiplying the height, width and depth at the top you'll get too big a reading. Measure the depth half way up the tank and see what you get.

David Large · Post by **David Large** » Sat May 12, 2007 10:48 pm

Clive, I am allowing for the sectional shape of the tank and taking the averagewidth of the tank, multiplying that by the height and the length.
So at 30 litres you have a range of about 130 - 150 miles when driving economically and 100 miles when enjoying yourself!
Cheers

Post by **clive** » Sat May 12, 2007 11:38 pm

Those figures are about right for me with the Ford 302 and Holley Street Avenger Carb. The Rover engine tends to be more economical though giving around 30 mpg!

Roger King · Post by **Roger King** » Sun May 13, 2007 12:21 am

330 bhp 289 HiPo with Edelbrock heads, Compcams 268H, Edelbrock 600 vacuum, Unilite dist etc. gets just about 200 from a tankful. Mind you, it depends what you're doing - 10 laps of Hockenheim returned about 4-5 mpg, and the T5's 0.68 top gear gives over 20 on the motorways.

Roger

David Large · Post by **David Large** » Sun May 13, 2007 6:00 am

My Rover (4.0 litre / stage 2 heads / fast road cam / Weber 500) I think certainly will do towards 30mpg at a steady 70 mph but do anything else and the consumption increases dramatically.

My tank (external dims) is:-

depth across the top = 355mm
depth across the bottom= 210mm
Vertical height = 230mm
Length across the car = 760mm

Therefore:

(355+210) / 2 x 230 x 760 / 1000 /1000 = 49.38 litres

Say 49 litres / 4.546 = 10.8 gallons @ 20mpg average = 215 miles.

I never get near that. Nor when I fill it do I ever really get more than 30 litres in it.

There is another oddity with my tank. If when I fill it up I submerge the base of the filler pipe where it passes into the tank, it must be trapping air because after a few moments, if the car is left standing, petrol gushes up the filler pipe, through the breather in the cap and onto the back of the car. There is a very very slight depression in the top of the tank around the filler neck and I suspect the filler pipe projects into the tank which would also lead to trapping air.

Sorry if this is all boring but I am trying to solve some irritating little niggles. I have managed with this for 18 years so in the scheme of things it is not that important, but with age and grumpiness comes an even bigger desire to have things right.

Cheers.

David

David Large · Post by **David Large** » Sun May 13, 2007 6:15 am

clive wrote:Hi David I have the Hawk stainless steel tank and I reckon it holds 8 gallons (30L) If your tank is anything like the Hawk one it is deeper at the top so if you are calculating the capacity by multiplying the height, width and depth at the top you'll get too big a reading. Measure the depth half way up the tank and see what you get.

Clive, forgive me for being pedantic here but at 1 gallon = 4.546 litres

8 gallons = 36.3 litres
and
30 litres = 6.6 gallons

There is a 20% plus variation here which will skew things a bit.

I probably need to go out more and try to discover a life!

Anway, I am going to try to get the tank out of my car this week and have a bigger one made.

cheers,

Post by **clive** » Sun May 13, 2007 10:24 am

Sorry DL, My mistake. I converted from Litres to US instead of Imperial gallons. Should be as you say 8 imp gals = 36.368 L.
I find when filling my tank it takes a wee while for the fuel to flow past the baffles. when the tank is fiiled to the bottom of the filler neck if you wait a few secs it will take more fuel, fill up and go down again several times.
You will also have to take into consideration the wall/baffle thickness, the float displacement and the unused quantity remaining in the bottom of the tank (governed by the height of the outlet pipe) to get the true useable capacity.

Roger King · Post by **Roger King** » Sun May 13, 2007 10:28 am

I seem to remember Gerry saying the later tanks were larger, when I bought mine - might be worth asking him.

Roger

Wynterburne · Post by **Wynterburne** » Sun May 13, 2007 12:16 pm

Hi

Have a chat with Colin Newbold about his solution - fuel to spare!! Literally.

Regards

Richard