GT40 fuel tank baffels and pickup

[Steve26]

I have two questions.

1st- How do you assure that your fuel pickup will be in fuel going up or down a long hill?

2nd- What kind of internal baffels are you using?

The 60"+ long narrow tanks on a GT40 present a problem if you are going up or down a long hill, say for several miles like we have here in the Northwest. I'm working on a new chassis and would like some direction.

Any ideas? Thanks

Steve

[Alan Watkins]

Originally Posted by Steve26

1st- How do you assure that your fuel pickup will be in fuel going up or down a long hill?

2nd- What kind of internal baffels are you using?

In the reverse order:

The Superformance has three or five walls across the tank distributed evenly. There's a gap or two at the corners with area well less than a square inch. I think that prevents only tidal waves within the tank.

What I did to solve the uphill/downhill problem is have a pickup at the rear of the LH tank and the front of the RH tank, an individual pump on each, one-way valve on the output of each pumps, then tee'ed together to the carburetor.

Other advice is "don't let your fuel level get that low" or "install a holding tank (aka swirl pot) that holds enough fuel for any reasonable scenario."

[Ian Anderson]

I drive and use the left tank first, leaving the right tank full.

A couple of times I have had this problem on long down hills (pickups are at the rear) when the left tank has been between one quarter and empty. All I did was select the right tank and immediately had eno fuel starvation problem. Once the right tang gets to about half I refill.

I am running Facet red tops and when they suck air they hammer real loud and can be heard above the noise of my engine (106 db at the SVA test) these feed a swirl pot to injection so never an immediate problem.
Ian

[Bill Musarra]

Thew DRB tanks have several vertcal pieces with a narrow gap in the middle that prevents sloshing. I added a set of flappers at the rear where the pickups are. Fuel goes in but is hard pressed to leave except for overflow.



Right now, both tanks are pickup from the rear. May change to front one, rear the other. I have return lines to both tanks behind the flapper valves at the pickup points. No selector valve. Don't need one. One set of pumps is all you need. I also have a connector line at the bottom of the tanks that works to keep the levels in the tanks the same. The low pressure pump is like most regular pumps and sucking air won't hurt them if infrequently done.
Remember that if you have AN lines(8s in and 6s out) in the system, you have about a gallon of fuel that will continue to circulate from the swirl tank to the injectors/carb and back again. That should last a few miles, and that only starts when the fuel supply to the LP pump(s) runs out. If you are afraid of the return flow going to one tank more that the other, you have to have vent lines with roll-over valves installed(hope you do anyway). When the level of the one tank over fills, the valve will "float up" and occlude the line making the connector line to force fuel to the "low" tank.

Bill

[Steve26]

Thank you all for the quick response and great suggestions, I'll start building away now that I have some info. Thank you again.

Steve

[Alan Watkins]

Originally Posted by Steve26

Thank you all for the quick response and great suggestions, I'll start building away now that I have some info. Thank you again.

Steve

FWIW I think Bill Musarra's solution is by far the best. Simple, cheap, elegant, reliable (as long as the swinging door doesn't stick shut for some reason).