Mk2 Balance Pipe - Fuel Tanks

[Troy]

As I understand it, MkII cars had just one filler. Does anyone know the size of the balance pipe to the opposite side tank?

 

[Troy]

Do I have it right? MkII's did run two tanks, but with just one filler?

 

[Mike Drew]

Only a handful of GT40s ran with a single filler--the Gulf Mk 1 cars in their later iterations (as far as I know). The Mk 2 cars had dual fillers. Here's an image from the GT40 parts book of the road car fuel system:

I believe that the Mk 2s used the same system?

A handful of cars were modified to have very effective crossovers; if my memory serves me correctly, P/1040 had a large-diameter oval-section rubber hose running right through the cockpit, just ahead of the seats, connecting the two tanks, but it retained dual fillers.

 

[Troy]

Thanks Mike, handy info

I believe (at least) the Gold MkII from '66 LeMans had only 1 filler...

 

[Troy]

Did all 1966 LeMans cars have only 1?

 

[Seymour Snerd]

Here's a drawing from the Mk II SAE papers:

 

[Troy]

Thanks Alan, that confirms what I suspected from these 3 Mirage pictures.

Opennings in the inner sills on both sides, and one pic even shows what could be the cross - over pipe in question.

I appreciate the info.

 

[Seymour Snerd]

Opennings in the inner sills on both sides, and one pic even shows what could be the cross - over pipe in question..

So it's a big pipe running under the driver's knees. I always wondered. Thanks.

 

[Troy]

Yep, looks that way (also as Mike poited out above). Even at 4" diameter, that pipe would hold the best part of 10trs of fuel on it's own.

 

[Cliff Beer]

It doesn't need to be a big pipe. In fact, it's better if it isn't....for purposes of baffling from side to side, smaller is better. All that's necessary is a pipe with a flow rate sufficient to fuel 1/2 the consumptive flow of the engine at WOT (plus, say, another 50% just to be generous). A single one inch pipe would be plenty large.

 

[Troy]

That, and who wants a dirty great big 4" fuel line running under their knees!

Mine is 1-3/4" and runs behind the main bulkhead, in front of the engine.

 

[Bill Musarra]

I have a small 3/8" line that runs underneath the car(wash board pattern) and with the motor running and the return lines to both tanks, the fuel gauge(in the right hand tank) is a little behind. By that I mean when I turn the engine off the fuel level rises ever so slightly. I believe the key is to have the return line going to BOTH tanks. Next year I plan to add a pickup line from both tanks rather than just the right hand one. Dimis car is the one I patterned it after. I can supply a drawing and explanation if anyone is interested.

Bill

 

[Seymour Snerd]

It doesn't need to be a big pipe. In fact, it's better if it isn't.

Yes, well, everyone knows Ford was completely clueless in developing the Mk II.

:stunned:

 

[JimmyMac]

Yes, well, everyone knows Ford was completely clueless in developing the Mk II.

:stunned:

Cliff,
I would submit that it does need to be a big pipe.
That four inch crossover is necessary for filling both sponsons from one inlet as fast as possible during pit stops.

 

[Seymour Snerd]

Cliff,
I would submit that it does need to be a big pipe.
That four inch crossover is necessary for filling both sponsons from one inlet as fast as possible during pit stops.

Another consideration might be that since this car is designed for "circuit" racing, and that takes place (by definition) over an essentially circular track, if you have a small crossover tube the fuel will migrate to the "outside", and the prodominately inside tank will empty first. If you have a fuel pump at each tank and check valves on your fuel pumps you can (kinda) ignore this, although the inside fuel pump may not like pumping air for most of the race.

Either way, as the race goes on the lateral center of gravity of the car gradually shifts to the outside. Probably not really what you want, especially in a 2,700 lb car with a pair of 22 gal (~130 lb) tanks.

 

[JimmyMac]

Another consideration might be that since this car is designed for "circuit" racing, and that takes place (by definition) over an essentially circular track,

Forgive me, I was thinking all this time that this car was designed for the Mulsanne Straight.

 

[Seymour Snerd]

Forgive me, I was thinking all this time that this car was designed for the Mulsanne Straight.

Only if it alternates the direction of the U turn at the end....:lipsrsealed:

 

[Cliff Beer]

Cliff,
I would submit that it does need to be a big pipe.
That four inch crossover is necessary for filling both sponsons from one inlet as fast as possible during pit stops.

Ah, yes, right you are. With a single fuel filler, and when racing on a track, then a big ole' pipe would indeed be absolutely necessary....

Personally, I seem to do more school runs and trips to the plumbing store than pit stops at LeMans so I guess I can stick with the dinky 1" line I have!

Cheers!

 

[Ian Anderson]

Back in the mid / late 1960's I seem to remember a story about having a maximum tank capacity.

Now a 4 inch pipe connector would not be part of the tank and possibly hold a couple of gallons - enough to do an extra lap between fill ups

Of course I could also be very wrong on this!

Ian

 

[René]

you could make balance pipe with a sort Tap or valve? in it so when you need a fast fill up in both tanks you can open it wide,
but when you race you almost close it so in case of cornering not all the petrol goes to fast to the other side, otherwise it can disturb road-holdings/balance.