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GT40 Tech - Engines/Induction/ExhaustMotors and engine related - right here!
I can't find any post on this subject but please route me if there has been a thread before.
Because the GT40 fuel tank is long, narrow and runs front to rear, there can be an issue with trapped air. If you have fairly full tanks and park on an incline with the front lower than the back you will have a pocket of air behind the fuel can push it up and even out of the fuel fillers. I have experienced this and some others too.
I had fitted tank breathers at the rear of the tank, but despite their high price (£20 each) they still allowed fuel to leak on acceleration. In any case you ideally need a decent breather at the rear to allow easier filling at the gas/filling station.
I am looking for a good solution and wonder what others have tried and found successful. Clearly it needs to be safe and avoid fumes into the cockpit.
What we did was to add a check valve and 5 or 6 feet of hose after the valve. Bring the hose as high up in the chassis as you can, usually along the rear bulkhead and back down and into one of the sponsons in the engine compartment.The check valve is the type that allows air in both directions but closes in a rollover situation or with a surge of liquod.We have a non vented cap so this is what we use to allow air in and out of the tank. If you route the hose right you might not need the check valve.
I also found that a check valve solved this problem. In the end I went to an off-road bike/ATV store and bought a check valve for about $10.
My breather pipe is located at the front of the tank, and I mounted the check valve at the same height as the filler cap, attached to the vent pipe by a length of rubber hose.
Since adding this in, I haven't had any fuel spillages and petrol odour is less (using downdraught Dellortos mean you always smell it a bit).
We breath our tanks through two carbon canisters (one per tank) and these are then controlled and "dumped" into the inlet manifold at high throttle positions. The plumbing for the canisters is critical as the effect of the fuel slushing in the tanks can over fill the carbon canisters and this must be avoided. Again a lot of work has been carried out in this area at Roaring Forties because of the Australian Design Rules and I believe we have it right (cars have been FULLY evaporative tested).
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