problem i had with Just the check valve, is after a bit of time, the engine would rich bog due to overpressureizing the tank. the extra pressure will do one of 2 things, either eventually pop the lid, or like i had happen, it would flood the engine. thats why i say you ll need both the check valve AND the relief valve. check it out, typically with these engines you ll get max 12 lbs of pressure in the tank. MOST common is about 8, pretty much as hard as you can blow into the pressure line. you start putting more pressure behind a fluid, that fliud will flow faster, and be pushed thru smaller areas at more volume, thus flooding these nitro engines. i could nt find a releife vavle small enough 3 months ago when i was tring to get one, so i set the project aside and started playing with the plane and heli, and now got the Baja. so the projects shelfed prolly till fall, or really crappy weather times... if you can find a small relief valve and set it to release pressre over 8.5 to 10 lbs. life would be fine as long as your fuel system is air tight. like thats a big change for nitro.
Timmahh