Howdy!!! I have a Fox 74 2 stroke mounted sideways on a TF AT6. The fuel always blows out of the mouth of the carb and onto the head- gets things all gunky (with castor in the fuel mix) when it hits the hot head of the engine. Can I fabricate a velocity stack of some sort to keep the fuel from blowing out?If so, how long would you make it?
Also, just exactly what does a velocity stack do? I have seen them on dragsters and race cars but dont know anything about them
Thanks All!!! John McGowan

Essentially, on your engine, it will help solve the problem you just mentioned. Make it look about right.

On some of the competition type engines you have mentioned, they are of a very precise shape, length, and volume. They will have a tuned effect on the intake charge at wide open throttle.

John, before you go to all this trouble, try a smaller prop on the engine and let it turn up a little more rpm? It may swallow most of this without any more bother?

enjoy,

Jim

Hi Jim!!! I had a 12x8 prop on it when it was doing this.The engine was tuning up in the air but going nowhere if you know what I mean. I then changed to a 13x6 and as Emeril on tv says: BAM...
BAM-BAM!!! It made all the difference in the world on this plane as far as speed and overall flying
I will do as you say and "make one that looks about right" . Thanks Jim and take care!!!!
John

John, I played with this on a Fox .50 I converted to Diesel. But, instead of putting a velocity stack on it, I raised the carb up 3/8 inch by putting an adapter under it that I made out of three 1/8 inch plates, not only did the fuel stop spraying out of the carb but I gained 200 rpm. I made the diameter of the hole in the plates the same as the venturi to keep the air/fuel velocity up.

Good idea Dave !!! If the homemade stack doesnt
work I will give your method a shot.
Glad I thought of that huh??
Thanks Dave!! John

John:

I run Fox .74's myself. Have settled on either 13x6 or 14x4 for prop selection. Yea, all my Fox's spray fuel from the carb out. More so it seems with the air-bleed carbs than the older Mk-X. However, you can lessen this if you run an air-cleaner on the carb! You should not see any RPM drop or any other problems (I don't). If you are careful, you can get one of those rubber cup/plasic screen insert ones to fit over the carb if you use some glycerin or silicone first then secure it with a wire or twist tie. A piece of pantyhose or stocking also works. I use a small rubber band to secure mine (hose on the carb that is). Seems to work fine for me. Much less fuel spray. You might give it a shot before you start to fabricate a velocity stack. I use two thicknesses of hose.

If I could figure out how to chrome plate the panty hose material I would have it made. Agreed, the setup doesn't look that great but, as I said, it appears to work.

Dan

I've noticed that carbs that have needles or
tubes that go all the way across the opening
don't spray back much and ones that have
a jet tube that only go half across like
the Fox EZ and Perry do spray back.
Keep your eye peeled and see what you think.