I should say when I tested my snorkelers with holes in the combustion chamber, they didn't like it. And I shouldn't have referred to them as draft engines really as the proportions of a draft engine are different. When I put a 3 foot length of big 2 inch diameter plumbing pipe on my piglet snorkeler, it gives the gases more freedom. I never got it to sustain in snorkel mode but it did make some very loud cannon noises and I worried about the police coming to visit. ha
The thing about "fuel pooled" engines is that you can't have extreme combustion or else the fuel will fly about too wildly and destroy any steady state fueling. Another thing about "fuel pooled" snorkelers and draft engines is that the thrust is not really very functional as a toy unless you are hot air ballooning or spinning tennis balls. ha
(I should say it would be nice to have them run as well in the horizontal as they do in the vertical.)
I remember putting a large washer in the front end of some of my typical homemade plumbing pipe pulsejets with typical Dynajet proportions. The washer would if you primed the engine and lit the front end, would go off like a gunshot, the flat face acting as some kind of reflector. Long ago I made a growly valveless/draft engine of sorts out of a 4 inch sphere with a long piece of pipe threaded into one end and the opposite side of the sphere just a hole. When "fuel pooled" and held at a 45 degree angle with the tail up it, the arrangement would rev up to a high speed but it was weak in thrust.
I have a 3 foot length of titanium tubing about 1.75 inches in diameter and another of the same lenght 2.5 inches in diameter. And I also have some 1 inch diameter and a few pieces in the 1/2 inch size, one piece is 6 feet long I think. Then I have a small bundle of 1/4 inch titanium tubing too. The 1.75 inch diameter stuff is an amazing .020ths thickness so it is very light. And I suppose since titanium is kind of reactive with very hot air, a snorkeler would be a better choice than a pulsejet. But I have no way to transition the pieces or weld some toy of sorts together. I think titanium would be ideal for a cooler running snorkeler if you needed something light that could fly or propel itself along.
"Titanium burns in air when heated to 1,200 °C (2,190 °F) and in pure oxygen when heated to 610 °C (1,130 °F) or higher, forming titanium dioxide. As a result, the metal cannot be melted in open air as it burns before the melting point is reached, so melting is only possible in an inert atmosphere or in a vacuum." "It is also one of the few elements that burns in pure nitrogen gas..."
I ran across this tidbit on flue gas stacks, perhaps vaguely of interest.
"Cooling was carried out by cycling fuel behind the titanium surfaces at the front of the wings (chines)."
"When we become rich and shameless a thin walled titanium unit will do."
Maybe one day. Oh!