Cool! This is conceptually very similar to the factory's flood-stop kit, only the bleed-off holes in the flood-stop fittings were true pinholes, considerably smaller than 0.025". The reason the hole size wants to be really small is that with a significantly larger hole, your pump's efficacy is going to take a serious hit when you have to drag fuel all the way up to the engine from the tank, because the pressure bleed will become a vacuum bleed. Not only will the pump not be able to apply as much suction to the inlet line as it could without the bleed, but the bleed will also allow the fuel inlet line to drain all the way back to the tank. This could make it difficult to start the engine after it's been sitting long enough for the fuel in the carb to evaporate. Keep an eye on it...you may want to make up a new set of fittings or make a pinholed restrictor and force it into the return line.

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Too many people who were born on third base actually believe they've hit a triple.

It may be easier to use a very sharp pointed punch and punch a piece of brass until there is a tiny crack on the other side. Then soldier it into the tee.

With a new set of drills there may be one smaller than .025. I’ve broken a few just cleaning orifices and I broke the .025 drilling this hole - by hand. It would be extremely hard to drill a smaller hole . At least, I think it would.

There are a couple of things that one could try though. I could drill a larger hole, .040 is pretty easy. Then soldier it closed with some soft lead soldier - then drill the soldier instead of the brass. It would still be pretty tough.

Or, drill with a larger drill and stop just as it breaks through, hopefully leaving only a pin hole. Or drill until there is only a thinner than paper bottom in the hole and drive a darn pin through it. Both of these would involve a lot of nipping and tucking and starting over. You can't see the bottom of the hole and you can't measure the depth with any accuracy.

I did this one backwards so I could use the screw threads to hold on to. I drilled it, essentially, from inside the tee before I brazed it on. After I cut off the screw part, I filed carefully, hoping to stop when it was only a pinhole. It could work. Mine didn’t. I think I had a flat bottomed hole because the drill broke.

If I have trouble at this point, I’ll try soldiering half of the hole (that would be mostly luck) - or all of the above. I really don't like my options so far. I'm liking the punch idea best.

(I also have enough new fuel hose to give up if it gets too hairy)

Danny

How about using one of the later model fuel filters that already have the bleeder fitting? And definitely return fuel to the tank, not the pump inlet. If it is kept as close to the carb as possible it should help hot running too by bleeding off vapour and preventing vapour lock. Just a thought.

Are you using a pinvise? I have had no trouble drilling some very small holes in two stroke carbs using one. Any other way can be almost impossible. They are not expensive.

A pin vise is what I’m using but I had forgotten what it was called. Thanks for reminding me.

I looked one up on the internet. It has 6 bits from #52 to #80, it doesn’t say which bits it includes, but # 80 is the smallest at .0135. A needle from your sewing kit measures about .030.

I know, it has to be possible. They make a drill that size so there is a hole that size somewhere on the planet and someone knows how to drill it. It would be easier to enlarge a smaller hole than to drill a new one but I don’t think I’m capable of drilling a .013 hole in brass. I may try it and prove myself wrong but I think a drilled hole, this size, could make this part cost around $4 million dollars. I'm just guessing.

I’m not sure if that would help me, though. From what Dan has said I’m assuming that .013 is still too large. He’s talking about a mythical hole. A hole that isn’t really a hole. A hole you can’t blow through or see through or even see IT with the naked eye. It’s so small that it can’t be measured. It’s a pin hole.

He seems reasonable enough though. I’m assuming he’ll give me a tolerance of + - .000000000001.

The three nipple filters have a HUGE hole -.050 or .060.

That works well for either type of system (high side to low side as has been done in this case, or high side to fuel tank as the factory did on vehicles originally equipped with the 3-nipple filter). If the 3-nipple filter is used in a retrofit system, the vapour bleed should either be piped all the way back to the tank as you suggest, or there should be a very small, pinhole-sized restrictor orifice between the high side bleedoff and the low side, to prevent the problems previously mentioned.

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Too many people who were born on third base actually believe they've hit a triple.

Dan,

I’ve been thinking again. When I removed the line to replace the pump, mine wanted to siphon toward the carburetor. I’ve had the same problem with other old trucks with the tank behind the seat. Some are nice and give you a screw-on fitting at the tank so you can loosen it enough to break the seal until repairs are done but Dodge has a rubber hose connection that is now dried hard and immovable. I had to plug the line at the frame.

It’s still a problem to figure out for the poor souls with rear mounted tanks but doesn’t it sound like it wouldn’t be a problem for me? After shut-down, there would be gravity fed pressure toward the carb — wouldn’t it? Or am I looking at it wrong?

Danny