Soldering/drilling jets?

[ArizonaGuy]

10-32 air bleeds, sure. But how about primary & secondary Holley jets?

[ArizonaGuy]

I’m tinkering around with a itty bitty carb for an itty bitty motor, the ‘right’ jets won’t be here until the end of the week at the earliest. I was hoping to have this buttoned up in the next day or so. Is there any harm in making my own?

[jeff swisher]

I have drilled a lot of jets and even tried to match the size in a holley jet kit and nothing ran as well as the drilled jets.
Yea odd I know.

I have also soldered jets closed and redrilled them and I have even stuck a small copper wire into jets to reduce the flow when aftermarket ones are not available.

I do like the wire method.
Take a speaker wire or extension cord and strip the copper from it and measure the diameter of the wire.

You can stretch the copper wire also and reduce the diameter by .0005" at a time if you wish.

In a motorcraft 2 barrel i would run one long wire each end in a jet and twist a loop in the middle to secure the wire.
Worked perfectly.

[HQM383]

No harm. It just might be hit and miss and take several tries as you don’t know what the jets flow after drilling. The carb doesn’t care about number stamp or hole size, just the flow and pressure differential.

[hoodeng]

A lot of carburetor jet manufacturers use numbering systems that rate the flow of the jet under control conditions, not the actual diameter of the hole, even though these two factors can correlate. If the number of the hole coincides with a drill size, that hole is typically produced under a controlled process so the manufacturer can trust its operation in the field.

Drilling jets is a process that has worked well for a lot of guys over a lot of years. But, if you want to keep your results linear to the numbers involved, using the OEM jets probably reduces variability.

I am interested how a drilled Jet out performed the original Holley jets?, this suggests the drilled jet is behaving differently, maybe this is what the engine wanted regardless of what process is used to produce the jet?

I knew owners of British race bikes back in the seventies that had only four main jets in their toolbox, two were in the bike, the other two were getting soldered and drilled.

Cheers.

[modok]

The right size drilled jet is better than the wrong size OEM one.

Also on a long enough timeline nothing is constant.
You check a 50 year old carb jet it's not unusual to find it has grown or shrunk a few sizes.

[HQM383]

For reference

[quickd100]

Holley carbs have countless jet kits available for them. On the other hand a Carter Thermoquad had a very limited supply for aftermarket jetting supplies. I have no problem drilling an soldiering jets for such a beast and have had good luck doing so. I am usually using a LM-2 A/F meter and or a Dyno to get things as close as possible.

[F-BIRD'88]

When drilling your jets, after drilling the hole select a bigger drill bit and lightly bevel the entrance and exit (front and back) of the jet hole... This breaks the sharp edge of the new drilled hole. Now it will flow relative to the drilled size.. You're going to check the result with a AFR guage anyway. (At least as a you're too lean warning device)

[ArizonaGuy]

Well sh*t howdy, that worked pretty good. Backsides countersunk also

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[jsgarage]

I use(d) soldered and drilled jets to dial in sets of carbs especially when not much info was available on the combo. Worked well when combined with a plug cut, but I then always ordered factory jets of a size indicated by my hand drilled soldered jets. I tend to tune for longevity and 50:50 solder is not very tough.

[jmarkaudio]

While it may work... Holley jets are a square edge orifice jet. It's flow characteristics are based on having a square entrance, and the flow is based on the length and diameter of the passage. It is possible to have a bigger passage diameter and flow less. Opening up a jet may actually decrease flow with the square entrance maintained. I do not suggest drilling them. Other jets like BLP or Maxjets are tapered on the entrance and exit so reaming them larger is usually not a factor.

[ArizonaGuy]

It may or may not be ‘ideal’, but it did get me out of a bind. Probably not something I’ll make a regular habit of practicing, but it served its purpose