I didn't say you should send YOUR jets out and have them flowed. But I sure wouldn't drill them, just my opinion. Lippy
I've gone so far as to solder jets shut and then drilled them a bit smaller when I needed to lean the mix.
Jets have been drilled since jets have been around. It wasn't always easy to find jets. Now there are sets available so it might be wise to use factory jets just to avoid confusion over what size they are if you change for atmospheric conditions in racing. For a show car, it will likely be a one time thing. A set of drills is cheaper.
Three years from now you WILL not remember what size those jets were drilled. I throw out any jets that have been drilled. If you look closely at some Holley jets they have a chamfer, so do not, same number......You can buy any size jet for your Stromberg online......
I looked into it when doing some carburetor tuning, it seemed to me for temporary use it's OK, to save a little money. Drill them out as required, and when the AFR is where you want it purchase the "real" numbered jet size that corresponds to drill size for permanent use. Holley jets are the same (drill size and jet size) up to around #70, but then everything goes off the reservation. Some people acted as if I would push their grandmother down the stairs for even suggesting this. Thing is though, jets are flowed first and then stamped with a number. One reason they don't recommend drilling, even though they might be drilled to a larger diameter it's not unusual for them to actually flow less. A factory 47 on the high side may flow more than a factory 48 on the low side I think they have 3-digit jets if ya wanna get precision. I don't think it matters too much for most of us.
Some aftermarket jets come with no numbers at all, they're blanks to drill the size you want. I have a hand full of old jets and I wouldn't trust the numbers stamped on any of them. Would you? Sent from my iPad using The H.A.M.B. mobile app
Don't sweat drilling jets. Just do it right. Or as nicely as you can. Because really how do you think the manufacturer got the holes in there? I have done a few sets. I hold them in the drill chuck on the tailstock of the lathe and put the drill bit in the lathe chuck. Nice and easy to hold onto and control any run out in the bit.
Hey Pal--- I'm curious of what the AFR read from the home grown jets to the wiz-bang precision jets. I wish I had a ARF I'd check my hand full of clunkers and turn them into precision pieces ️. Sent from my iPad using The H.A.M.B. mobile app
Also if your tuning to your meter and get to where you want to be. What would you gain by purchasing jets the size you just got finished with? A number on the jet and a hole in your wallet is all. Sent from my iPad using The H.A.M.B. mobile app
Well do what you want, I don't give a fuck. I'm just trying to explain tuning strategies, what has worked for me. Some people just bolt on any carb that fits, and so long as it starts and runs, they're cool with it. That's fine too. This is a hobby for me, my wallet has had plenty of holes drilled in it. I like how my engine runs, I'm not trying to "save" money, just not spend more than necessary. Precision jets are going to flow equally side to side, the drilled jets just ballpark the AFR. Sometimes, really picky tuners will install mismatched jets to even things out. A wideband O2 sensor is really the only way to fly if you're tuning a carburetor. Trust Me.
It wouldn't bother me to drill jets. If the flow is not as good a jet of the same size that has not been drill.....what difference would it make if say you had to larger to get it to flow an un drilled jet. If you are tuning by the way the park plugs look.....I would drill to get it right and just drive the shit out of it. I understand that a wide band O2 would be a handy tool for tuning but just for argument sake's what did the guys do back in the day that they didn't have this fancy tuning aids. Guess they never set any records back in the day.
It is the chamfers that assist in flow, not just a hole. Precision work is very rewarding once you get it right. Try 2 stroke snowmobile tuning. Then once you think the motor's right get after the clutch tuning. Yes, clutch tuning. Then you can make even more power with the engine, then shortly after the greed sets in (much like N2O tuning) you reward yourself with new engine parts I always did my tune on the track with jets and plug color. It's almost like sex (almost!) when you find a tenth with wrenches and plugs and jets. At the end of it all for me I went with the best safe "good air" tune and left it alone for "bad air" and made the change with shoe polish. Yeah bracket racing, or what I call a 1/4 mile casino. Frankly we shouldn't piss on each other's legs when advice is shared. There's some really saavy cats in here that share what's taken years and parts galore to end up with. Better to be nice like our grand parents were and say thanks. Just sayin, and good luck with tuning but you're a dick if you don't show us the "win".
One thing they did, was get about 10 miles per gallon, instead of 18. Drag racers, of course don't care about fuel economy. They don't care about "part throttle" because they don't use it. No vacuum advance, because all they do is wide open throttle. Most people don't want to get off in the weeds with carburetor tuning either. I was just interested in how to increase the range on a tank of juice, mostly. What's interesting to me at least, fuel economy and performance aren't at odds with each other. The carb circuits that make it go fast don't have much if anything at all to do with steady cruise fuel economy. What a wideband does, along with a good understanding of how carburetors actually work, is allows for a ride that will both smoke the tires and get respectable mileage. I agree experienced mechanics probably didn't need an AFR meter, but one of the ways they became experienced was nuking pistons. They wideband meters save time and guessing and will pay for themselves pretty quick on a long trip.
My buddy's old man had a tune-up, electrical business he opened in the late 40's in Detroit. I recall him saying they drilled out jets all the time. Neighborhood hot rodders kept him busy. I asked to borrow them in the late 80's to richen up the carbs on my motorcycle after I installed a header on it. Took him a while to find them since they hadn't been used in a long time. Wonderful set of tools.
The Jalopy Journal
