Zenith 1 main jet

[1930marie]

Who supplies calibrated jets and or the drill bits? I am needing both a #61 & a #62 main jet for the Zenith 1. I would also like to buy a good quality set of the drill bits. Thanks!

[HoarseWhisperer]

Calibrated: http://www.rennerscorner.com/carburetor.html

[1930artdeco]

Any good hardware store should carry them as that is where I got mine.

Mike

[Chuck Sea/Tac]

Or a hobby shop. And don't forget the pin vise.

[1930marie]

Thanks everyone - hotter plugs were an excellent tip. The aftermkt. 63 main jet at 700 ft. is just to rich for my motor. Checked compression and even though the carb passed the flow test with flying colors, a 61 or 62 is where it needs to be. Thanks again for the help, I have six aftermkt main jets calling for me to choke em down!

[Tom Wesenberg]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by 1930marie

Thanks everyone - hotter plugs were an excellent tip. The aftermkt. 63 main jet at 700 ft. is just to rich for my motor. Checked compression and even though the carb passed the flow test with flying colors, a 61 or 62 is where it needs to be. Thanks again for the help, I have six aftermkt main jets calling for me to choke em down!

Years ago I used one or two strands of fine copper wire inserted into the main jets to lean out the carb. I even tried it on my 1962 Chevy 283 with overdrive, but that car still never would get over 18 MPG, which was the same as my other 1962 Chevy with 283 automatic. The copper strands did improve some customers MoPars running.

[redmodelt]

Seems to me I read someplace, it's not just the diameter of the hole but also it's length that sets flow.

[JD 1931]

I got a set of the very small bits off Amazon, around $5...

[Benson]

Originally Posted by redmodelt

Seems to me I read someplace, it's not just the diameter of the hole but also it's length that sets flow.

Very true ... this is why soldering up jets and re-drilling holes yields such varying results ... with flow rates all over the place.

It is almost impossible to get the solder to the exact same depth every time.

[Ron in Quincy]

I prefer to use original jets; inspect the tip to be sure it is not damaged. Have found over the years that Zenith and Holley single venture original carbs the main jet was a #19 and the opening was .037.
I do not solder up and re-drill jets, just the way I do, others may not agree !!!

Ron

[Tom Wesenberg]

Originally Posted by Ron in Quincy

I prefer to use original jets; inspect the tip to be sure it is not damaged. Have found over the years that Zenith and Holley single venture original carbs the main jet was a #19 and the opening was .037.
I do not solder up and re-drill jets, just the way I do, others may not agree !!!

Ron

I've only restored a few carbs for myself and I do it the same way Ron does.

[1930marie]

Thanks! Too much coffee and no sleep I guess. I soldered up a #64 and #65 - installed the 64 and what a difference! All is well - no fouled plugs! Thanks George for the wake up. It was pretty funny at the hobby shop trying to fit the 62 in the main jet. Getting old is horrible.

[1930marie]

Thanks Tom! Im using repro jets until I learn more what Im doing. My dad actually gave me a box full of original jets years ago that I classified as junk 35 yrs ago! Thank you for your information on the jets. I am a 100% original car guy and I'm noticing my breed is heading toward extinction. It's a blast and constructive time restoring 85 year old parts to perfect mint condition. It just all takes time that less people these days seem to want to invest. The Model A was not considered an antique car when I was a kid, parts were readily available. We grew up during a fabulous time in American Industry.

[1930marie]

Ron - in both carbs I restored, they had original #20 main jets. Does a #19 main jet have a smaller bore/lean than the #20?

Michael

[Mike V. Florida]

Originally Posted by 1930marie

Ron - in both carbs I restored, they had original #20 main jets. Does a #19 main jet have a smaller bore/lean than the #20?

Michael

From Oct 1927 through June 1928 they were numbered "20", which was 0.0394" diameter. From July 1928 through 1929 they were numbered "19.5", which was .0384" diameter. From 1930 through 1931 they went back to a number "20".

[johnbuckley]

If you Guys can think in millilmetres Zenith jet numbering is all much easier to understand.... 20= 1mm diameter 19=0.95 mm diameter 18=0.9 mm etc

[Dollar Bill]

"Does a #19 main jet have a smaller bore/lean than the #20?"

Post #7 - The smaller the # size, the larger the diameter!

[Dollar Bill]

Thank you Vince - I hope you don't mind that I took the liberty of quoting your jet number decoding algorithm below - Great info on your site!!

"The original Ford / Zenith carburetor jet number found stamped on the jet is the jet orifice size as expressed in 0.05 mm increments. For example, a jet marked number '18' has an orifice diameter of (18)*(0.05) = 0.9 mm = 0.035 inch."

[johnbuckley]

Originally Posted by Dollar Bill

"Does a #19 main jet have a smaller bore/lean than the #20?"

Post #7 - The smaller the # size, the larger the diameter!

Jet 19 is a smaller diameter than jet 20 because a jet number 19 is .95 mm dia and a jet numbered 20 is 1.0mm dia. To confuse things US drill bit sizes go the other way... the smaller the number the bigger the diameter.
quick guide

jet number 11, dia 0.55mm , US drill bit size between 74 and 75
jet number 18 , dia 0.9mm , US dril bit size between 64 and 65
jet number 19, dia 0.95mm , US drill bit size between 62 and 63
jet number 20, dia 1.0 mm , US dril bit size between 61 and 60