Does anyone know the correct drill bits to drill out holley jets for # 102 thru 110. I have a chart but it does not match a fraction size drill bits or number or letter size drill bits.I am testing a E_-85 carb thursday and need the bigger jets

JET Size
101 0.126 (1/8 .125, 3.20mm .126)
102 0.128 (#30 .1285)
103 0.130 (3.30mm .1299)
104 0.134 (3.40mm .1339)
105 0.137 (3.50mm .1378)
106 0.141 (#28 .1405, 9/64 .1406)
107 0.145 (#27 .144, 3.70mm .1457)
108 0.147 (#26 .147)
109 0.150 (#25 .1495, 3.80mm .1496)
110 0.156 (5/32 .1562)

remember you want 27% more volume NOT a 27% bigger hole.

Thanks for the chart , but if you have a 105 jet dont you need to drill a .137 hole , there is my question ,what size drill bit is a .137 , a fraction bit , number bit , or a letter bit ?

#29 is .136 3.5mm is .138

Thanks for the info. So holley made this with special drill sizes , I will just have to find something close to the size as per you example.

I think he is looking to convert the decimal into a fraction .128 is 128/1000 which in its lowest terms is 16/25 but at the same time.... .126 is 63/500

no , what I am trying to figure out is what drill bit sizes to use to make the 101 thru 110 jets using smaller jets.

Well combined with the previous post above I think we accomplished that Jimmy... even though the sizes seem unorthodox.


JET Size......drill bit size
101 0.126....63/500
102 0.128...16/125
103 0.130...13/100
104 0.134...67/500
105 0.137...137/1000
106 0.141...141/1000
107 0.145....29/200
108 0.147....147/1000
109 0.150.....3/20
110 0.156......39/250

Have you changed anything else on the carb besides
going bigger on the jets... not quite that simple

Raff....you will know better than me I think, but should he be looking more at reamers than drill bits???

I was searchin in the special deal section and cant find a thing......


I know you can get reamers in the crazy sizes

yes the carb has been changed to E-85 by Heath Daniels @ race on E-85. Just trying to have spare parts to change jets if needed & 100 - 110 jets are not in stock at most speed shops and @ $7.00 a set of 2 , thought I might be able to fix the jets myself with drill bits.

You can get "close" with drilling out jets. But unless they are flowed, you can be a couple "sizes" off in flow. The length of the hole and the chamfer (bevel) and both the entrance and the exit will change the flow of the jet.

IMO, at those large sizes, drilling is OK for getting it close, but then you will need flowed jets to fine tune it.

Thanks for the help, weather (rain) killed testing tonight , try again next week. Looking forward to trying this e-85 fuel. Got to figure it out before the Mopar Bristol Race Labor Day.