It covers decimal, fractions, numbered drill bits, letter drill sizes, metric drill bits, and probably a few more things I forgot to mention.įor more on twist drills in general, see our twist drill article for all the different types and tips for holemaking with them. I'd rather have a few extra MPG and be able to "set-it-and-forget-it".It’s very convenient to have a drill chart around with bit sizes, so we thought we’d put one here for you. It would be quicker, faster and more tune-able with a 750 double pumper but I'm not drag racing. I have a feeling it's designed to have a lot of "crossover" between the idle and primary circuits to give that excellent response. Not sure what exactly is going on there but I'm not going to lose sleep over it, also not going to spend any money on another carb, that's going to go towards a full MPFI conversion.Įven the owner's manual that comes with the carb says to target a 13.5:1 mixture at cruise using a wideband, seems pretty rich but that's what they say. Haven't checked my spark plugs but I'm not too worried about it, others have said their plugs looked fine even though their O2 sensor showed it was rich. However it always seems to be "I don't like the numbers my AFR gauge is showing but it runs fantastic" so I'm just gonna roll with it. Seems like the rich off-idle cruise is just the way these carbs work, lots of people complain about that online. Once you remove materiel it's near impossible to put it back. The moral of the story is drilling jets is a bad idea. All that junk went in the shitter and I order Kinsler nozzles and jets. The pills I was using that should have been leaner were in fact, flowing LESS than they should have because the company that made them had ZERO standards. I ran down there after work and I watched him flow all 20 of my pills. So I called a buddy and he hooked me up with a local guy who had a flow bench for fuel injection. If I was so stupid I couldn't pull fuel out and my tuning was slowing the car, I should pack it in. And the plugs looked like the engine was a bit more fat. 010 (on mechanical injection the jet, or pill is in the return line so a bigger jet is LEANER which is opposite of a carb but the principal is the same) and the car went slower. I was at the track and it was hot Hot HOT and the DA was so high the birds were wearing oxygen masks. I was buying jets and nozzles that were said to be flowed. In the late 1980's I was working with mechanical FI and alcohol. If you drill out that out, you can have a jet with a bigger hole that flows LESS and you will go wild trying to sort it out. Just use a good lube.Īgain, you also need to account for the radius at the entrance and exit of a jet. Brass is grabby **** and you can stick a reamer, although that small a reamer with that short length of engagement should be doable. Primaries are specific to the Street Demon only. I have other primary jets from the tuning kit which I will never use (far too small, like #76-80), is it possible to carefully drill them out and not mess them up? I've heard just using a normal drill bit will leave burrs on the inside surface which can screw up the fuel flow? I would just buy the correct jet if I could but they aren't available and I have at least 2 spare pairs of jets to mess with.īasically is there a special drill bit that can drill out carb jets properly?ĮDIT: And no regular Holley or Edelbrock jets won't interchange, only the secondaries use regular Holley jets. The primary jets jump from a #82 up to #87 and after lots of messing around with both sizes and all of my metering rods (which are basically all the ones they make, got the full kit) I could really use a #85 jet. I have a tuning issue with my 750 Street Demon where the tuning range I need can't really be had with the primary jets and metering rods available from Holley.
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