TrunkMatt Posted December 5, 2011 Share Posted December 5, 2011 Holley 670 Ultra Street Avenger (single pumper) w/ Vacuum Secondaries. I am now at 76 Jets for my primaries & the spark plug color looks good. I was getting some carb backfire at 72 / leaning out. So, now that my primaries are good, what do you all should my secondaries be in relation?? I cant find much info on this... everything online speaks to primaries only & I don't have any holes cut in the collectors (yet) for installing an O2 Sensor (maybe next year)... so I can't take a reading electronically. I currently am running 78's on the secondaries, and it seems to be fine - plenty of pull when they open up. Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted December 11, 2011 Share Posted December 11, 2011 What is the list number of the carb? Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 11, 2011 Author Share Posted December 11, 2011 List number - as in SKU / Item number? 0-86670bk Now I have it staggered at 76 Primary, 79 Secondary now (on a 383). Quote Link to comment Share on other sites More sharing options...
John Burns Posted December 11, 2011 Share Posted December 11, 2011 I would, starting from whatever the stock sizes were, increase the secondary jets the same number of sizes you increased the primaries. Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted December 11, 2011 Share Posted December 11, 2011 I usually like to go up jet sizes equally. I would back the fronts to 74 and bring the secondary to 80 and see where that gets you. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted December 11, 2011 Share Posted December 11, 2011 what Mike said, always adjust both ends the same, if you move the front 2 steps move the rear 2 steps. You should also adjust at least 2 steps at a time, single steps changes are not enough to make a readable difference. If you want to be able to dial it in through the different speed ranges consider something like this.... http://www.summitracing.com/parts/AVM-30-4100/ Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 12, 2011 Author Share Posted December 12, 2011 Yeah... I am thinking I need a Wideband guage to really get this dialed in right. Been looking at Innovate's LC-1: http://www.amazon.com/Innovate-Motorspor...3403&sr=8-2 I think I'll bite the bullet and grab one. Merry Christmas to me... Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted December 12, 2011 Share Posted December 12, 2011 Innovate is a good piece.... Quote Link to comment Share on other sites More sharing options...
Ian Posted December 12, 2011 Share Posted December 12, 2011 Yeah... I am thinking I need a Wideband guage to really get this dialed in right. Been looking at Innovate's LC-1: http://www.amazon.com/Innovate-Motorspor...3403&sr=8-2 I think I'll bite the bullet and grab one. Merry Christmas to me... That is the one I have but with a different gauge, and love it! That is a good price too! Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 15, 2011 Author Share Posted December 15, 2011 The LC-1 arrived today... now I just need to get my bung welded (that sounds dirty). Quote Link to comment Share on other sites More sharing options...
Canuck Posted December 15, 2011 Share Posted December 15, 2011 now I just need to get my bung welded Quote Link to comment Share on other sites More sharing options...
Andy's Auto Posted December 15, 2011 Share Posted December 15, 2011 The LC-1 arrived today... now I just need to get my bung welded (that sounds dirty). Awesome. I have the LC1 on my 81 Malibu and besides a chassis dyno with 4 gas, it is the single best tuning tool you can get. Quote Link to comment Share on other sites More sharing options...
wallaby Posted December 16, 2011 Share Posted December 16, 2011 Andy: (not trying to hijack the thread, this may help Trunkmat as well) I have the LC1 also; it is great at displaying the numbers, but there is little info on what the numbers should be. When we are jetting the carb, what is the target for cruise mixture, and the target for WOT mixture? I imagine there is a different target for idle mixture too? Do the numbers vary from engine to engine? I'm just looking for general guidelines so I can dial it in as best as possible. Quote Link to comment Share on other sites More sharing options...
Andy's Auto Posted December 16, 2011 Share Posted December 16, 2011 Andy: (not trying to hijack the thread, this may help Trunkmat as well) I have the LC1 also; it is great at displaying the numbers, but there is little info on what the numbers should be. When we are jetting the carb, what is the target for cruise mixture, and the target for WOT mixture? I imagine there is a different target for idle mixture too? Do the numbers vary from engine to engine? I'm just looking for general guidelines so I can dial it in as best as possible. At idle, it will usually bounce all over the board from say 13.0 to 17.0. Not easy to get a good reading with low exhaust flow. Idealy the best way to set idle is with a true 4 gas and base it off of HC PPM and your CO readings. For best driveability, just shoot for 14.0 to 14.9 at cruise as 14.7 is ideal. At WOT, I adjust for 12.6-12.90. A little rich might cost a few ponies but leaning out anything is bad. Because you know that sooner or later that switch that says "NITROUS" is getting turned on eventually. lol. At the track I just aim my GoPro camera at the gauge as it gets pretty busy during a 9 secong run. After the run I upload to my craptop and see where it is at based on audio and the tach is right next to it. More than anything it tells you wich way to go based on weather conditions. Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 20, 2011 Author Share Posted December 20, 2011 I got the sensor and gauge all wired up today & calibrated it in open-air per instructions. The bung gets welded in tomorrow. Wasn't too terrible to install... have to do quite a bit of clean-up of the wiring under the dash - but she is working, and that is what matters. Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 21, 2011 Author Share Posted December 21, 2011 Got the bung all welded in today. The guy that did it was the same one that ran my new exhaust... so he did it for free (that and it is my birthday). Guage works like a champ. I am indeed going rich (reading of 10.5) at low rpm... I am thinking either the secondaries are opening too soon or the power-valve is a bit premature. Quote Link to comment Share on other sites More sharing options...
Andy's Auto Posted December 21, 2011 Share Posted December 21, 2011 Matt, at cruise shoot for something around 15-16 with jetting. Cruising a little on the lean side keeps the plugs clean and you can make it up with secondary jetting. As long as it doesn't surge you will be fine. What power valve are you running now? What is your idle vacuum at? Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted December 22, 2011 Author Share Posted December 22, 2011 My Power Valve is a 6.5 --- Vacuum is about 8 HG at idle (in gear / automatic) I am thinking I should go 4.5 for the PV. Quote Link to comment Share on other sites More sharing options...
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