blow thru carb jet selection?
05-20-2011, 12:13 PM
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blow thru carb jet selection? Fixing to start tuning my blow thru ls1, just curious what a good jet front and rear would be a good start for 5-8psi. Its a 650 double pumper carb, I have 72's in the front and 81's in the rear for now. It seems to rev good. But its way rich on the idle side. Any tips? I'm running the a1000 fuel pump, aeromotive frp, set @ 7-7.5psi idle. What kind of fuel pressure you guys running?
05-23-2011, 08:27 PM
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I am running 6.5 lbs of fuel pressure. Is your regulator a boost reference style? Changing jets will not affect the richness at idle. U have to adjust that with your air screws. I dont remember my exact jet combo but I think my fronts are somewhere around 80 and my rear is around 90. My carb is a 750 and I am running 7 lbs of boost. Hope this helps. Easiest way to tune the carb and get it right is to invest in a wideband. Good luck
05-23-2011, 08:39 PM
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Ya I can't seem to get the carb to lean out with my air screws. I do have a wideband, but its decided to screw up so I gotta get another one. My regulator is a boost reference regulator also. Thanks for the tip. It helps as a start.
05-23-2011, 08:59 PM
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I had that problem also.Turning the fuel pressure down a lb will help alot. Double check your float levels also. what timing your running at idle? More timing will clean up the smell some. Mine idles around 13.5 to 1 af. I found if I went much leaner it had a very small stumble taking off slowly but of course every setup is diferant. Wish I could give u the exact jet sizes but I dont remember. But these should get u close. I am close to sea level so keep that in mind if your at higher elevation u will need smaller jets.
05-23-2011, 09:15 PM
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Thanks, I'm about 300 above sea level, it seems to of run best with the 78 jets in front. I will turn down the fuel pressure some n see what that does. As for timing, not sure yet. I've got the eldebrock version (they screw you on) I've gotta buy the msd version to start tuning. What kind of timing you running?
05-25-2011, 08:59 PM
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38 while cruising then under boost it ramps down to 18 at 5000. i have ran as much as 21 at 5000 with no detenation but backed it off to 18 for around town. thats on 93 pump gas with 10.2 to 1 comp ratio and 7 lbs max boost
05-26-2011, 06:25 AM
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Sounds good man I'm also on 93 pump gas. I'm gonna order my msd box next week so I can start getting a good street tune on it.
Have you used the 2step control on the msd 6010 box?
Have you used the 2step control on the msd 6010 box?
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07-21-2011, 06:40 AM
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Got on the dyno last week and was doing my warm up just part throttle cruisen and noticed my headers getting cherry red, I didn't look @ the a/f it slipped my mind @ the time. But I think its lean @ part throttle. How do you richen it up without changing anything else? My tune is dead on other than part throttle.
