Forces Posted February 9, 2007 Share Posted February 9, 2007 I hooked a wide-band up and adjusted my AFR to about 14.6 at idle, advanced the timing to 14 degrees, and under part throttle it ran way rich, about 11.1 If I stab the throttle, it gets as rich as 10.7. I'm running a 750 CFM carb, my acceerator pump is on the lowest setting. I am thinking that maybe it's too much carb for the engine (383 stroker.)???? When I get on it at higher RPMs, it runs okay for a while, and then the exhaust starts popping like crazy, but I think that is the glass packs. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted February 9, 2007 Share Posted February 9, 2007 Do you have a big cam in the motor? Sounds similar to my problem with my L28 (camed/minor head work) with SU carbs.. Too much carb/fuel for low throttle (don't need a A/F guage when you can smell that much fuel in the exhast!), it's just right in the mid range, and falls off (goes lean) up top... is that carb a vac secondary or mechanical? Could be opening up too soon which richens it too much? Also.. that sounds like a lot of advance for a 383.. shouldn't it be back around 10-12*? Quote Link to comment Share on other sites More sharing options...
Alf Posted February 9, 2007 Share Posted February 9, 2007 A 750 cfm carburetor should not be too big, I've ran 750s on 305s for a short while with no problems. Remember, the cfm rating is cubic feet per minute, so a bigger rated carb will not necessarilly give you more fuel. Usually the throttle bores are bigger to allow for more air to enter the engine. If you're running a Holley I would check the power valve, it may be blown and would cause the engine to run rich at all times except when under full throttle. You said you set the timing to 14 degrees which should be alright. What is your total timing? Are you running vacuum advance? When do you get full mechanical advance? What kind of vacuum is the engine pulling? The popping may either be too much advance, or just a leak in your exhaust at some point. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 9, 2007 Author Share Posted February 9, 2007 I'm not running a Holley, it's a manual choke Edlebrock. The vacuum is about 18 inches/Hg if I remember right, and it doesn't fluctuate at all (no vacuum leak). And yes it is a vacuum advance dist. The AFR screws are almost bottomed out on the lean side (twisted about 1/2 turn out) , and that is to achieve 14.6 at idle, which is about 1000 rpm. Quote Link to comment Share on other sites More sharing options...
Paz8 Posted February 9, 2007 Share Posted February 9, 2007 I am running a 750 Holley on my 350 and it works well with 3.54 rear gears and 700r4 trans, good snappy throttle response. I ended up going one jet size lower in the primary and left the sec. alone. Is the carb new or used ? Someone may have set it up way too rich, if it's new it should be close to being correct right out of the box. Use a vac gauge to set up the idle mixture, set for highest vac reading then go a hair rich with the screws. Spark plug heat range also plays into carb tunning, it takes some trial and error to get everything worked out, better too rich than too lean. Quote Link to comment Share on other sites More sharing options...
naviathan Posted February 9, 2007 Share Posted February 9, 2007 That was going to be my suggestion was changing to a smaller jet. If you're good at idle you may want to look at your secondary. Don't the Edlebrock carbs have seperate adjustment screws for both primaries and secondaries? Quote Link to comment Share on other sites More sharing options...
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