thrustnut Posted August 31, 2009 Share Posted August 31, 2009 Hey all, I have a 280Z with an L28 running an Arizona Z intake and Carter 600 CFM carb and have noticed a weird problem that I am attributing to my carb but am unsure how to fix. When taking a semi-sharp corner under throttle (never tired it more then just part throttle) my car will sputter, then when back straight, clear up and pull just fine. By semi-sharp I mean just a normal 90 deg. left or right at an intersection. The faster I am moving, the worse it is, so I am just coasting it around a corner then getting back into the throttle when out. I have a narrow band O2 I am using for basic tuning and it goes full lean when I have the problem. I have spent allot of time tunning my carb, and have it pretty dialed under all other conditions, the only other time I'm lean is on the highway at normal highway speeds with the throttle just cracked, and even then its not off scale lean like it is around corners. My Dad had a Carter on his truck and said that his would sputter when the nose of his truck was at a pretty good angle when off roading, so I'm thinking because my carb is mounted sideways, it's the same problem only opposite. I am running a Carter 5 psi electronic fuel pump (non-adjustable), so I wonder if a little more pressure to the carb would stop it...This is my first carbureted car, so the little things like this still stump me. Any ideas would be appreciated. I think I gave all pertinent info, but if you need more, let me know. Thanks Oh, and yes I did strip it down and clean it out, replaced the needles and seats, try it richer and leaner, checked float level, blew out the air tubes, car runs great other then around corners. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted August 31, 2009 Share Posted August 31, 2009 I have a similar setup on my car: edelbock 500 cfm carb (same design as the carter AFB), same manifold. I havent had any such issues with my setup but I know that due to the design of the 4 bbl manifold there may be inherent issues with mixtures going rich/lean due to g forces in cornering. This may be partly causing the problem, however, I've been autocrossing my car all summer and cant really report seeing any real problems attributed to this. If this really is the case, I dont think there is a way to deal with this problem without throwing out the manifold. Also you may be just having issues due to the design of your carb. Ive done a little research on Carter AFB style carbs, and found that the carbs can flood/starve when subjected to angles or g forces due to fuel sloshing inside the fuel bowl. What you can try is getting "off road" spring-loaded needle seats like these: http://www.amazon.com/gp/product/B00062Z2KK These are for off roading where the car is at all kinds of wierd angles, I've read these help quite a bit in their applications. I've been running these on my car, as I mentioned, dont really have issues of stumbling around corners. Quote Link to comment Share on other sites More sharing options...
jeffp Posted August 31, 2009 Share Posted August 31, 2009 I have run carter carbs on other cars and never had problems with leaning out with them. I have even run this carb on 4 wheel drive jeeps and trucks without a problem. I would recommend setting the float levels a little higher. I realize the carb is sitting 90 degrees out of its design install, but if the float levels are not high enough, then yes it can be a problem. Ever try to four wheel a holly, it doesn't go lean but it will flood the engine in a heart beat. So give the float level adjustment a try nd it should fix you up. What I use to do is to put the top cover on the engine, cycle the fuel pump and remove the cover to look at the fuel level. that will give you a good starting point. Dont worry to much about flooding as the carb uses the needle jets on the primary and it will not flood. You should be able to find a happy level that will work for you. Quote Link to comment Share on other sites More sharing options...
thrustnut Posted August 31, 2009 Author Share Posted August 31, 2009 Thanks guys, I just got off the phone with my Dad and he was telling me about the off-road kits they make for these carbs and how they fix the rich/lean condition so I'm gonna try to find a set here today or tomorrow. I think my floats are ok, but I will check them again while I'm in the carb. Again, thanks for the info and I will post my findings. Quote Link to comment Share on other sites More sharing options...
thrustnut Posted September 1, 2009 Author Share Posted September 1, 2009 Off road kit did the trick- can cut through corners now till' the back end breaks loose. Thanks for all the help...now if I could just figure out how those weird needles work! Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted September 1, 2009 Share Posted September 1, 2009 Off road kit did the trick- can cut through corners now till' the back end breaks loose. Thanks for all the help...now if I could just figure out how those weird needles work! Good to hear. I know very little about these carbs but I think what the spring loaded seats do for off roading is act as a shock absorber to keep the movements of the floats to a minimum and prevent carb flooding/starving in the rough bumps on the trails. The g forces in cornering in our application probably have a similar effect to those bumps. Does your carb happent to stall/stumble during extremely heavy braking? I'm encountering this problem at the end of an autocross run where I have to brake hard to slow down the car and enter the pits. The fuel will slosh side to side in the carb during this heavy braking flood/starve it. Its not a big deal, since it only takes a quick rev to get it back to normal. Once I get this worked out Id say my car setup will be fairly bulletproof. Quote Link to comment Share on other sites More sharing options...
thrustnut Posted September 2, 2009 Author Share Posted September 2, 2009 Yes, it actually stalled today at the stop light at the end of the freeway off ramp. It's a pretty long off ramp and has a couple nice turns on it, so I sped up and then had to lock it down pretty good when the light turned red. It stumbled a little then actually stalled (first time that's happened). It started up again without much trouble and I attributed it to the bigger cam and low idle. It has tried to stall a few times around town, also when stopping, but a little blurp seems to clear it out. Let me know if you find something, for me its a little annoying (I don't race, so not that big a deal) for you it may be a little more important. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted September 2, 2009 Share Posted September 2, 2009 Dang, I was hoping I was the only one with such issues. Oh well, at least that means I'm not doing anything wrong. However, my car doesnt really ever stall out under regular street braking conditions. There could be a second issue at work here. For me, it really only happens in panic brake type situations (clutch in, slam brakes hard). I did some searching a few months ago on off road forums and found this page: http://www.ih8mud.com/tech/carter.php Off that page I have done the first two things (off road needle seats, lowering float bowls to between 5/16" and 3/8"), though it seemed to help a little, the problem still persists. I havent tried the third trick yet (squishing a rubber hose in the balance tube thing). If you like, give it a whirl and let me know how it goes. Quote Link to comment Share on other sites More sharing options...
thrustnut Posted September 2, 2009 Author Share Posted September 2, 2009 This wasn't what I would consider regular breaking, this was about as hard as I have slowed from 50ish to stopped and I couldn't roll off the brakes in time to tap the gas. I have a question about the float level adjustment, this will change your fuel setting across the board so I'm assuming you tune to compensate? I may try the last, though I don't know about putting foren objects in my carb. I can see the purpose of what he is doing, and it may keep fuel out of the forward bowl under hard breaking. Like I said before, I think mine might have more to do with the low vacuum in my engine, then working the brakes hard steeling more air, stalling the engine. I might just bump my idle up a tiny bit and try it again. I might have some vacuum line in my drawer, if so I will try it out on the way to work today and let you know what happens. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted September 9, 2009 Share Posted September 9, 2009 I know its been a while but have you had a chance to give that a shot? I am very interested to hear if it works or not... Quote Link to comment Share on other sites More sharing options...
thrustnut Posted September 9, 2009 Author Share Posted September 9, 2009 Hey, sorry only taken it out the one time since putting in the off-road kit. I work nights and it's been in the low 40's on the way home which is no fun without a heater, and the temp swings ( 80's in the day and 30-40's at night) make tuning a carb a pain in the butt. I would also like to figure somthing else out...there's just somthing weird about putting FOD in my carb and driving it. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted September 9, 2009 Share Posted September 9, 2009 Yes, that is part of the reason I have been putting off fixing that issue as well. Just something unsettling about putting random stuff into the carb. I dont think it would cause any real harm in those passages though since it doesnt actually mess with any of the air circuits in the carb. I will try it one of these days, and will post if I find anything out... if you get to doing it first, let me know too. Quote Link to comment Share on other sites More sharing options...
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