mjr46

oops one error made when you go to b/g website click on products and scroll to bottom of page and to the left click on selection guide. hope that helps

mjr46

By the way what does the car run in the 1/4??? time?? mph??? all motor and with nitrous just curious cause I want to add a nos kit to mine 100 shot and wondering how much improvement it'll be???

capri_83

46 It runs 13.4's (hankook 275/40R17) street tires.....I have M/T ET street slicks....have not run them with this new combo.......last year(stock motor)motor was 13.5's with slicks and 12.9's 100 shot......wife made me take out bottle ti'll motor is broke in and dailed in....

67mustang302

Well, the carb is prolly a bit on the large size if it's a street car, even with nitrous, remember nitrous is giving you the oxygen, not the air coming through the carb. Though the better pumping you get when you spray will make a 670 work well, but smaller would give better n/a mileage and throttle response on the street. As far as your problem, I'll bet it's the accelerator pump circuit. If it's going lean then there's several things you need to check. Make sure that when the throttle starts to open the pump is squirting, and I mean ANY movement of the throttle and the pump should be moving fuel, even if only slightly. Try changing cam position and making sure there's no slack in the spring loaded arm that moves the pump arm. You may need a differet pump cam/squirter setup as well. I'm running the 570cfm on my 302 and it took quite a bit of tuning(almost a month) to get the accelerator pump to where it works right. I had to make several squirter size and cam changes. Make sure that the arm that rests on the cam(the one with the spring) is setting properly on the cam, so that as soon as you start moving the throttle it's working the pump. It sounds like you either have some slack in the pump circuit and it's not activating the pump, or the spring is too soft. And about that spring, by loosening the nut on that spring loaded arm you do several things to the pump. One is that it causes the pump to sit partially depressed at idle limiting the amount of fuel it can draw in, and thus the total amount you can deliver. The other thing that loosening that does, is causes the spring to compress and absorb tension when you give it some throttle, especially light throttle. If the spring is too soft, when you give it a bit of part throttle it'll move the arm, but rather than depressing the pump right away, the spring will compress and fail to cause proper fuel delivery, and then the pump will slowly deliver fuel as the spring expands. You might want to try by making that spring as tight as you can without having any slack or floppiness between the spring loaded arm an the pump arm, preload the spring. Also, if you have taken the carb apart to change jets/power valves, remember to pull the fuel bowl and metering block UPWARDS as you tighten the bolts. The metering block and bowl can sit higher or lower, if you set it lower then it puts the pump arm farther from the cam arm(the one with the spring) and causes you to have to loosen the spring to get the arms to contact without slack, and that will cause low spring tension and the condition I described abhove, not enough spring preload. So when you deal with the pump, first make sure the bowl/metering block are sitting as high as they can when you bolt it up. Then make sure that there's not any slack in the 2 arms, and that ANY amount of throttle from off idle, no matter how small, starts the pump delivering fuel. Then you can work with squirter sizes and pump cams to fine tune it. You can also use the spring to tune it as well, by tightening/loosening the nut you can change the amount of preload on the spring, which will change how the pump reacts. Tighter spring= quicker/more pump response, loosen the spring and you can soften the pump response(very useful for VERY fine tuning, ie when you have enough total pump delivery but need slightly less/more pump and part throttle off idle).

capri_83

67 I have tried the adjustment on the spring set at spec. and one turn tight and one turn loose.......and it is set so that even looking at the throttle it pee's fuel......that was the first thing I checked......thanks now Holley said not to go too far past spec setting or you may rip acc. pump gasket is this a concern if I go two turns stiffer....pump cams I have not tried...... and do not know how to set or select them....I do not have spec. sheet for carb at work with me...and the carb is a bit big for the motor but.......next year see's new heads....and I wanted to be ready......this is the carb HOLLEY told me to run...........and now they are lost on how to fix this issue.....the nice part is...that on a tank of fuel I get about 480km (bout 300mile)way better than old carb.....

67mustang302

I've been all over the place with my spring and haven't had any problems. You need to get the pump cam assortment, but do NOT use the 50cc pump cams on the 30cc pump, you'll damage it for sure. Also changing the position of the cam makes a huge difference as well. The #2 slot gives you the full duration of the cam(ie delivers more fuel) and the top hole places the cam slightly rotated into the duration of the cam at idle, so it delivers less fuel because it travels a bit less duration. If it's too lean it needs more fuel from either larger squirters or more cam. What does it do as you roll into the throttle? What does it do when you snap the throttle as quickly as you can, what does it do when you do that at different rpm ranges? What does it do at light part throttle off idle, heavy part throttle and nailing it? Those all tell you where to fix the problem. If it suddenly dies out and stumbles hard then comes on like a rocket it's dry on fuel, if it has a bog but accelerates and then pulls harder it's prolly too wet on fuel, and if it goes "burble burble" when you nail it, andgoes no where,it's drowning.

capri_83

Ok slow down!!!!!! 2000 or under RPM very light opening of throttle stumbles.....let off ok.....nail it ok(very ok)......only under 2000RPM.......any gear.....flat roads...........hills.......... does not seem to matter.... goes lean.....as the power valve kicks in goes rich and stumble gone......

67mustang302

Sounds like the initial shot from the pump is on the thin side, try more preload on the spring, or possibly a cam with a faster ramp. What color cam do you have now? It's delivering enough fuel overall, but just not enough at a little bit of part throttle

capri_83

stock one is red and yes just off idle it's bad.......everywhere eles it just fine.......I was going to see if cam has another hole and try that......but boss told me some customers want there cars back.....JERKS......LOL....I check after work and let you know thanks for the help

67mustang302

The red cam isn't a large delivery cam, but has a bit of a slow initial ramp, try changing the position and see if that helps...if it's in position 2 then you're getting the start of fuel delivery with a soft ramp rate, slot 1 will deliver less overall fuel, but it'll start past the soft ramp and give you better response. If it gets worse that way when you crack the throttle all the way, then you'll need to try a bigger cam, like the orange one, possibly different squirters, though the 31's you have should be plenty big