Off the line bog

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smythge

65 with a BIG BLOCK
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Just got everything done in the conversion of a 318 to a 440 in my 65 Dart. The motor is a stock 440 with about 60,000 miles on it. Has an Edelbrock performer intake, new edelbrock performer 750 carb (factory settings still) New mopar performance electronic ignition with the orange box. New mechanical fuel pump, New plugs & wires etc. good compresion in all 8 cylinders.

My problem was a flat spot at about 3500 rpm I checked the timing and advanced to intial setting of 12-14 which seems to have helped the flat spot. Also the vacuum advance is hooked up the ported line on the carb.

My main problem now is when I mash the gas from a dead stand still it bogs, sometimes dies, other time backfires through the carb and then takes off if I feather it is fine. I know this can either be a carb related problem or timing. What I am wondering is if it is a carb related problem is it too much fuel or too little fuel? The accelerator pump is currently set in the middle of the 3 settings, floats are set (I checked those) it doesn't smell at all rich at idle and I have the air fuel mixture screws equally adjusted for maxium vacuum which is about 19 at idle. Does not blow any black smoke and there are no vacuum leaks. I should also mention it is only 20 degrees outside. Give me your suggestions on where to start, also I know a carb tuning kit with different jets, metering rods and springs are in my near future.
 
Usually a backfire through the carb is a lean condition. I would go 2-3 steps richer on jets/metering rods, but the fact that it is cold could be part of the cause.
 
Put your vacuum guage back on and set your timing to get maximum vacuum, then maybe back it off a degree or two and try it there. The fact that a timing change helped the 3500 RPM flat spot indicates it may need even more advance that what you currently have. I've used the old Carter AFB carbs for years and just love the way they run on a street engine. However, you usually need to dial them in for your particular combo. As 66dartman said, it sounds like it is running lean so go the 2 or 3 steps larger on the jets and rods. Also, before changing the jets and rods, try setting your accelerator pump for maximum pump shot. Good luck.
 
I'd start with more accelerator pump shot. I've only dealt with holleys, but it sounds like you're not getting enought initial fuel when you mash the throttle. More accelerator pump shot should help.
 
If it's an MP distributor, and more initial timign helped, then I would check your total timing. Do you have adial back timing light? If not, get a timing tape and apply it to your balancer. ($5 maybe?) It will allow you to see exactly when and how far the timing gets moved by the advance. My guess is, it is too slow, and too much total. That would eb about right for an out of the box piece. Thet total can be limited by using the allen set screws down below the advance plate. but you need to be able to tell where it is, to get it in the right spot..unless you do trial and error. Get the timing setup right, then move on to the carb. Timing affects carb, carb doesnt affect timing. You may find after the timingis set up that the carb needs tweaking..They are generally lean, and the springs under the power pistons are more than likely wrong for your vaccum level. That's why it's popping.
 
Yea, I'd agree with Moper. I had the same problem with my 383 and after finding the ignition was just fine I replaced the vacuum secondary (single accel. pump) 4 barrel with a double pumper. Goes like hell now from the second you mash her. :evil2:
 
While I've never messed with Edelbrock or Carter carbs, the same basic tuning tips apply.

DO NOT jet up for an off-the-line bog That will be a band-aid fix and can cause you to run rich overall. If the bog is fuel related, work on the accellerator pump circuit. Basically, accellerator pump circuit for off-the-line/60' times, jetting for cruising/mph.
 
Ok need some more suggestions. Still having off the line bogs & around 3500 the motor seems to miss. The timing is set at 12 intial 36 total. I did move the accelerator pump arm to the middle and lower hole and that made it much worse so I moved back to the top. Checked all the plugs and wires no problems there. Idles & runs great cruising and above 3500 rpm but under mild acceleration and off line it stumbles, going to try a different coil tomorrow, but am begining to think it's this carburetor. Please post any suggestions you have.
 
wel, the timing is where it should like it..so carb is next. The Edelbrocks are lean out of the box for a lot of cars. The fact that it got worse as you leaned out the accel pump by using the outer holes. You sould get the tuning guide, and the strip tuning kit for the carb. You can change the rods, or the jets, and alter cruise, power, and light throttle mixtures. A smaller diameter rod in any step will be richer in the same jet. Also, any cam will change what you need for power pistons springs your car. The charts for the jets/rods and power piston springs is in the tuning guide. What seperates the "good" from the "great" is tuning. Take your time. MAKE ONE CHANGE AT A TIME. test drive in the same way/place each time. The final setting you may want to installa fresh set of plugs..They are easier to read, and as you get closer to the perfect setup, the old plugs might be stained and hard to read.
 
I think moper has got it , if this was a holley i would say , power valve, i think the piston springs do the same basic thing....
 
I was driving the car tonight, and started it with the manual choke on, and forgot to turn it off, I had a ton of power and no 3500 RPM stumble. I also pulled a couple plugs and have a light tan color, I am guessing that this means a lean condition, any suggestions?
 
Definitely sounds lean. I would agree with moper's advice and game plan from his reply on 3/19. Good luck and keep us posted on your progress.
 
yes..start tuning the carb. Light tan is what you want..no color at all is lean, black is rich. if you ran with the choke on, and it got better....IT'S LEAN WITH THE CHOKE OFF!!!! so you need to richen the jet or rod, or both.
 
Talked to a couple old time mopar experts and they suggested I may have a warn cam or my hydraulic lifters may not be pumping up causing the 3500 RPM stumble. I have messed with the timing and carb and can't seem to correct the problem. It feels like it's missing at 3500 RPM then again at higher rpms and falls flat on its face going from a stop to WOT. I plan on doing a compression test this weekend, but want some experts opinions on what else to be looking for.
 
Dump that eddy carb......my 318 was doing the same thing. I could have bought two Holleys for all the money I spent on tuning kits with metering rods and jets for that POS edelbrock carb. I put the vacuum secondary Holley on there and haven't looked back.
 
Lifters dont "pump up". They are either working and maintaining 0 lash, or they arent. Bleeding down is when the rpms and valve springs collapse the hyd part of the lifter against the oil pressure..Thus the engine loses power..That's valve float. Variable duration lifters will "pump up" when the rpm raises off idle. They are designed to make large cams more drivable and idle better. But std lifters dont. It's not a lifter problem. You've already found the problem.
 
If it improves with the choke on...yes it is lean big time. Moper is right, tune the carb. Not a lifter problem. Bad hyd. lifters are noisey. Almost will sound like a solid but louder. Please advise as to what you find works. We ALL are still learning...Good luck, Terry.
 
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