Carb Selection/advice

[a6t9vette]

Well if you guys recall I was/still am having a prob with a hesitation when I put my foot the floor (383, pretty much stock, MP Elec Ignition, Exhaust manifolds, Edelbrock DP4B intake, Edelbrock Performer 1406 (600cfm) carb.....) I have tried several differnt carb settings and mods per Edelbrock tech, springs, needles, Acc pump nozzles...) and cant seem to shake it, or really make an improvement. If im reading my plugs right (see previous post) im still a little lean and now Edelbrock has me second guessing myself and that the 600cfm carb might not be enough.
My thoughts were that since the car runs fine after the initial hesitation (when i plant my foot) that it has nothing to do with cfm since the car hasnt even gotten the chance to need that much more cfm yet when I first put my foot down, and they are now saying I should think about putting a different carb (not sure if thats a sales pitch).
So now im looking at the 1407 (750cfm) but hate to spend the money to buy one just to see if thats the prob. Since its going to take me all of 10 min once I get it to figure out if it works or not.
What are you guys with 383s running on your engines? Im running a stock (unsilenced air cleaner), and a stock hood so I have some clearances to worry about.

Thanks

 

[droptop]

I wonder if a tighter spring on the butterfly's for the secondaries would help. Boog usually means a lean condition. I have this same carb on my '75 400. It works great.

 

[6R9Runner]

It sounds like a lean condition. I'm running a 1407 2945 that was jetted for a 455 so there's plenty of fuel. As a result, my (stock?) 383 idles around 1000 rpm, kinda racy but otherwise has lots of power. I tried turning in the idle screws and it caused a hesitation similar to what you describe, but with a 4-speed I can just rev a bit more so I have left it alone. We're probably on opposite ends of the same issue, since I am considering going leaner. This might be a good time for me to see what size rods/ jets are in it and that might help us both. What is your idle advance? Taking a simple approach, does more or less vacuum advance help?

 

[a6t9vette]

If I rememeber correctly Im running around 13 degrees initial, and 37 total timing. I havent changed jets, but have tried the following rods: Stock 1459 (075 x 047), 1455 (073 x 042), and 1449 (070 x 037), various springs with each, and 0.031 nozzles (stock), 0.033, and 0.043... seems that I get a studder during the hesitation with the 1449s, other then that I didnt notice much change with any combo.....

 

[moparchris]

First off the tech line at Edelbrock is full of $%*t. Carb size has nothing to do with a stumble, unless its a holley dominator on a stock motor or something along those lines. Edelbrock carbs have a lot to be desired. It seems if you get one that works properly from the get go, keep it. If it has issues throw it in the trash and try another. Of course you could buy another Edelbrock and roll the dice. I guess that would be okay, however if you have that kind of money to throw around then you should just go fuel injection. Okay rant over, I would recommend a Holley 750 cfm. Vacuum for a stock motor with an auto trans and stock converter. If it has a loose stall or has a big cam or is a 4 speed then I would recommend the Double Pumper. I have had tremendous success with both of these carbs and 383s love the size. Back when the carbs were built by Carter, and even Weber early on, they were great carbs, not for the most HP or driveability but reliability. Holleys have come a long way in the past ten years and have proven over and again to be far superior in adjustability and HP. Any aspect of the fuel pump squirter can be adjusted not to mention jetting or even power valves to keep the idle circuit lean for better idle control. Now with superior machining techniques and better gasket technology the Holleys are proven to be very reliable. List numbers are the way to research your Holley. 3310 is the Vacuum secondary carb you need. The 4779 is the DP you need with a dash number to suit the specific options, i.e. a 4779-0 is a four corner idle air bleed control. I would recommend the four corner idle mixture control for a superior idle and restart. Good luck.

 

[a6t9vette]

Thanks for the Holley advice. I was under the impression though that the Stock air cleaner base (non Air Grabber) hits the bowls on the Holley which is one of the reasons why I have avoided it. Any idea if thats the case? Also was trying to stay away from a dual feed (like the Holley) since id have to go away from the stock apearing hard fuel lines that I have going to the Edelbrock.....

 

[Hoosier Bird]

Holley 850 DP with 4 corner idle adjusters.......improved my performance by far.........now when I grab 2nd hard I have to let off to keep it on the road.......scares my buddies to death....LOL I need to do a video and post it. I really don't want it to hook up or I'll start breaking things.....sure is fun to drive. Absolutely no hesitation. I had to put the 50cc pump on the primarys, 74 jet on primary, 76 on secondary. Green cam on secondary and the big black cam for 50cc only on the primarys. Can't remember on the squirters but if anyone needs that I'll get it. :yesnod:

 

[moparchris]

Thanks for the Holley advice. I was under the impression though that the Stock air cleaner base (non Air Grabber) hits the bowls on the Holley which is one of the reasons why I have avoided it. Any idea if thats the case? Also was trying to stay away from a dual feed (like the Holley) since id have to go away from the stock apearing hard fuel lines that I have going to the Edelbrock.....

No, they clear no problem. I cant comment on air grabber stuff though.

 

[6R9Runner]

Well, I managed to fix my problem, it might not help you but sometimes the problem lies elsewhere. My throttle cable was too tight, causing the primaries to be partially open all the time. I had tried adjusting the idle mix screws in, and the stumble resulted from a too-lean idle mixture. Idle rpm now has full adjustability, right now its a mellow 650. I have the 750cfm 1407.

No doubt these guys know their Holley's, I had a 4160 750cfm DP on a bigger cam 383 4-spd a few years ago and there was a stumble as well, which was corrected by a bigger squirter, very easy to change. You can't argue with success. Did you try a different pump setting on the Edelbrock (on the driver side, with the 3 position arm?). Just a guess, but it sounds like you're tired of guessing and leaning towards the Holley. Good luck.

 

[a6t9vette]

I have tried all three settings on the accelerator pump with no noticeable change either way. Id really like to stay away from the Holley from the one stand point that I dont think be able to get it to look the way I want with the fuel lines, on the double feel models my hardlines wont work, and on the single feed I belive its on the front driver side so same goes for the fuel lines. Would be nice if Edelbrock had test units, Id love to through a 1407 on there and just see what happens, Im just hesitant to drop the coin to test it and then find out after the $ that I still have the same prob.....

 

[SomeCarGuy]

Stay away from the 1407 or 1411.

Try a new accel pump, sounds like yours is weak. Maybe a vaccum leak someplace. Do you have the vac advance hooked up to manifold or ported?

Fuel filter new?

 

[moparchris]

I have tried all three settings on the accelerator pump with no noticeable change either way. Id really like to stay away from the Holley from the one stand point that I dont think be able to get it to look the way I want with the fuel lines, on the double feel models my hardlines wont work, and on the single feed I belive its on the front driver side so same goes for the fuel lines. Would be nice if Edelbrock had test units, Id love to through a 1407 on there and just see what happens, Im just hesitant to drop the coin to test it and then find out after the $ that I still have the same prob.....

I would hate to see you have trouble after you gave Edelbrock your hard earned money. I have solution to your Holley fuel line issues. Do it, go get a Holley and live happily ever after.

http://board.moparts.org/ubbthreads/sho ... in=5892724

Check out the advertisement half way down and see if that is for you.

 

[a6t9vette]

Chris, thanks for that link, that a pretty cool idea..... Well I have some news to report on my situtation. I got some time to play with the carb yesterday and did end up getting an improvement (we will see if it stays like that). I ended up changing to the lightest step up springs (blue), and after a few more varioius changes ended up with 1449 rods, and the 0.043 nozzles, with the accelerator pump on the closest hole (Biggest shot of fuel) and increased timing to about 14 Deg initial (~2 deg more then I had). There is still a slight hesitiation, but from a stop when I stomp on it it wasnts to spin the tries rather then stall....

Im going to try and move my vac advance line to the manifold vacuum port and see if that puts the icing on the cake....

 

[moparchris]

Chris, thanks for that link, that a pretty cool idea..... Well I have some news to report on my situtation. I got some time to play with the carb yesterday and did end up getting an improvement (we will see if it stays like that). I ended up changing to the lightest step up springs (blue), and after a few more varioius changes ended up with 1449 rods, and the 0.043 nozzles, with the accelerator pump on the closest hole (Biggest shot of fuel) and increased timing to about 14 Deg initial (~2 deg more then I had). There is still a slight hesitiation, but from a stop when I stomp on it it wasnts to spin the tries rather then stall....


Im going to try and move my vac advance line to the manifold vacuum port and see if that puts the icing on the cake....

Nicely done! Way to stick with it.

 

[mcmopar]

Chris, thanks for that link, that a pretty cool idea..... Well I have some news to report on my situtation. I got some time to play with the carb yesterday and did end up getting an improvement (we will see if it stays like that). I ended up changing to the lightest step up springs (blue), and after a few more varioius changes ended up with 1449 rods, and the 0.043 nozzles, with the accelerator pump on the closest hole (Biggest shot of fuel) and increased timing to about 14 Deg initial (~2 deg more then I had). There is still a slight hesitiation, but from a stop when I stomp on it it wasnts to spin the tries rather then stall....

Im going to try and move my vac advance line to the manifold vacuum port and see if that puts the icing on the cake....

Did Edelbrock tell you the closest hole on the accel pump arm creates the longest accel pump shot? From reading all the literature on the old AVS carbs the closest (top) hole in the accel pump arm produces the smallest/shortest pump shot whle the bottom hole produces the biggest/longest pump shot.

 

[SomeCarGuy]

bottom hole is the big shot.

 

[6R9Runner]

Interesting, I developed a stumble even with the 1407 (750 cfm) after swapping to a dual plane DP4B from the single-plane Streetmaster. So out of curiosity I swapped in a 1406 (600 cfm, jetted and rodded 2-3 stages rich) and drove around town yesterday with my vacuum gauge in the car, connected to the carb manifold port. I've been meaning to do this for a while and its quite interesting, you should try it. Since a carb works off of vacuum signals, you need to know what signals it gets to understand the hesitation. Of course an LM-2 air/fuel meter would be handly but I'm talking about seat-of-the pants testing for driveability. Anyhow, idling at 750 rpm my 383 generates 16 in Hg. When the car is moving and engine speed is around 2000 rpm, not pressing the gas, the vacuum increases to 19. Surprising but it makes sense, higher velocity air = lower pressure. Press the clutch and blip the throttle, the vacuum heads quickly to 5 in Hg, whereas slowly pressing on the gas shows 14-15 in Hg. It all depends on the throttle position, engine rpm and load, but the point is that a sudden opening of the throttle causes a loss of vacuum. This is not a great discovery, but how it applies with the Eddy carb is the rods jump up and you get a rich stumble (unless the step-up springs are really light). If the engine is allowed to consume the fuel then there's no problem, but with a heavy car in gear below 2000 rpm the engine can fall on its face if you drop the hammer. At 2500+ the power is coming on and the tires want to spin, so there's a fine line. Above 3000 rpm I can hammer it and there's power, baby. BTW, the hesitation i had with the Eddy 1407 on the dual plane was caused by too much fuel, how i figured this out was by completely disconnecting the pump nozzle linkage and driving around. The stumble was "nearly" gone. Not wanting to drive without an accelerator pump, and with all the car forum chatter related to the 1407/ 750 cfm Eddy being a bad carb (i.e. on 350s and 383's), it motivated me to clean up a 1406, steal a few parts from the 750 and try it out. Off-the-line its a different car, as the 750 cfm was too big for my 383 for just driving on the street.