Accelerator pump nozzle question
#2404550
11/16/17 05:38 PM
11/16/17 05:38 PM
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Joined: Mar 2009
Posts: 889
Oh
parksr5
OP
super stock
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OP
super stock
Joined: Mar 2009
Posts: 889
Oh
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This Winter is going to kill me. I just put new heads and intake on the car. I beat feet to get it done and go to the track before the end of the year but, the track closed early so; I’ll have to wait until Spring. I keep thinking about things and probably will all Winter until I can make it to the track (my sickness just keeps getting worse as I get older).
Anyway, with the swap, the motor wants more fuel and I got my off idle flat spot back. When I first got the motor down in the car years ago, I had to mess with the carb (850 Street HP) to get the off idle lean bog to go away. This bog was confirmed on a chassis dyno; the afr would spike to 17 or so and then come back down to where it should be. It ended up taking 40 pump squirters front and back and a 50cc diaphragm up front to cure the bog. Now, before I ran out of time, I ended up with 47’s both front and back and changed the back diaphragm to a 50cc and the flat spot was close to being gone but, not all the way.
Next spring, I want to mess with the cams as I know 50cc diaphragms should be used with the brown and yellow cams (maybe one other one too if I can remember right) which are not currently on the car right now.
My question is, does this sound like too much squirter to you? Is there some other adjustment I can mess with to get the squirter size down? I just feel like I’m missing something.
FYI, the timing is at 18 initial and 38 total (I’ll probably knock the total down to 36), my idle adjustment screws are at about ¾ of the way out (I set the screws using a vacuum gauge) and my transfer slot exposure is correct.
Mild 470 low deck with ported 906’s, an Edlebrock DP4b, comp xe hydraulic flat tappet (if I can remember right, its 230/236 at 50); nothing too wild.
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Re: Accelerator pump nozzle question
[Re: parksr5]
#2405068
11/17/17 04:57 PM
11/17/17 04:57 PM
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Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR
master
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master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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This Winter is going to kill me. I just put new heads and intake on the car. I beat feet to get it done and go to the track before the end of the year but, the track closed early so; I’ll have to wait until Spring. I keep thinking about things and probably will all Winter until I can make it to the track (my sickness just keeps getting worse as I get older).
Anyway, with the swap, the motor wants more fuel and I got my off idle flat spot back. When I first got the motor down in the car years ago, I had to mess with the carb (850 Street HP) to get the off idle lean bog to go away. This bog was confirmed on a chassis dyno; the afr would spike to 17 or so and then come back down to where it should be. It ended up taking 40 pump squirters front and back and a 50cc diaphragm up front to cure the bog. Now, before I ran out of time, I ended up with 47’s both front and back and changed the back diaphragm to a 50cc and the flat spot was close to being gone but, not all the way.
Next spring, I want to mess with the cams as I know 50cc diaphragms should be used with the brown and yellow cams (maybe one other one too if I can remember right) which are not currently on the car right now.
My question is, does this sound like too much squirter to you? Is there some other adjustment I can mess with to get the squirter size down? I just feel like I’m missing something.
FYI, the timing is at 18 initial and 38 total (I’ll probably knock the total down to 36), my idle adjustment screws are at about ¾ of the way out (I set the screws using a vacuum gauge) and my transfer slot exposure is correct.
Mild 470 low deck with ported 906’s, an Edlebrock DP4b, comp xe hydraulic flat tappet (if I can remember right, its 230/236 at 50); nothing too wild.
I'm no carb expert by no means. I get by with trial and error, mostly the latter!!!!My friend has the same carb with the same problem. He has a small block stroker. I ended up with .036" IFR's with stock jetting, 35 squirters up front and 37 out back. 50 cc pump on the secondaries with brown cam. Timing was at 36, if I recall, mostly all out just off idle. Hope this points you in the right direction
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: Accelerator pump nozzle question
[Re: parksr5]
#2405176
11/17/17 08:57 PM
11/17/17 08:57 PM
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Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR
master
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master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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In some cases the bigger ifrs/idle bleed combos help as you found out and lately I've been putting in bigger ifr's to help out the idle/transition circuits and to come up on the boosters happier instead of a big lean dip. However, this apply's to some and others may need to be leaner for various reasons but the wide band and plug reading go a long way here and a chassis dyno better yet........  When you add bigger ifrs, what does it do to the idle fuel screws; do you normally have to turn them in some more? In all my cases,(going lean off idle), the idle mixture screws didn't need adjusted much, if at all. The idle mixture screws can help very little with off idle boggs. They actually control the volume of air/fuel mixture being delivered at idle to the small holes below the throttle blades. The IFR's affect fuel to transition slots. If I'm wrong with this description, I'm sure someone will jump in and correct me.....
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: Accelerator pump nozzle question
[Re: 68LAR]
#2405278
11/18/17 01:46 AM
11/18/17 01:46 AM
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Joined: Aug 2003
Posts: 43,157
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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I have found working on the idle air bleeds affect the AFR from idle to WOT, not sure about the idle fuel feed restriction channels on how they affect the AFR at WOT   I did see a measureable difference in the AFR readings by leaning them down at idle and part throttle cruise also, CRS on WOT 
Last edited by Cab_Burge; 11/18/17 01:49 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Accelerator pump nozzle question
[Re: parksr5]
#2405289
11/18/17 02:08 AM
11/18/17 02:08 AM
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Joined: Jul 2004
Posts: 19,317
State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,317
State of confusion
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In some cases the bigger ifrs/idle bleed combos help as you found out and lately I've been putting in bigger ifr's to help out the idle/transition circuits and to come up on the boosters happier instead of a big lean dip. However, this apply's to some and others may need to be leaner for various reasons but the wide band and plug reading go a long way here and a chassis dyno better yet........ When you add bigger ifrs, what does it do to the idle fuel screws; do you normally have to turn them in some more? For me if the mixture screws have to be turned too far in say 1/2 turn from seated then I size down the ifr's and if they need to be like 2 turns out then bigger ifr's as a starting point. I size the idle bleeds according to the ifr's and go from there seeing/feeling the differences good and bad. I find the mixture screws play a HUGE role in how rich/lean the idle, transfer and cruise is on my Dart and there's a big difference between 1 3/4 turns out and 2 turns once it has heat in it. Same w/leaner mixtures, my car recovers faster when the happy peddle is mashed being in the 12-13 afr range while leaving a stop light and cruising instead of the 14-15's........... 
Last edited by Thumperdart; 11/18/17 02:13 PM.
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Accelerator pump nozzle question
[Re: parksr5]
#2405398
11/18/17 12:38 PM
11/18/17 12:38 PM
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Joined: Jan 2003
Posts: 12,074
Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,074
Benton, IL.
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I have been dealing with this same issue on my Dominator. With the cruise and idle happy, I had a lean spike just off idle. Tried quite a few things, but if I got the transition happy, something else was fat.
I went to my Holley book and noted that they make accel squirters to.050. So I broke out the drill bits. By .044, I couldn't feel a stumble any more, but could still see a spike on the LM log. At.050 there was very little spike left, but when easing around town, the graph will go to 10 or so A/F. Too fat, but the least of all the compromises I have found.
Also, if you do not have the 50cc cams, you are not getting the full shot from the 50cc pump.
Master, again and still
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Re: Accelerator pump nozzle question
[Re: Thumperdart]
#2406887
11/21/17 04:02 PM
11/21/17 04:02 PM
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Joined: Mar 2009
Posts: 889
Oh
parksr5
OP
super stock
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OP
super stock
Joined: Mar 2009
Posts: 889
Oh
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For me if the mixture screws have to be turned too far in say 1/2 turn from seated then I size down the ifr's and if they need to be like 2 turns out then bigger ifr's as a starting point. I size the idle bleeds according to the ifr's and go from there seeing/feeling the differences good and bad. I find the mixture screws play a HUGE role in how rich/lean the idle, transfer and cruise is on my Dart and there's a big difference between 1 3/4 turns out and 2 turns once it has heat in it. Same w/leaner mixtures, my car recovers faster when the happy peddle is mashed being in the 12-13 afr range while leaving a stop light and cruising instead of the 14-15's........... [/quote] This is where I get confused. So; in my situation, I have a lean bog off idle but, my idle mixture screws are around a 1/2 to 3/4's of a turn from being seated. If you sized down the IFR's, then less fuel would be supplied to the transfer too and wouldn't that just make the condition worse?
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Re: Accelerator pump nozzle question
[Re: parksr5]
#2406926
11/21/17 05:41 PM
11/21/17 05:41 PM
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Joined: Jan 2003
Posts: 14,496
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,496
So. Burlington, Vt.
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IMO, since the build is slowly morphing into a FAST combo anyway, might as well get that AVS bolted on and start sorting it out now.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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