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holley 750 vac issues #1366121
01/07/13 10:51 PM 01/07/13 10:51 PM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

Joined: May 2011
Posts: 625
Oakville, Wa
Ive never really dinked around with vacuum secondary carbs much. I just went through one for my 63 413 4 speed. It idles and starts good but has a cruise stumble. When cruising steady throttle at 2000 rpms and I try excellerating slowly it cuts out. If I mash it it goes. Its that mid rpm cruising range that seems to be the problem..

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366122
01/07/13 10:57 PM 01/07/13 10:57 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
Master
MR_P_BODY  Offline
Master

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Posts: 52,972
Romeo MI
Sounds like the pump shot is late... make sure as soon
as the throttle moves its getting the pump shot
Re: holley 750 vac issues [Re: MR_P_BODY] #1366123
01/07/13 11:35 PM 01/07/13 11:35 PM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

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Posts: 625
Oakville, Wa
I have the pump arm gap at .015

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366124
01/07/13 11:39 PM 01/07/13 11:39 PM
Joined: Feb 2005
Posts: 4,316
Prospect, PA
BSB67 Offline
master
BSB67  Offline
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Prospect, PA
Is it a Holley - 3310? A slight stumble while cruising with light throttle can be caused by some junk in the carb causing a lean condition in the transition or possibly main circuit. That has been my experience more than once on Holleys.
Re: holley 750 vac issues [Re: BSB67] #1366125
01/07/13 11:51 PM 01/07/13 11:51 PM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

Joined: May 2011
Posts: 625
Oakville, Wa
yes its a 3310. I had it all apart and it was cleaned and reassembled.

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366126
01/08/13 12:10 AM 01/08/13 12:10 AM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
Master
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Master

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Posts: 52,972
Romeo MI
Are you good getting up to cruise and then it wont
take any pedal... could be your secondary is opening
to easy... put a slightly stiffer spring in it
Re: holley 750 vac issues [Re: MR_P_BODY] #1366127
01/08/13 12:57 AM 01/08/13 12:57 AM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

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Posts: 625
Oakville, Wa
It seems to stumble at lower rpms. Unfortunatly The weather has been crappy and I havent had much chance to drive it since I got it running. It runs great in the shop. Idle and throttle response is great but under load its a different story.

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366128
01/08/13 01:03 AM 01/08/13 01:03 AM
Joined: Aug 2003
Posts: 12,291
Kent, Wa
340SHORTY Offline
Truck Nut
340SHORTY  Offline
Truck Nut

Joined: Aug 2003
Posts: 12,291
Kent, Wa
I had that problem. I went up to the next size squirter and adjusted the pump screw to let it squirt sooner..

I am truckless..
Re: holley 750 vac issues [Re: 340SHORTY] #1366129
01/08/13 01:11 AM 01/08/13 01:11 AM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

Joined: May 2011
Posts: 625
Oakville, Wa
I thought about trying a bigger squirter. I guess I'll try closing up that pump gap also since Mr p mentioned that too. I know bigger squirters helped my starting line bog on my 980 double pumper..

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366130
01/08/13 03:43 AM 01/08/13 03:43 AM
Joined: Dec 2003
Posts: 531
USA
5
540DUSTER Offline
mopar
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mopar
5

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Posts: 531
USA
the gap is measured with the throttle open all the way,not at idle.
Re: holley 750 vac issues [Re: MR_P_BODY] #1366131
01/08/13 08:49 AM 01/08/13 08:49 AM
Joined: May 2004
Posts: 12,394
Taxes & Virus's R-US, NY
Dragula Offline
I Live Here
Dragula  Offline
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Taxes & Virus's R-US, NY
On Mopar's a vacuum carb should never be used...But it also sounds like you squirter shot is a little late or small or both.

'70 Cuda,...605 EFI Hemi Street Car (6.20 best pass, 1.33 60ft)
https://www.youtube.com/watch?v=WYw6RA-k5Bk (6.25 at 108.75mph from inside car)
https://www.youtube.com/watch?v=3zQEb9uxFng (6.25 at 108mph from outside car)
https://www.youtube.com/watch?v=JCvfzsC4NgM (9.9)

'66 Barracuda AWB Stretched nose Blown 440 Car in build stage

'71 Duster Drag Car 400 Low Deck 512 best 6.002 at 115.44mph
https://www.youtube.com/watch?v=Znuo3jMUXTk
Re: holley 750 vac issues [Re: Dragula] #1366132
01/08/13 02:37 PM 01/08/13 02:37 PM
Joined: Jan 2003
Posts: 16,376
D
dogdays Offline
I Live Here
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There are also about 10 different accelerator pump cams to try.

R.
Re: holley 750 vac issues [Re: HOTMOPR] #1366133
01/08/13 04:39 PM 01/08/13 04:39 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
Master
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Romeo MI
Quote:

It seems to stumble at lower rpms. Unfortunatly The weather has been crappy and I havent had much chance to drive it since I got it running. It runs great in the shop. Idle and throttle response is great but under load its a different story.



Also make sure you have enough timing
Re: holley 750 vac issues [Re: 540DUSTER] #1366134
01/08/13 05:42 PM 01/08/13 05:42 PM
Joined: Jun 2003
Posts: 9,225
Charleston
S
sixpackgut Offline
Drag Week Mod Champion
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S

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Posts: 9,225
Charleston
Quote:

the gap is measured with the throttle open all the way,not at idle.



this

Gen 3 power 6.22@110, 9.85@135
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performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
Re: holley 750 vac issues [Re: Dragula] #1366135
01/08/13 05:46 PM 01/08/13 05:46 PM
Joined: Dec 2009
Posts: 20,640
in a cattle trailer down by th...
G
Guitar Jones Offline
Paddle faster! I hear banjo music!
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in a cattle trailer down by th...
Quote:

On Mopar's a vacuum carb should never be used...But it also sounds like you squirter shot is a little late or small or both.



Uh why? I've used vacuum sec carbs for years on my race car to slow it down. A screw and a lock nut on the vacuum pod cap stops the opening very well.

"Follow me the wise man said, but he walked behind"


'92 D250 Club Cab CTD, 47RH conversion, pump tweaks, injectors, rear disc and hydroboost conversion.
'74 W200 Crew Cab 360, NV4500, D44, D60 and NP205 divorced transfer case. Rear disc and hydroboost conversion.
2019 1500 Long Horn Crew Cab 4WD, 5.7 Hemi.
Re: holley 750 vac issues [Re: Guitar Jones] #1366136
01/09/13 12:15 AM 01/09/13 12:15 AM
Joined: Mar 2004
Posts: 2,475
SW Ohio
C
cgall Offline
top fuel
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SW Ohio
There are a whole range of different springs that are color-coded to vary the opening timing and duration of the the secondaries. They have a dab of paint on the small end of the spring. IIRC, the gold spring was the lightest one that was used at the strip. You might check your carb gaskets and hoses to make sure you don't have an air leak there. I run a 950HP carb that has a vac-sec pot on it, silver spring. It has been 10.24 at 128 MPH on my Duster.
Re: holley 750 vac issues [Re: HOTMOPR] #1366137
01/21/13 11:33 PM 01/21/13 11:33 PM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

Joined: May 2011
Posts: 625
Oakville, Wa
Quote:

I thought about trying a bigger squirter. I guess I'll try closing up that pump gap also since Mr p mentioned that too. I know bigger squirters helped my starting line bog on my 980 double pumper..



PUNTING!! I give up on the 750! I went back to my 850 dbl pumper. Problem I am having with this carb is I cant get it to idle down. I welded up the drilled primary throttle blades. The secondaries are not drilled and it doesnt have the secondary idle adjustment. Right now the best I can get it is 1100 rpms. Which might be fine in a auto with a bigger cam but the 4 speed likes about 800. Any ideas why it wont idle down. No cables were hooked up so nothing is binding. blades appear to be closed when looking down inside.. I also sprayed carb cleaner around it and no vacuum leaks.. Any Ideas?

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: holley 750 vac issues [Re: HOTMOPR] #1366138
01/21/13 11:41 PM 01/21/13 11:41 PM
Joined: Jun 2008
Posts: 3,916
usa
L
lewtot184 Offline
master
lewtot184  Offline
master
L

Joined: Jun 2008
Posts: 3,916
usa
Quote:

I have the pump arm gap at .015

if you have an air gap between the arm and pump lever at idle, thats wrong. no air gap.
Re: holley 750 vac issues [Re: lewtot184] #1366139
01/22/13 12:09 AM 01/22/13 12:09 AM
Joined: Jan 2003
Posts: 9,826
las vegas
70AARcuda Offline
master
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Posts: 9,826
las vegas
flip the carb over..there is a set screw that allows the rear throttle blades to be opened to help with the idle..see if some one has opened them up too much...

Tony

70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
Re: holley 750 vac issues [Re: 70AARcuda] #1366140
01/22/13 12:11 AM 01/22/13 12:11 AM
Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR Offline OP
mopar
HOTMOPR  Offline OP
mopar

Joined: May 2011
Posts: 625
Oakville, Wa
No air gap and this 850 doesnt have the secondary idle adjustment..

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
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