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Need carb help

 
Old 01-01-2019, 11:06 AM
  #21  
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Originally Posted by TTur1996 View Post
Sounds like you still have something on pulling timing at that rpm. Zero every graph and turn them off. Other than timing of coarse. If that don't work your converter is way too tight and your not getting enough rpm to let it come out.
Timing is staying flat. I was also thinking about the torque converter. But I don't understand why the bog goes away after the motor is warm. It got better with your timing suggestion. I mean the motor didn't have to be full temp as long for the bog to disappear.

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Old 01-01-2019, 01:01 PM
  #22  
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[QUOTE=Doug G;20023763]

ACCELERATOR PUMP CAMS AND SHOOTERS

Accelerator pump cams come in various sizes and are color coded and number coded by Holley. The cams have different shaped ramps that the arm from the accelerator pump rides on. By changing the size and shape of the arc on the cam, the pump shot can be tailored to start early or later as you go from off idle to full throttle. Changing the cams can have an effect on the way a vehicle leaves the start line in a drag race. If you leave the line off idle or at a higher RPM (while foot braking or when using a trannie brake or when using a clutch with a manual transmission) experimenting with the pump cams can help. There is no set rule for use, you just have to experiment with the different cams and the different cam positioning holes in the throttle linkage of the carb. Holley sells individual cams or you can buy their kit which includes an assortment of cams to choose from.

Pump shooters are another area of experimentation. Holley carbs come with a standard shooter size which differs by carb list#. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. The shooters help richen this momentary condition and eliminate the stumble. Keep going up in shooter size until a puff of black smoke comes out the exhaust, then go back one or two sizes. Playing with the shooter sizes is particularly helpful, when you have an intake with a large plenum area, such as a large open plenum or a tunnel ram. Keep in mind that as you increase the shooter size, you may also need a "hollow" screw to hold the shooters in the carb. At shooter sizes over .039, Holley recommends that you use the "hollow" screw (PN-26-12) which allows more fuel to flow to the shooters.
Been playing with the cams and squirter sizes. Have the cam kit. Gone from .031 to .037. Helped with a dead stop hesitation I had originally. May have to look at the cam again. Now that I think about it. part throttle is taking up some of the ramp. Gotta dig up my diagram for cam profiles.
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Old 01-02-2019, 08:24 AM
  #23  
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Do you have the temp sensor hooked up to the 6014. If you do zero it out. That may be pulling timing for some reason. If that is a new custom carb I highly doubt it's the carb. Plus you said you tried another carb and it did the same thing. We had the same problem and it ended up being the converter.
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Old 01-02-2019, 08:53 AM
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Originally Posted by TTur1996 View Post
Do you have the temp sensor hooked up to the 6014. If you do zero it out. That may be pulling timing for some reason. If that is a new custom carb I highly doubt it's the carb. Plus you said you tried another carb and it did the same thing. We had the same problem and it ended up being the converter.
Temp is connected but the plot has been zero'd. New carb, new rebuilt motor. Old TH350 that was originally mated to a 350 SBC.
,
I haven't tried any other carb.

Did your problem go away after the motor was good and warm. I feel like I am harping on this detail but I want to understand why it does this. It reminds me of a time when I had a 69 Mercury Montego with a mild 302 in it. When I first got it taking off at low RPMS was crap and I had to choke it for a long time. One day it wouldn't start so my dad comes out and checks the points, found them out of adjusment makes them right and then all of a sudden the car runs awesome. No choke, no low RPM stumble.

Is it possible the coils are not firing at low RPM? I ask cause sticking my timing light on some of the plug wires doesn't produce a tach reading unless I rev the motor up a bit.
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Old 01-03-2019, 05:47 AM
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We always warm ours up to get the oil hot before we rip on it so no I don't know if it did it cold. Usually when it's cold the motor has a harder time accepting all the fuel being thrown at it. I have never had a vacuum secondary carb respond like a mecanical secondary double pumper carb. We went from a 650 vac secondary carb on my sons mud truck to a 850 double pumper mechanical secondary carb and wow what a difference that made. It has a dual plane intake as well. Everyone told us that carb would be too much at the time and now they just say damn. Try a different carb and see if that helps. Sorry I thought you said you tried a different one. What is the current stall you have right now? If the coils were not firing you would know it. The motor would be shaking and running like crap. You sure you don't have a vacuum leak? Check it cold before everything has a chance to expand. Fire it up and at a idle have someone watching the tach closely. Spray the **** out of the intake where it meets the heads with starting fluid and see if the rpm raises or fluctuates. If it does you have a leak. Do the same thing around the carb gasket. Have a fire extinguisher ready just to be safe. You might want to fire it up in the pitched black to make sure there is no spark escaping anywhere first to be safe also.
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Old 01-03-2019, 11:32 AM
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Originally Posted by TTur1996 View Post
We always warm ours up to get the oil hot before we rip on it so no I don't know if it did it cold. Usually when it's cold the motor has a harder time accepting all the fuel being thrown at it. I have never had a vacuum secondary carb respond like a mecanical secondary double pumper carb. We went from a 650 vac secondary carb on my sons mud truck to a 850 double pumper mechanical secondary carb and wow what a difference that made. It has a dual plane intake as well. Everyone told us that carb would be too much at the time and now they just say damn. Try a different carb and see if that helps. Sorry I thought you said you tried a different one. What is the current stall you have right now? If the coils were not firing you would know it. The motor would be shaking and running like crap. You sure you don't have a vacuum leak? Check it cold before everything has a chance to expand. Fire it up and at a idle have someone watching the tach closely. Spray the **** out of the intake where it meets the heads with starting fluid and see if the rpm raises or fluctuates. If it does you have a leak. Do the same thing around the carb gasket. Have a fire extinguisher ready just to be safe. You might want to fire it up in the pitched black to make sure there is no spark escaping anywhere first to be safe also.
I'm guessing the stall is around 2500-2800. Used the powerbrake method that I have read isn't very accurate. I'd need to borrow someone else's carb to test. Unfortunately that's a resource unavailable to me.
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Old 01-03-2019, 01:04 PM
  #27  
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Originally Posted by Doug G View Post
OK, and see it has a vacuum secondary carb.

Have you tried any different springs in the diaphragm ?
With your vacuum so high, it sounds to its reacting too fast and needs a stiffer spring...possibly.

https://www.holley.com/products/fuel...ts/parts/20-13

Some good reading here...
https://www.mortec.com/carbtip1.htm
[QUOTE=Doug G;20023763]
ACCELERATOR PUMP CAMS AND SHOOTERS

Accelerator pump cams come in various sizes and are color coded and number coded by Holley. The cams have different shaped ramps that the arm from the accelerator pump rides on. By changing the size and shape of the arc on the cam, the pump shot can be tailored to start early or later as you go from off idle to full throttle. Changing the cams can have an effect on the way a vehicle leaves the start line in a drag race. If you leave the line off idle or at a higher RPM (while foot braking or when using a trannie brake or when using a clutch with a manual transmission) experimenting with the pump cams can help. There is no set rule for use, you just have to experiment with the different cams and the different cam positioning holes in the throttle linkage of the carb. Holley sells individual cams or you can buy their kit which includes an assortment of cams to choose from.

Pump shooters are another area of experimentation. Holley carbs come with a standard shooter size which differs by carb list#. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. The shooters help richen this momentary condition and eliminate the stumble. Keep going up in shooter size until a puff of black smoke comes out the exhaust, then go back one or two sizes. Playing with the shooter sizes is particularly helpful, when you have an intake with a large plenum area, such as a large open plenum or a tunnel ram. Keep in mind that as you increase the shooter size, you may also need a "hollow" screw to hold the shooters in the carb. At shooter sizes over .039, Holley recommends that you use the "hollow" screw (PN-26-12) which allows more fuel to flow to the shooters.
UPDATE: I was messing with the vacuum secondaries cause I felt like there was a hesitation accelerating from 2000 and up turns out it helped the lower RPM bog. It's gone from a flat out stall and go, to a short stutter. I was certain the secondaries weren't the issue. I tested the opening by putting a paperclip on the shaft and took a couple quick stabs, while driving keeping it under 3000 rpm, and the clip didn't move.

Where to go now. Adjust accelerator cam or secondary springs? I have kits for both. Cam is easiest to change at the moment.

Last edited by Bobbed72; 01-03-2019 at 01:13 PM.
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Old 01-03-2019, 04:34 PM
  #28  
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I know the cam is easiest, but I would really need to know what spring is in there now for the diaphragm (also look to be sure theres not hole or tear in the diaphram)
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Old 01-03-2019, 05:04 PM
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Originally Posted by Doug G View Post
I know the cam is easiest, but I would really need to know what spring is in there now for the diaphragm (also look to be sure theres not hole or tear in the diaphram)
the purple. I tried the brown awhile back but went back cause it didn't solve the issue I was dealing with at the time. My kit is missing the plain spring. Think that's the one I need.
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Old 01-03-2019, 05:20 PM
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You said you had a screw to adjust vacuum rate ?

You could try turning it all the way in and 1 full turn out as a starting point ?
Keep turning 1 full turn each test until it gets better.. keep testing until it gets bad again...turn in 1/2-3/4 turn. Set !
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Old 01-03-2019, 06:11 PM
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Originally Posted by Doug G View Post
You said you had a screw to adjust vacuum rate ?

You could try turning it all the way in and 1 full turn out as a starting point ?
Keep turning 1 full turn each test until it gets better.. keep testing until it gets bad again...turn in 1/2-3/4 turn. Set !
one full turn is where it was bad. It's a half turn out now. Not sure where the optimal adjustment range is. I can try a quarter turn. Heard the screw adjustment is about a half a spring size so I think the next spring up would be good.
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Old 01-03-2019, 06:41 PM
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Yes, if its almost closed, need to get a stiffer spring.

You could try 1/8, 1/4, 1/3 and see if it gets happier....won't hurt.
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Old 01-06-2019, 03:01 PM
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Originally Posted by Doug G View Post
Yes, if its almost closed, need to get a stiffer spring.

You could try 1/8, 1/4, 1/3 and see if it gets happier....won't hurt.
Tried the 1/4 then 3/8 then back the other way at 1/8. I think it's happier there for now but I haven't really tested it. New springs should be here tomorrow. Gonna go one up and see where it wants to be on the screw. Will be awhile before I can road test it. Raining all week.

I'd buy everyone who helped a beer if I could. Think the only person who is near me though is PDX.
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