Carb Loading Up

[Pyetime 10]

Its seems I cant find a happy adjustment for my Holley 4150 double pumper. When your just coasting coming up to a stop or slowing down and then you go to get on the gas the car stumbles and I have to push the clutch in and rap up the motor to clean it out. Seems like shes getting too much fuel. Any thoughts on a good carb adjustment to make?

[Print Dad 58]

Hello Pyetime,

I think the very first thing to check is the height of the fuel in the bowls

 

Pretty simple to do - - remove the small brass screw on the pass side of the

front bowl - -the gas in the bowl should be just at the bottom of the opening.

Be CAREFUL - there is a small washer behind the screw. If not sure - bounce

on the fender gently so that the motor rocks a little. I am thinking your

gas will come pouring out of the sight screw HOLE - when you take the

screw out.

Of course you need to check the height in BOTH bowls.

If the gas pours out - -you need to adjust the float level with the

screw and nut on top of the bowl. There are LOADS of instructions to do this

 

I would then make certain that your idle mixture screws (4 total) are all set

VERY close to the same amount. The normal starting position is 1 and a half turns backed out from a GENTLE seated adjustment.

 

When you adjust - all the screws should be the same amount from a seated position.

 

CHECK The bowl heights and let us know

 

Print DAd

[Pyetime 10]

Print Dad-Thanks

I checked both bowls and did have to rock the car a bit to see any fuel, so I he would assume that the float levels are where they need to be. I also adjusted the front mixture screws, however the two screws on the back side are gone!! This cant be right? Am I missing those 2 screws or is this normal?

Edited August 18, 2013 by Pyetime

[blueblood 26]

Are you sure its a 4150 Double pumper?

See attached exploed view diagram, appears to be a Vac secondary carb with only two idle mixture screws.

http://www.holley.com/data/TechService/Technical/4150%204160%20Exploded%20View.pdf

[bomccorkle 12]

Also sounds, if I am reading right, that you are having issues under acceleration? If so it sounds that it could need an accelerator pump adjustment. Also a lot of guys like to have their idle too low(to get the thumpity thumpity) that can also cause an apparent load up condition. For reference I can't think of a single carb style engine that should be idling at less than 700-800 rpm. Of course bigger bumpstick means a higher idle to help compensate for vacuum deficiencies in the manifold. Also on accelerator pumps the nozzles are interchangeable for orifice diameter and spray style. Start with the smallest misting type and work up from there. You will notice the difference between a lean and fat stumble off idle. Also you say a double pumper. Do you mean true mechanical secondary double pumper or a vacuum? Mechanicals are great for tons of tunability and a stick shift but either an auto or a street car really benefits from a vacuum secondary style carb. (And yes the secondaries are still very tunable.) Also make sure your fuel rail pressure is stable. I have had some mechanical pumps pump way better than expected and cause an overfull in the float bowls then causing an overly fat idle that hence caused a stumble I could not find.... Now I always run a regulator on the front of my fuel rail and a pressure gauge as well.

 

Just remember carbs are relatively simple they just take patience and the best is when your tuning you get a great excuse to flog the car around the block:-)

[Pyetime 10]

Are you sure its a 4150 Double pumper?

See attached exploed view diagram, appears to be a Vac secondary carb with only two idle mixture screws.

http://www.holley.com/data/TechService/Technical/4150%204160%20Exploded%20View.pdf

 

yeah, positive!

[Pyetime 10]

Also sounds, if I am reading right, that you are having issues under acceleration? If so it sounds that it could need an accelerator pump adjustment. Also a lot of guys like to have their idle too low(to get the thumpity thumpity) that can also cause an apparent load up condition. For reference I can't think of a single carb style engine that should be idling at less than 700-800 rpm. Of course bigger bumpstick means a higher idle to help compensate for vacuum deficiencies in the manifold. Also on accelerator pumps the nozzles are interchangeable for orifice diameter and spray style. Start with the smallest misting type and work up from there. You will notice the difference between a lean and fat stumble off idle. Also you say a double pumper. Do you mean true mechanical secondary double pumper or a vacuum? Mechanicals are great for tons of tunability and a stick shift but either an auto or a street car really benefits from a vacuum secondary style carb. (And yes the secondaries are still very tunable.) Also make sure your fuel rail pressure is stable. I have had some mechanical pumps pump way better than expected and cause an overfull in the float bowls then causing an overly fat idle that hence caused a stumble I could not find.... Now I always run a regulator on the front of my fuel rail and a pressure gauge as well.

 

Just remember carbs are relatively simple they just take patience and the best is when your tuning you get a great excuse to flog the car around the block:-)

 

 

The carb is a mechanical secondary setup . I think I need to look into a regulator and a gauge. Should be around 5-7 PSI from what I'm reading?

[bomccorkle 12]

Yes. 5-7 also look thru all that I have mentioned and being a mech secondary check the secondary accelerator pump as well. Unless you're running a fire breathing big inch stroker motor 30 cc acc pumps are more than adequate . and as mentioned there is a ton of tunability just in the acc pumps. From what I have seen this is the predominant area for stumbled remember that when you give the car any accelerator the carb is no longer working due to the vacuum loss. The accelerator pump is there just to cover this hole in the fuel map. At a half throttle are you still getting a fat condition??

[bomccorkle 12]

Also I forgot to say. Check your linkage and make sure there isn't an issue there. I've seen many of these that somebody has taken the get-r-done attitude and monkey banged the damn linkage to attempt to fix something that isn't broken....

[buening 63]

Look at the metering block with the missing idle screws, and check if you see threads in the holes. My street avenger vacuum secondary has a rear metering block (unlike some vac sec holleys), and that rear metering block has provisions for idle screws but had not been drilled and tapped. Give us the numbers off the body so we can determine what you have exactly.

[bomccorkle 12]

Funny buening with the amount of tinkering you do I'd have figured you for a demon kinda guy....

[buening 63]

Actually I suck with carbs. One of the things I haven't tinkered enough with. As with all things, it comes with experience :)

[bomccorkle 12]

Very true. But your a quick guy. If the need arises I really can't say enough good things about the speed demons for street/strip style applications. The tuneability is unreal(and a bit unforgiving) I found an excellent book that I bought that explained a ton and helped me to get rolling on one. It should work for Holley's too(being as a demon is just a tricked 4150) its called something like how to tune and win with demon carbs or something to that effect. Mine has tattered pages from going thru it so many times....

[Pyetime 10]

Look at the metering block with the missing idle screws, and check if you see threads in the holes. My street avenger vacuum secondary has a rear metering block (unlike some vac sec holleys), and that rear metering block has provisions for idle screws but had not been drilled and tapped. Give us the numbers off the body so we can determine what you have exactly.

 

The only numbers on the actual body I see are on the Driver side and it reads P 32. There are several other areas that have numbers stamped as well. Sorry I feel like a pain in the arsss. I appreciate everyones help!

[buening 63]

Typically it is stamped as shown below:

 

 

Example:

 

[Max Power 74]

Not covered yet here is the power valve. You should be running about a 6 to 6.5 on stocker applications, and half of your in gear idle vacuum on performance applications.

 

Example, if you are running 10' of vacuum in gear at idle, a 4.5" power valve should work.

 

Also, if it has been running just plain too rich since you installed it, you may need to look at leaner jets.

[bomccorkle 12]

Also to check a power valve start the car and let it idle then close the idle metering screws. If it keeps running the power valve is toast if it dies its still functioning. And max is correct. The PV is half the value of the car idling under load if auto (in gear) and step down one half not up one half if the situation arrives.

[Pyetime 10]

Here's the stamp info:

 

4777-7

3401

 

More great news, I guess I didn't do my homework like I should have. I bought a fuel regulator (Holley) from Jegs and after looking through the instructions realized that you need an electric fuel pump and not a mechanical like I have. Oh well, it was only $30 and I may need it down the road.

Edited August 24, 2013 by Pyetime

[cavboy78 28]

pyetime,

 

I am dealing with the exact same issue as you right now, but been so damn busy at work, I've had no time to get things fixed.

 

1- I just ordered all the bits and pieces for a fuel regulator addition since I was running at about 9 psi. I haven't hooked it all up yet, but I bought the holley 12-803 and should work with a mechanical fuel pump.

2- I also have the 4150 dp and when trying to make some adjustments, noticed that there were no idle screws for the secondaries as well. I will check for the numbers tonight when I get home.

[buening 63]

Pyetime, the 4777-7 650cfm Holley carb only has 2-corner idle.....thus only two idle screws.

 

Regarding the fuel regulator, what PSI is it's range and what fuel pump do you currently have? It simply makes sure the PSI doesn't go over the number you set it at. It doesn't care if an electric or mechanical pump is pushing the fluid through it....it just regulates the pressure going through it. They are more commonly used with electric pumps, but will work with mechanical pumps.

 

 

Regarding what your car is doing, if you sit at a stop light for a minute or so and then floor it, does it bog or does it take off with no hesitation? What about if you are coasting at, say 30mph, and you floor it? Responsive or bogs?

[Pyetime 10]

pyetime,

 

I am dealing with the exact same issue as you right now, but been so damn busy at work, I've had no time to get things fixed.

 

1- I just ordered all the bits and pieces for a fuel regulator addition since I was running at about 9 psi. I haven't hooked it all up yet, but I bought the holley 12-803 and should work with a mechanical fuel pump.

2- I also have the 4150 dp and when trying to make some adjustments, noticed that there were no idle screws for the secondaries as well. I will check for the numbers tonight when I get home.

 

Sounds like we are both headed in the same direction. Same carb/issues and that is the regulator I bought. I need to get a gauge hooked up to see what kind of pressure Im at. Where are you going to mount the reg?

 

Im a Rochester native, spent my first 19 years there and been out in Colorado for 21. What town in Northern NY?

Edited August 26, 2013 by Pyetime

[Pyetime 10]

Pyetime, the 4777-7 650cfm Holley carb only has 2-corner idle.....thus only two idle screws.

 

Regarding the fuel regulator, what PSI is it's range and what fuel pump do you currently have? It simply makes sure the PSI doesn't go over the number you set it at. It doesn't care if an electric or mechanical pump is pushing the fluid through it....it just regulates the pressure going through it. They are more commonly used with electric pumps, but will work with mechanical pumps.

 

 

Regarding what your car is doing, if you sit at a stop light for a minute or so and then floor it, does it bog or does it take off with no hesitation? What about if you are coasting at, say 30mph, and you floor it? Responsive or bogs?

 

Hey buening, the reg. is rated at 4.5 - 9 psi. Its the 12-803 Holley model. Does the reg. need to be mounted after the fuel pump or could I find a location near the washer fluid res. where the fuel line comes through the inner fender? Heres the pump info, its an Edelbrock unit.

 

"Designed to match Performer Series carburetors, Edelbrock's High-Performance Street Fuel Pumps have 6-valves and a flow capacity of 110 gph. The unique valve design improves flow quantity and quality, and will support engines up to 600hp. High-volume, 3/8'' NPT inlet and outlet surpasses the capacity of conventional models. Produces 6 psi. For gasoline or mixed fuels only. No Regulator required. Clockable lower housing can be rotated in 60° increments for best inlet/outlet alignment."

 

If after stopped at a light and you were to take off in a rational manner you could go through the gears and you probably wouldn't notice much of an issue. Its more when you are getting on it and the secondaries open up I would say. Also I tend to notice when climbing a hill at around 20-35 mph it starts bogging or loading up with fuel. This stuff is so frustrating trying to communicate and diagnose. Troubleshooting is not my strength! I did pick up a Holley manual on ebay, $5.00:clap:, hope its beneficial.

Edited August 26, 2013 by Pyetime

[buening 63]

Well if you don't have the regulator mounted and hooked up, then I'd just return it or resell it. You'd only need one with a mechanical fuel pump that is a high-pressure model, like this one.

 

Carbs are a pain to diagnose, especially trying to describe what its doing over the internet. I'm fighting my own carb issues at the moment, so I can relate

[cavboy78 28]

Pyetime,

 

I plan on trying to mount the regulator after the fuel pump, somewhere by the front of the ds cylinder head. All your symptoms that you're troubleshooting sound very similar to mine as well.

 

Funny enough, I just moved from colorado springs last year. I've been through colorado city a few times on my way to the sand dunes/blanca peak, etc... beautiful area! My folks live just east of rochester in the sodus bay area and I'm up in watertown.

[Pyetime 10]

Pyetime,

 

I plan on trying to mount the regulator after the fuel pump, somewhere by the front of the ds cylinder head. All your symptoms that you're troubleshooting sound very similar to mine as well.

 

Funny enough, I just moved from colorado springs last year. I've been through colorado city a few times on my way to the sand dunes/blanca peak, etc... beautiful area! My folks live just east of rochester in the sodus bay area and I'm up in watertown.

 

Small world huh! If you beat me to it let me know how the regulator works out.