Carburator frustration

[Backyardmech]

I recently installed a new Edelbrock 1409 on my 2003 VP 5.0 gl. The old carb was a 500 cfm holley 2 barrel that the power valve kept sticking. Under full throttle the engine bogs down and it is a struggle to get it on plane. If i increase the throttle while on plane it accelerates at first then bogs down again. Timing is about 10⁰ BTC.

 

[tpenfield]

So you went from a 2 bbl carb to a 4 bbl . . . Did you also install a new intake manifold?

 

[Backyardmech]

So you went from a 2 bbl carb to a 4 bbl . . . Did you also install a new intake manifold?

For some reason it came from the factory with a 2 barrel mounted on a 4 barrel intake with and adapter plate.

 

[Backyardmech]

For some reason it came from the factory with a 2 barrel mounted on a 4 barrel intake with and adapter plate.

Look exactly like this one except mine has volvo penta cast into it

 

[Scott06]

Volvo penta used a 4 bbl intake with and adapter to neck down to a 2 bbl.

i run a 1409 on my mercruiser it worked well out of the box, i just went with a larger accelerator pump nozzle .

I does it idle ok ? I would check your fuel pressure should have around 5-6 psi at wot.

also check your ignition system components for wear if you haven't. Do yiu have like 26-28 degrees total ignition advance all in by 2800 rpm or so?

 

[Scott Danforth]

the 1409 may be marginal for the 5.0.

 

[Backyardmech]

Volvo penta used a 4 bbl intake with and adapter to neck down to a 2 bbl.

i run a 1409 on my mercruiser it worked well out of the box, i just went with a larger accelerator pump nozzle .

It idles fine, the electric fuel pump is new. The tach doesnt work but i set timing to 10⁰. I verified with the timing light that the timing does advance as the rpm increases. Could improper secondary fuel mix cause my issues?

 

[Bondo]

Ayuh,..... When it bogs, it's tellin' ya it's probably goin' lean

It idles fine, the electric fuel pump is new. The tach doesnt work but i set timing to 10⁰. I verified with the timing light that the timing does advance as the rpm increases. Could improper secondary fuel mix cause my issues?

Ayuh,.... Welcome Aboard,....... Yes, the fuel mix is probably the problem,....

 

[Backyardmech]

Ayuh,..... When it bogs, it's tellin' ya it's probably goin' lean

Ayuh,.... Welcome Aboard,....... Yes, the fuel mix is probably the problem,....

Any idea why a new carb would run lean?

 

[Scott06]

Any idea why a new carb would run lean?

Fuel supply to the carb, i know you said the fuel pump was replaced but have you measured the fuel pressure while running? What dot he contents of your fuel filter look like ?
what do your plugs look like In terms of reading them for mixture clues?
on my 5.0 i did not have to rejet when i installed a 1409, just a bigger accelerator pump nozzle to get rid of a off idle bog. Id be surprised if you need to unless there is an issue with dirt in the carb it should work very well on your engine out of the box.
what necessitated the fuel pump replacment

 

[Scott06]

It idles fine, the electric fuel pump is new. The tach doesnt work but i set timing to 10⁰. I verified with the timing light that the timing does advance as the rpm increases. Could improper secondary fuel mix cause my issues?

When you set the timing did u put it in base mode ?

 

[Backyardmech]

Fuel supply to the carb, i know you said the fuel pump was replaced but have you measured the fuel pressure while running? What dot he contents of your fuel filter look like ?
what do your plugs look like In terms of reading them for mixture clues?
on my 5.0 i did not have to rejet when i installed a 1409, just a bigger accelerator pump nozzle to get rid of a off idle bog. Id be surprised if you need to unless there is an issue with dirt in the carb it should work very well on your engine out of the box.
what necessitated the fuel pump replacment

Old pump was cracked. I haven't checked the pressure but the flow is strong

 

[jhande]

Going from a Holley 500 CFM to an Edelbrock 600 CFM shouldn't be a problem.

Bogging during throttle increase, especially quick increase can be caused by a few problems. Ignition system, fuel system before the carburetor, vacuum leak below the throttle plate, lean condition in the carburetor, flooding condition in the carburetor.

The Edelbrock carb is just a rebranded Quadrajet carb. Your carb is vacuum secondaries without actual adjustments. A Holley carb is fully adjustable and customizable (easier for me to work with). Back in the day working on Q-jets the only things I remember being able to do was change the metering rods and carefully bending the secondary linkage.

But before jumping into messing with the carb, double check the fuel system and ignition system. Check the carb by looking down the airhorn, manually increasing the throttle linkage and watching the fuel flow on the primary side. Is the fuel flow consistent or does it stop with any dead spots? Does it dump an excess anywhere through the increase of throttle? If a dead spot the float might need to be adjusted. It is almost impossible to do the same check on the secondary side. Usually the secondaries are checked using a vacuum meter and the motor under load (being driven). Comparing the vacuum reading to when the bog a cures. Slightly bending the linkage and testing again.

Messing with the carb is a bit difficult for me to really explain. Diagnosing the problem really needs a hands on approach. Just hoping I kind of explained and gave you a few pointers.

 

[Backyardmech]

When you set the timing did u put it in base

Going from a Holley 500 CFM to an Edelbrock 600 CFM shouldn't be a problem.

Bogging during throttle increase, especially quick increase can be caused by a few problems. Ignition system, fuel system before the carburetor, vacuum leak below the throttle plate, lean condition in the carburetor, flooding condition in the carburetor.

The Edelbrock carb is just a rebranded Quadrajet carb. Your carb is vacuum secondaries without actual adjustments.

Thank you for your response. The edelbrock has 2 metering rods i could be wrong but i thought the right rod metered the secondary fuel flow. When i first installed this carb( 1 week ago) i had hesitation and bog when the secondary opened under load. But the boat would plane in a reasonable amount of time with just the primary.
After on plane i could open the secondary and it would hesitate at first but then seemed to function normally (gps top speed 47 mph). I took the boat out this weekend to try some tuning to help the hesitation. It would barely get on plane and no matter when you opened the secondary it would lose power and bog down. I only had adjusted the idle mix at that point and i have since put it back where it started. I am considering purchasing the 1488 tuning kit in the hopes that more fuel flow will help but any advice is very welcome.

 

[Bondo]

Thank you for your response. The edelbrock has 2 metering rods i could be wrong but i thought the right rod metered the secondary fuel flow. When i first installed this carb( 1 week ago) i had hesitation and bog when the secondary opened under load. But the boat would plane in a reasonable amount of time with just the primary.
After on plane i could open the secondary and it would hesitate at first but then seemed to function normally (gps top speed 47 mph). I took the boat out this weekend to try some tuning to help the hesitation. It would barely get on plane and no matter when you opened the secondary it would lose power and bog down. I only had adjusted the idle mix at that point and i have since put it back where it started. I am considering purchasing the 1488 tuning kit in the hopes that more fuel flow will help but any advice is very welcome.

Ayuh,..... Did you thoroughly clean the entire fuel delivery system, Before you bolted on this new carb,..??
I ask, because it sounds like ya didn't, 'n just pumped more crap into the new carb,.....

Yer initial bog situation sounds like it just needed a bigger shot from the accelerator pump,....

 

[jhande]

Thank you for your response. The edelbrock has 2 metering rods i could be wrong but i thought the right rod metered the secondary fuel flow. When i first installed this carb( 1 week ago) i had hesitation and bog when the secondary opened under load. But the boat would plane in a reasonable amount of time with just the primary.
After on plane i could open the secondary and it would hesitate at first but then seemed to function normally (gps top speed 47 mph). I took the boat out this weekend to try some tuning to help the hesitation. It would barely get on plane and no matter when you opened the secondary it would lose power and bog down. I only had adjusted the idle mix at that point and i have since put it back where it started. I am considering purchasing the 1488 tuning kit in the hopes that more fuel flow will help but any advice is very welcome.

Okay, my bad! Edelbrock carbs are designed based off of a Q-jet. After a little research for trying to help you they did a few things different. So it's NOT just a rebranded Q-jet, it just uses similar technology with a twist.

Just curious... How did you know the problem was when the secondaries open? I mean, how did you know the secondaries were opening? Did you hear them? Did you see them opening? Vacuum secondaries open much slower and smoother than mechanical secondaries.

If that was the case it is possible the metering springs/rods/jets are the culprit. As engine vacuum drops the secondaries slowly open and the metering rods lift allowing more fuel flow.

Try a Google search for "How to tune an Edelbrock carburetor".
I quickly found this -

how to tune an edelbrock carburetor - Google Search

www.google.com

Again, make sure the ignition and fuel delivery systems are functioning properly before tuning the carb.

 

[Backyardmech]

Okay, my bad! Edelbrock carbs are designed based off of a Q-jet. After a little research for trying to help you they did a few things different. So it's NOT just a rebranded Q-jet, it just uses similar technology with a twist.

Just curious... How did you know the problem was when the secondaries open? I mean, how did you know the secondaries were opening? Did you hear them? Did you see them opening? Vacuum secondaries open much slower and smoother than mechanical secondaries.

If that was the case it is possible the metering springs/rods/jets are the culprit. As engine vacuum drops the secondaries slowly open and the metering rods lift allowing more fuel flow.

Try a Google search for "How to tune an Edelbrock carburetor".

Again, make sure the ignition and fuel delivery systems are functioning properly before tuning the carb.

 

[Backyardmech]

This carb has a mechanical linkage. I can actuate them by hand after removing the throttle linkage. When actuated there is a small squirt of fuel but i cant leave them open to see if fuel is flowing through the venturis. I might try removing the top to check the float bowls for debris. Although the canister fuel filter is new so the fuel "should" be clean.

 

[Lou C]

NO, the Edelbrock is simply an updated version of a square bore Carter 4bbl that was used on a lot of Mopars back in the old days.
Carter....Weber/Merc....Edelbrock....all closely related
The Quadrajet is different in that while it uses metering rods like the Edelbrock, it is a spread bore carb (more like a Carter Thermoquad) but the secondaries work differently. On the Quadrajet the secondary throttle plates are mechanically operated but the air doors above them are vacuum operated, they are held shut by an adjustable spring and are not supposed to open till the engine needs the extra air supply. This design eliminated the need for a secondary accelerator pump.
Holley 4bbls are different in that they do not use metering rods, marine units use vacuum secondaries though.

 

[Lou C]

Okay, my bad! Edelbrock carbs are designed based off of a Q-jet. After a little research for trying to help you they did a few things different. So it's NOT just a rebranded Q-jet, it just uses similar technology with a twist.

Just curious... How did you know the problem was when the secondaries open? I mean, how did you know the secondaries were opening? Did you hear them? Did you see them opening? Vacuum secondaries open much slower and smoother than mechanical secondaries.

If that was the case it is possible the metering springs/rods/jets are the culprit. As engine vacuum drops the secondaries slowly open and the metering rods lift allowing more fuel flow.

Try a Google search for "How to tune an Edelbrock carburetor".
I quickly found this -

how to tune an edelbrock carburetor - Google Search

www.google.com

Again, make sure the ignition and fuel delivery systems are functioning properly before tuning the carb.

nope completely different than a QJet
see above