Carburator frustration

[Scott06]

Here's the link to the Edlbrock tuning guide https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/carb-tuning-guide.pdf If you havent worth reading the first section on how the carb works. you need to determine if your issue is with WOT or part throttle cruise as that will lead you to where to go on the tuning chart

The step up rods are only on the primarys, while the secondaries you have to pop the top off and change secondary jets. I think start to get into my secondaries around 3800 rpm at a steady state cruise.

Per Bondos comments - I had a stumble off idle but no issues getting on plane, I did go up in accelrator pump nozzle, you also can adjust the volume of pup shot on the pump arm positioning.

What rpm are you seeing the bog, did it get on plane ok with the old carb?

 

[jhande]

nope completely different than a QJet
see above

Thanks for the info.
I've really only been a GM mechanic with an occasional Ford. Never messed with Mopar.

After the little research I did noticed it wasn't exactly like a Q-jet other than it incorporated similar metering rods (kind of).

 

[Scott06]

Thanks for the info.
I've really only been a GM mechanic with an occasional Ford. Never messed with Mopar.

After the little research I did noticed it wasn't exactly like a Q-jet other than it incorporated similar metering rods (kind of).

Plenty of GM cars back in the day used them. Mid 60's pontiacs used them until the Q-jet came out. The metering rods are nice for tunability and the secondaries are essentially vacum operated as the air valve is weighted and only opens based off what the engine needs much like the q -jet, just gets there in a different manner.

 

[Backyardmech]

Here's the link to the Edlbrock tuning guide https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/carb-tuning-guide.pdf If you havent worth reading the first section on how the carb works. you need to determine if your issue is with WOT or part throttle cruise as that will lead you to where to go on the tuning chart

The step up rods are only on the primarys, while the secondaries you have to pop the top off and change secondary jets. I think start to get into my secondaries around 3800 rpm at a steady state cruise.

Per Bondos comments - I had a stumble off idle but no issues getting on plane, I did go up in accelrator pump nozzle, you also can adjust the volume of pup shot on the pump arm positioning.

What rpm are you seeing the bog, did it get on plane ok with the old carb?

It got on plane fine with the old 2 barrel but it would lose power and backfire at anything but wot. Not sure of the rpm, tach doesnt work, but it cant be over 2500 rpm

 

[Backyardmech]

And thank you Scott06. I was trying to find info on the secondary fuel circuit everywhere.

 

[Lou C]

Perhaps Carter's finest moment with Chrysler was when 2 of them sat atop a cross ram manifold for a 413 Wedge or 426 Wedge and later on the 426 Hemi.

 

[jhande]

Plenty of GM cars back in the day used them. Mid 60's pontiacs used them until the Q-jet came out. The metering rods are nice for tunability and the secondaries are essentially vacum operated as the air valve is weighted and only opens based off what the engine needs much like the q -jet, just gets there in a different manner.

Thanks Scott.
Mid 60's were just a bit before my time turning wrenches.

 

[Scott06]

It got on plane fine with the old 2 barrel but it would lose power and backfire at anything but wot. Not sure of the rpm, tach doesnt work, but it cant be over 2500 rpm

Given this comment re the old carb Id still be suspicous of fuel starvation. If it is just a stumble off idle to 2500 rpm and then it recovers Bondo is likely right that it is the accelrator pump . You can try moving the hole the pump rod is in to the closest on on the pump arm this should oincrease the pump shot volume. As mentioned I put a bigger nozzle in.

What do your spark plugs look like

 

[Backyardmech]

I havent pulled the plugs yet. Just took the carb off to bench test it. I filled it with fuel with a funnel and hose. Should there be a fuel squirt when the secondaries are activated? I disconnected the choke linkage and actuated the throttle linkage and no fuel was delivered to the secondaries.

 

[Backyardmech]

that posted weird

 

[jhande]

The secondaries function off of vacuum. You might be able to get a shot of fuel from the accelerator pump but not sure. Other than that you won't see fuel.

I would carefully remove the top plate and inspect for any crap that might have gotten sucked in.

Then reinstall the carb and follow the advice everyone has been giving you, especially the "How to tune carb".

 

[Backyardmech]

I sprayed carb cleaner thru all 4 of the fuel ports in the float bowls and checked the float adjustment and reassembled and reinstalled the carb. I observed a noticeable increase in fuel delivery to the secondaries while running at the dock. It still bogs a bit when the secondaries open and requires full down tilt to get on plane but it is very much improved. I am ordering a larger accelerator pump and nozzle. I think that will solve the remaining issues.

 

[Scott06]

when advancing the throttle on a carb with gas that is off the engine the only thing that will squirt gas in is the accelerator pump which is on the primary side only. Fuel will only come out out of the veturis when air is moving through them to create a pressure drop.

you seem overly focused on the secondaries, below 2500 rpm they aren't open and pulling air yet. You can have the throttle wide open but the air valve over the secondaries gets pulled open via airflow That the engine requires.

 

[Scott06]

I sprayed carb cleaner thru all 4 of the fuel ports in the float bowls and checked the float adjustment and reassembled and reinstalled the carb. I observed a noticeable increase in fuel delivery to the secondaries while running at the dock. It still bogs a bit when the secondaries open and requires full down tilt to get on plane but it is very much improved. I am ordering a larger accelerator pump and nozzle. I think that will solve the remaining issues.

How did you observe a noticeable increase in fuel delivery from the secondaries at the dock?
when you think the secondaries open what rpm? You were thinking these issues were at or 2500 or less. At 2500rpm a 5.0will need 187 cfm , the secondary air valve isnt opening yet. You will hear the engine noise change when it does.
what do the spark plugs look like theywill tell u a lot about the mixture if you read them