any holley avenger gurus out there?

[colonel mustard]

so first here are the specs im working with

350 sbc
15* ptdc
mild cam
holley avenger offroad carb
edelbrock intake

my old edelbrock carb finally crapped out and I swapped in a Holley offroad carb 670. start up great, idles great. slowly accelerates great. buy my off idle accelerating has stumbles...almost like it is missing. the Holley currently has the red accelerator pump cam and is on number 2 setting. I idle at around 750-800 RPM. im thinking I will change that setting to the number one postion and see if it helps.

whats yalls thoughts? I didn't have this stumble with the edelbrock, so I know it is fuel related.

change pump cam size?
change accel pump nozzle?

any thoughts would be great...
thanks

 

[dvdswan]

Read this...

https://ck5.com/forums/threads/holley-truck-avenger-tuning-tips-and-review.174116/

 

[bucket]

I ran one on a similar combo. I don't remember what pump cam I used, but I did use a #35 squirter.

 

[bft305]

I followed the ck5 article above and went with the blue pump cam on #2 and a #35 squirter. I still had some issues with stumble. I discovered that the accelerator pump metal lever under the screw with the red spring (sorry I don’t know the real term for it) it had to much pressure on it. I backed off the spring all the way and it still had too much pressure on it. This was causing the accelerator pump to always be engaged and too much fuel was causing my stumble. I bent that down a little and it helped a lot. I still have a tiny bit of stumble if I stab the throttle but it is much better. I have not rejetted the secondaries yet. My transmission gave out so now I am more focused on that instead of making the Holley TA perfect.

 

[Rusty Nail]

I forward the motion that you have been trying to tune transmission problems out of your carburetor. ?

Just a thought.

 

[potent rodent]

hey all im new here , was reading the problem with the 670 carb , first off what engine do u have is it stock or mild ,first off run cam on number 1 setting then set your acc pump arm so it has 10 to 15 thou between pump arm and acc pump itself u should be fine with the squirters it came with good luck

 

[bft305]

I forward the motion that you have been trying to tune transmission problems out of your carburetor. ?

Just a thought.

The OP doesn’t have transmission problems, I was just sharing what I did with my carb. Then mentioned I have not perfected my carb settings, since my transmission gave out so I am focused on repairing that. Sorry for the confusion!

 

[Turbo4whl]

I followed the ck5 article above and went with the blue pump cam on #2 and a #35 squirter. I still had some issues with stumble. I discovered that the accelerator pump metal lever under the screw with the red spring (sorry I don’t know the real term for it) it had to much pressure on it. I backed off the spring all the way and it still had too much pressure on it. This was causing the accelerator pump to always be engaged and too much fuel was causing my stumble. I bent that down a little and it helped a lot. I still have a tiny bit of stumble if I stab the throttle but it is much better. I have not rejetted the secondaries yet. My transmission gave out so now I am more focused on that instead of making the Holley TA perfect.

The accelerator pump should always be engaged.

I believe you may be miss interpreting what the accelerator pump does. As you move the throttle open the accelerator pump moves too. It only squirts fuel as you move the throttle.

When driving and throttle up, more air moves in. The main jets take a moment to respond to the increased air flow. This new airflow would be too lean. So the accelerator pump squirts some fuel into the new additional airflow.

So from idle to full throttle, where ever you start from, increasing the throttle, the accelerator pump should squirt more fuel. This is what the different plastic cams are for. To make sure in your application, the accelerator pump has the proper travel.

Holley's with fixed sized jets, sometimes need more fuel than they supply. This is what the power valve is there to do. Power valves also are available in different flows.

 

[bft305]

The accelerator pump should always be engaged.

I believe you may be miss interpreting what the accelerator pump does. As you move the throttle open the accelerator pump moves too. It only squirts fuel as you move the throttle.

When driving and throttle up, more air moves in. The main jets take a moment to respond to the increased air flow. This new airflow would be too lean. So the accelerator pump squirts some fuel into the new additional airflow.

So from idle to full throttle, where ever you start from, increasing the throttle, the accelerator pump should squirt more fuel. This is what the different plastic cams are for. To make sure in your application, the accelerator pump has the proper travel.

Holley's with fixed sized jets, sometimes need more fuel than they supply. This is what the power valve is there to do. Power valves also are available in different flows.

I do understand about the accelerator pump, but I guess I didn’t explain myself well. I didn’t bend the arm till it was not touching the acc pump. Even with my adjustment screw all the way off there was not 10 to 15 thou from the acc pump as per Holley’s instructions. (I am not at home right now so I forgot the correct specs, thanks potent rodent!). Yes I probably could have went from the #2 position to #1 but I guess at the time I didn’t think about that and was following the ck5 article. Anyways, I will admit I don’t know everything about carbs that is for sure and thanks for the information!

 

[potent rodent]

as soon as u open the throttle there should be gas coming out of the squirters if not u are going to get a stumble due to going lean , thats why i said make sure your acc pump is set, the arm should just touch the pump

 

[broketiredugly]

then there is a timing issue. if timing is slow, you will stumble on quick hit, but run okay at slow hit.

 

[MikeB]

With a mild cam, that Holley carb should be in the ballpark right out of the box, except for maybe the float level.

Here's something people don't always realize: If your Edelbrock manifold is spread bore, you will need a "sealing plate" and gasket like Edelbrock #2732. This will prevent small vacuum leaks at the rear base of a Holley square bore carb. These leaks can be very slight, but will drive you nuts.

https://www.summitracing.com/parts/...MIttLMgpLn6AIVqf_jBx1-SAYIEAAYASAAEgL43_D_BwE

You must be registered for see images attach

 

[Rusty Nail]

Very nice addition Mike.

 

[Havasublue]

My two cents...
Get rid of that carb!
I talked to Holley guys for hours and hours! YOU WILL NEVER GET CRISP OFF THE LINE ACCELERATION WITH THAT CARB!
Get the Summit 570 cfm carb and a jet kit.
Don't forget the fuel transfer slot.
Curve the distributor right!
We all think we have more motor than we really do. You need a built striker motor to use that much fuel. Distributors are always curved wrong !
Timing light with dial back and a vacuum gauge.
Lightest springs in the distributor, small adjustments at operating temp. Manifold vacuum for advance. You should be about 14-16 degrees off idle. All in about 3000 rpm

 

[bucket]

My two cents...
Get rid of that carb!
I talked to Holley guys for hours and hours! YOU WILL NEVER GET CRISP OFF THE LINE ACCELERATION WITH THAT CARB!
Get the Summit 570 cfm carb and a jet kit.
Don't forget the fuel transfer slot.
Curve the distributor right!
We all think we have more motor than we really do. You need a built striker motor to use that much fuel. Distributors are always curved wrong !
Timing light with dial back and a vacuum gauge.
Lightest springs in the distributor, small adjustments at operating temp. Manifold vacuum for advance. You should be about 14-16 degrees off idle. All in about 3000 rpm

I strongly disagree, I had superb throttle response. 670 TA, on a basic 350 with mild cam. It was rather easy to accomplish. Iirc, the earlier-1 carbs were problematic, but I had a -3.