Yellow Bullet Forums banner

1 - 20 of 28 Posts

·
Registered
Joined
·
557 Posts
Discussion Starter #1
Let's see if we can solve this...

Motor Specs
- 306
- e303 cam
- edelbrock e-street heads
- edelbrock performer rpm intake
- long tubes
- 18 degrees initial w/ 12 mechanical. Played w/ it a bit and no change.

This is in a 67' Mustang w/ a c4, 3.55 gears and 1800rpm converter

Carb is almost stock. 600 cfm street avenger.

66 Primary Jets changed to 68
PV is a 6.5
i went up a size w/ the squirter .028 to a .031 (i believe)
orange cam on 2nd hole

I have a wideband, but i have not drivin with it yet, i did set the idle to a 14.7 gas afr

again, the stumble happens w/ a light throttle and light load, i dont think it is the accelerator pump circuit because the stumble happens at cruise at 2300 rpm and below.

any suggestions.....
 

·
Banned
Joined
·
26,908 Posts
Vacuum secondary carb?? Try checking which spring is in the vacuum pod. Too light and it will pull the secondaries open when you dont need them.
 

·
Brewmaster
Joined
·
12,620 Posts
Never had luck with those avenger carbs. Personally, I wouldn't dial it in to a number on the wideband, dial it in on how it drives and use the wideband to see changes and possible problem areas. That being said, drive it now that you have it hooked up and see what's going on.
 

·
Registered
Joined
·
169 Posts
Had the same problem with a 670 street avenger.
The primary throttle blades ( transition slot ) had to be perfectly squared and the mixture screws richer than I liked to eliminated that transition lean stumble.
Had to use secondary throttle blades to set final curb idle.
I had better results with the green pump cam than a .035 squirter.
Shit canned it for a Quick fuel HR 680
 

·
Registered
Joined
·
784 Posts
Do the avengers have idle air screws? If they do, they might be turned in too far...
 

·
Registered
Joined
·
557 Posts
Discussion Starter #7
Had the same problem with a 670 street avenger.
The primary throttle blades ( transition slot ) had to be perfectly squared and the mixture screws richer than I liked to eliminated that transition lean stumble.
Had to use secondary throttle blades to set final curb idle.
I had better results with the green pump cam than a .035 squirter.
Shit canned it for a Quick fuel HR 680

that might be the route I take after a few more adjustments, question though.

- what do you mean by primary throttle blades perfectly squared?

- i'll try the green pump cam too, but I dont feel it is an accelerator pump issue.

I'm rebuilding a 57' belair now, just rebuilt the 670 street avenger that was on it, hope it is not that big of a PITA
 

·
Registered
Joined
·
33,118 Posts
Check to see if the mousetrap spring on the primary throttle shaft between the accelerator pump cam and the base plate is not so large in diameter it is preventing the accelerator pump arm from contacting the pump cam until after the throttle is open several degrees. The last one of those fluster clucks I ran into was just a week ago and it required a blue pump cam and some bending of the pump arm to get the pump arm to sit on the cam at idle so it would pump immediately with the slightest movement of opening the throttle off-idle.

#68 is a fairly large jet for that venturi size. #65 is more commonly the happy jet, however each engine has its own appetite.

Ladies and gentlemen at Holley, if you read this, fix this problem of the primary throttle shaft spring being too large. This has been a problem for 15-20 years and it's getting old. Do any of you people ever drive one of the carbs you build back and forth to work every day for a month? Obviously not, this spring problem has gone on for years. :confused:
 

·
Registered
Joined
·
8,489 Posts
65 sounds like a pretty big power valve. I'd try a 35 and see what happens.
 

·
"Shocks don't matter"
Joined
·
21,585 Posts
65 sounds like a pretty big power valve. I'd try a 35 and see what happens.
Stumble aint always a lean condition, I agree. Most likely manifold vacuum is low at light throttle or idle (performance parts listed), although admittedly, I know nothing about the camshaft mentioned in the engine specs list. High probability 3.5 - 4.5 power valve would be in it, if it were me. Agreed.
 

·
pist'n Broke
Joined
·
20,943 Posts
Let's see if we can solve this...

Motor Specs
- 306
- e303 cam
- edelbrock e-street heads
- edelbrock performer rpm intake
- long tubes
- 18 degrees initial w/ 12 mechanical. Played w/ it a bit and no change.

This is in a 67' Mustang w/ a c4, 3.55 gears and 1800rpm converter

Carb is almost stock. 600 cfm street avenger.

66 Primary Jets changed to 68
PV is a 6.5
i went up a size w/ the squirter .028 to a .031 (i believe)
orange cam on 2nd hole

I have a wideband, but i have not drivin with it yet, i did set the idle to a 14.7 gas afr

again, the stumble happens w/ a light throttle and light load, i dont think it is the accelerator pump circuit because the stumble happens at cruise at 2300 rpm and below.

any suggestions.....
I would try the white pump cam,most come stock with them, and try all hole positions...it will make very big differences just with the cams... also if you can use a squirter between what you changed... have you checked the float level? Maybe up the jet size.. also the accelerator pump spring, too tight or to lose ?

Pull baseplate and check the transition passage isn't blocked. How lean is it when it stumbles?
^^ now that this was mentioned, have you checked the plugs for lean or richness??
Mortec.com has a nice Holley tuning trick section, I have used it to tune Holley
 

·
Registered
Joined
·
6,716 Posts
bigger squirters
 

·
Registered
Joined
·
33,118 Posts
Did you look to see if the accelerator pump lever is actually touching the pump cam and not held off the cam until about 1/4 throttle?

There is a 90% probability the pump will not squirt at all until the throttle is quite a ways open because the spring on the throttle shaft is too large and holds the pump lever up and off the cam.
 

·
Registered
Joined
·
2,297 Posts
Never had luck with those avenger carbs. Personally, I wouldn't dial it in to a number on the wideband, dial it in on how it drives and use the wideband to see changes and possible problem areas. That being said, drive it now that you have it hooked up and see what's going on.
This ^^^
Try adjusting the idle mixture screws to get it to run a little richer at idle.
 

·
Registered
Joined
·
9,107 Posts
i know somebody on here will get ya fixed up. But my advice is throw that street avenger in the fuckin trash. Never had any luck with them and im not alone on that one
 
1 - 20 of 28 Posts
Top