carb issue

[cuda hunter]

Someone have an idea?

400 w/727.  Holley 3310 Vacuum secondary

When I push the gas pedal hard I get a sputter and the engine falls on itself.  I let off and feather it a little and she runs along.
When I get up to higher end on each gear I get sputtering. 
It was doing this worse when I first got her back on the road but I have tuned up the carb a bit. 

Is this an accelerator pump adjustment or a power valve? 

I know, "go get a vacuum reading on the intake". 

[Cuda Cody]

What color cam are you using?

[Chryco Psycho]

Could be play in the linkage , could be wrong cam or squirter size , could be the check ball is stuck from sitting , coul dbe a bad accel pump diaphragm , float level could be too low

[cuda hunter]

stock cam

float levels should be perfect
cam and squirter have been switched a few times.  Don't think it's either of those.
don't think it's check ball as I have had this problem for a while now.  However my memory doesn't even bring up a check ball.....

I have not changed the accelerator pump. 

I did switch to one size larger power valve. 

Do I need to  put down the cam specs and squirter sizes and power valve size to figure the answer out?

I don't mind throwing a little money at the carb so changing the accelerator pump is acceptable. 

[Arctoad]

I just finished rebuilding my 2300 carbs and I started from stock everything, jets, squirters, outboard diagram springs. I would definitely replace the accelerator diaphragm and be sure to clean the check ball.. If it boggs then likely to lean. There is a set-up in the manual to adjust your gap for the accelerator circuit, for Holleys.
Hold the throttle wide open and make sure a 1/16' drill shank can slide on the bottom of the linkage arm and adjuster screw, but you can't have excessive play.That'll get you started, give it a real good cleaning first if not already.
Good Luck 

[Chryco Psycho]

the power valve needs to 6.5 unless you have low vacuum where you need a lower rated power valve , not surre what you switched it to

[Cuda Cody]

What color cams have you tried?  Make sure your accelerator pump is working correctly too.

[Arctoad]

This is a great piece of information. Wondering if there is a chart for cfm vs lift? It has me thinking of the relationship between the inboard and outboard for a tri-carb set-up.. How much is needed for the Centre?
Sorry didn't mean to re-direct, maybe good for a separate topic.
Cheers

[Cudajason]

Someone have an idea?

400 w/727.  Holley 3310 Vacuum secondary

When I push the gas pedal hard I get a sputter and the engine falls on itself.  I let off and feather it a little and she runs along.
When I get up to higher end on each gear I get sputtering. 
It was doing this worse when I first got her back on the road but I have tuned up the carb a bit. 

Is this an accelerator pump adjustment or a power valve? 

I know, "go get a vacuum reading on the intake".

Starting point is to make sure everything is working properly!

Sounds like its going lean to me...not enough gas when you smash the go pedal!!

Using the chart Cody shared, I would pic a cam that adds more fuel lower in the curve them the one you are using and see what difference that makes...that should get you started in the right direction!



Jason

[Shane Kelley]

From the description it almost sounds like you have a fuel issue with the secondaries. If you drive it easy and just pull away from a stop sign does it do fine or does it it try to cough and sputter?

[Cuda Cody]

IMO, it's sounds like 2 different issues to me.  The first issues is when you try to "mash the gas hard" it stumbles going from the idle circuit to the run circuit.  That is almost always an issue with the air / fuel mix going lean or rich from the accelerate pump either from the wrong cam profile or an out of adjustment (or failing) pump.  An air leak will also mess up that transfer from the idle to the run circuit.

Once you make the jump from idle to run it works fine, right?

[70 Challenger Lover]

Not sure where the carb came from, whether it's new or used and been sitting on a shelf. If used and you aren't sure what changes have been made by others, you might consider breaking it down and checking a few things. I'd also put it back to original configuration first and then start dialing it's in. Before you remove it, I'd move the throttle by hand and make sure the accelerator pump arm is not binding or hitting something. I'd also look for a stream of fuel to show you the diaphragm is good and the cam is lined up right. From there, I'd consider a quick breakdown and inspection if you aren't sure what's inside. Easy enough to do and worth the effort.

By the way, I had a 3310 that did that exact thing and it turned out to be a metal burr on the accelerator pump arm. Most of the time it worked fine but then the arm would just stick until I pulled the carb off and tinkered with it. Annoying as hell. I've also seen the cam out of position so that it doesn't start shooting fuel immediately as it should. They have 2-3 holes so easy to make a mistake there.

The 3310 comes with a pink cam if I remember right and 72 primary jets. If the spring in the secondary diaphragm was changed to a much lighter spring, the secondaries open too quickly when you mash it and it will fall or at least bog significantly. If the spring is too heavy, the performance suffers but it shouldn't fall on its face or bog. I think the squirter sizes are 32. Obviously checking the accelerator pump diaphragm would be good also while it's apart.

Once you have done all that, test and change only one thing at a time testing each time in between. If it's worse or no help, change it back and try something different. As Chryco said, lot of things can cause something like that so you have to troubleshoot it. Eventually you start to see improvement and then you know you are onto something.

For example, if you have a big engine with heavy fuel needs, you might find that bigger shooters aren't enough because you run out of pump shot. So you Upgrade to the 50cc accelerator pump kit. Doing so means you need a little more clearance off the manifold so you get a bigger spacer. Then from there, you can play with bigger cams and bigger shooters. If things seem to be getting a little better each change, it tells you you are on the right track.

I know I'm gonna catch hell for saying it but I hate Holley carbs. I've had so many and they all seem very temperamental. I've had stuck floats, stuck accelerator pump arms, leaks, etc. I've gotten good at playing with them simply out of necessity. And when I switch to an edelbrock carb, I find it's a pleasure to dial in and I never have to mess with it again. I agree I will lose power by ditching the Holley but it's a trade off I'm okay with every time.

[Shane Kelley]

I'm no fan of "Holley" carbs either. They tend to be finicky and hit and miss on a good one. With that said I absolutely hate Edlebrocks! I really like the Quick Fuel carbs that are basically a massively improved Holley. Same design with all the needed corrections. They perform excellent right out of the box. Lots of ability to really micro tune if you are obsessed and looking for perfection. You don't have to but it's designed so you can. 

[70 Challenger Lover]

Good point. To be fair to the Holley design, I've never played around with other brands using the Holley design. Maybe if I did, my opinion would change. Edelbrocks always work for me but I also use them primarily in stock motors so it could be that using them in a higher performance motor would cause me to dislike them as well.

[JS29]

  I love my quick fuel!