Second brand new Holley carb flooding?

[AJ/FormS]

Hi thanks for the replays. This is the third new carb. The first new carb was a 670 Holley street avenger. It worked great and never flooded. The problem was that it stumbled at take off and I couldn't get it to stop so I sent it back and got the 750 double pump. Both the 750s that have flooded seem to have started it after letting off the gas and the motor winding down. The gas is coming out of the front lil tube that sticks up. I adjusted the float level and looked at the needle of the first 750 and it didn't help. The only reason I went with Holley is that say these things are tested before shipped and ready to bolt on at go. If I can't get get figured out I will never buy another Holley.

Well before you write Holley off, Pay attention to the guys here.

You say "started it after letting off the gas and the motor winding down. The gas is coming out of the front lil tube that sticks up." So I just gotta say; This sounds like fuel slosh to me.
Four-speed cars with plenty of compression, during compression braking at higher rpms can decelerate so hard that the fuel can slosh to the front of the bowl. When this happens the float can fall into the void, and more fuel comes in. Now the bowl has too much fuel in it. Then when you get back on it, the fuel moves to the back, and up the spout.
Now with an automatic, this is less likely to happen, but if you are manually downshifting, it still could.
This is not flooding. The engine may even continue to run pretty good, until the sloshed fuel spills into the carb throats,upon getting back on it.
So if you are driving like this, your bowls may need baffling and/or the float level changed for your style, or just quit doing that, or install a dashpot on the linkage so the butterflies cannot slam shut, or open the butterflies some.
If you are running a lot of idle timing,the butterflies may be too far closed, and that would contribute to the slosh idea. I mention this because from the description of the "bog" with the first carb,(and the possible faulty T-port sync) this seems very likely.
In all honesty and fairness to Holley, 3 faulty carbs in a row seems like incredibly bad luck.

 

[72bluNblu]

The issue with the street avenger might not be related at all.

I tried two street avengers on my 340, a 670 and a 770, both brand new. I could never get them tuned correctly to get rid of a lean spot (and stumble) at the primary to secondary transition. They would work great everywhere else, but under hard acceleration the car would go lean long enough for the engine to stumble before the secondaries kicked in. That was indicated with an A/F gauge. I changed everything, secondary springs, pump shot nozzles and cams, even jet sizes. Street Avengers are vacuum secondary carbs though, and I was never able to get the secondaries to be fast enough. I could flood it with the pump shot using a fast pump cam and large nozzle, but since the street avengers only have a single accelerator pump that hurt driving it the rest of the time. When I changed the springs I could get it to bring in the secondaries too hard after the lean spot, but not get rid of it. And that also caused the secondaries to come in under higher load situations, like pulling a long grade.

I swapped to a 750 DP and solved the issue completely. But that was with my 340, which puts out around 400 hp, and a 4 speed. After some searching I found that there's more than a few folks with 4 speeds that had the same issue, but folks with automatics didn't. With the hot 340 and 4 speed the mechanical secondaries worked better and the second accelerator pump took care of the big fuel demand going into the secondaries without ruining the primary shot. Just needed a carb with more adjustability to match the engine.

Well before you write Holley off, Pay attention to the guys here.

You say "started it after letting off the gas and the motor winding down. The gas is coming out of the front lil tube that sticks up." So I just gotta say; This sounds like fuel slosh to me.
Four-speed cars with plenty of compression, during compression braking at higher rpms can decelerate so hard that the fuel can slosh to the front of the bowl. When this happens the float can fall into the void, and more fuel comes in. Now the bowl has too much fuel in it. Then when you get back on it, the fuel moves to the back, and up the spout.
Now with an automatic, this is less likely to happen, but if you are manually downshifting, it still could.
This is not flooding. The engine may even continue to run pretty good, until the sloshed fuel spills into the carb throats,upon getting back on it.
So if you are driving like this, your bowls may need baffling and/or the float level changed for your style, or just quit doing that, or install a dashpot on the linkage so the butterflies cannot slam shut, or open the butterflies some.
If you are running a lot of idle timing,the butterflies may be too far closed, and that would contribute to the slosh idea. I mention this because from the description of the "bog" with the first carb,(and the possible faulty T-port sync) this seems very likely.
In all honesty and fairness to Holley, 3 faulty carbs in a row seems like incredibly bad luck.

Totally agree. My 340 can engine brake hard enough that I can see the results of the fuel slosh on my A/F gauge, especially in 1st and 2nd gear. It doesn't usually cause any fuel spill or engine bog with just compression braking, but it does make a difference. And on that note, I only run 3.55 gears out back with 26" tall tires. A set of 3.91's would make the issue worse.

I've gotten on the brakes hard enough though that I've had to pedal the thing to keep it running though, and that was definitely fuel sloshing in the bowls. Disadvantages to having 13" rotors and soft tread compounds I guess.

Baffled float bowls? Ever done it A/J? I'm curious. Might come in handy during an autoX.

 

[AJ/FormS]

Baffled float bowls? Ever done it A/J? I'm curious. Might come in handy during an autoX.

I threw that comment in there to emphasize the idea. I debated with myself whether or not to leave it in, but I'm glad I did. Until the OP returns and validates(or not) as to his driving style, and the slosh theory, this question was never to come up.Afterall there were 4 better solutions there.

But, no, you, O clever-one, spotted the RedHerring;and almost instantly, I might add.

You can, baffle it, but with street tires,etc this is seldom an issue. IIRC I have seen brown plastic baffles in some Holley somewhere/sometime; 1850s I think. And a metal one in a TQ I think, and I seem to recall one formed from open-cell foam.And then there's the Holley slosh tubes.The Holley 4150s with side hung floats are a good solution, for straightliners.The Qjets bowl is really tiny, but I'm pretty sure I have seen white plastic baffles in there too.Yeah pretty sure.
The slosh can be contained in a jumper tube, as previously posted.But the rich running after-effect can be a significant issue. You will be more clever than I to solve it.
My experience in this is banging through farmers fields, and jumping it off little berms, on my way to the finish line, of a Rally-Cross. Absolutely the number one funnest experiences I have ever had. Who cares about winning (actually I was mere seconds from the trophy)! Who cares about surviving, (at least half of the entrants broke in round one)! Who cares how pretty your car is, or not(mine was easily the prettiest-no contest)!Who cares how quickly the track deteriorates to ruts, bump, and mud,(it just puts more fun into it)!
Naw, it was the thrill of participating! :
And the crowd goes wild,as his car returns to earth, and his oilpan flings up dirt and the clods are catapulted into the stands! And is he on fire?! No!, it's just oil burning off somewhere.What a show,what a thrill, what a time we had!
Meanwhile, back in the pits; Remove the evacuators, check the pan, saddle up it's go-time again. I am thoroughly convinced that I would have taken the trophy home that day, by way of attrition. Just one more round....It was just HIM and me and a couple of sorry looking survivors.
Helabigfun!
I drove 35 minutes there, and I drove 35 minutes back. A couple of days later I brazed up my oilpan,and checked my alignment (it was bang-on), and fabricated a bellypan. Then it was business as usual.