Hesitation/bogging street avenger

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jcarr210

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I have a 670 street avenger on my 340 with a lunati cam that’s giving me issues. I had some problems with it and turned out something was clogged in the discharge nozzle. That’s fixed and the car has a rough idle from the cam but otherwise perfect. It doesn’t die after revving it coming to a stop or anything.

Problem is if i step on it it will bog down and either die or sounds like it’s dead then hauls *** off. I almost have to feather it to get it going before I can give it more gas. Once I’m accelerating everything is fine and it cruises all day long. If I barely touch the pedal it accelerates slowly and gives me no issues. It ran perfect before I replaced the intake manifold gasket and now it’s giving me issues. I adjusted the accelerator arm and it didn’t make a difference. I’m not too savvy when it comes to carbs so any advice would be appreciated. Thanks!
 
I checked for vacuum leaks and even sprayed some starting fluid around any possible bac and no dice. I’ve added a video.
 
What are the specs on your cam? The 276* Voodoo needs initial timing around 16*. Max about 34*
Set your idle in drive for about 850 rpm. Check your carb squirters that they shoot right as the throttle is cracked open.
 
340fourspeedDuster said:
What are the specs on your cam? The 276* Voodoo needs initial timing around 16*. Max about 34*
Set your idle in drive for about 850 rpm. Check your carb squirters that they shoot right as the throttle is cracked open.
Click to expand...


It’s the Advertised Duration 268/276, Lift .494/.513 cam. It’s on a 340 with aluminum heads and air gap manifold. I want to say it has 18* initial but last time I checked was well over a year ago. I’ll check that out and mess with the idle a bit while I’m there.

Turns out the squirter to the right was barely squirting so I got that cleaned out but still doesn’t look like the pattern coming out of the left side. I’m wondering if there’s crap in the carb that got knocked loose when I took it off to change the intake gasket.
 
I'm gonna say it's a little of this and a little of that.
First;make sure your PCV is hooked up and working, and that the pan is not overfilled.Then unhook your Vacuum advance, and cap the carb-port, until you get this sorted.
Next,you have to prove several things and in the right order. I listed these in the order I would go hunting;
Engine temperature,Fuel level, Squirter discharge pattern, valley Vacuum leak, PV cut in and operation,Transfer port sync.
The T-port sync will pretty much set the timing for you, IF; the fuel level is correct,there is no manifold vacuum leak, and if the PV is operating correctly. That's why I listed it last today.

Judging from the way your car cranks, I'd guess;too-much timing or a hot engine,perhaps both
Judging by how it fires up, I'd guess: the fuel level may be too high, the T-port sync is off, or the PV is late to shut off, which could be calibration or unusually low manifold vacuum..
The lazy throttle response points to the accelerator pump, the T-port sync, and the PV.
The high idle may be the band-air required to overcome all the other issues.

If this is a fresh rebuild, you gotta keep it cool for quite a few miles, until things relax inside. In the beginning every time you shut it off, things swell up inside there, and try to stall the starter. If you can't let it idle cuz it wants to overheat, FIX the cooling system before you do anything else.
That's the best I got, good luck.
 
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If you're sure you've got the timing sorted out, the pump shot adjusted correctly, and no other glaring issues like a vacuum leak or anything, I'd say you've got some tuning to do on the carb. Those street avenger carbs are tuned way lean from the factory. They have tiny idle feed restrictors that are undersized for hot rod motors with a decent sized camshaft. I tried quite a few things trying to tune the 670SA on my 340. Using a wideband gauge to monitor the AFRs, it was pretty apparent that the idle circuit was way lean, leading to a persistant stumble on acceleration. If you're committed to using that carb, you can try a few things. Try a larger accelerator pump cam and larger squirter. You can also richen up the idle by turning out the idle mixture screws a bit. You can even raise the float levels and increase fuel pressure a tad if you've got an adjustable regulator. These are all pretty much bandaids for an idle circuit that's way too lean. If you're brave enough, drilling and tapping the IABs for a larger size would be ideal. I went through this exact thing on my 670. I ended up going with a double pumper couldn't be happier.
 
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