Street Demon vs AVS2

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qkcuda

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I am thinking about my next build which will be an economy/performance 383 hopefully for a first generation Charger. The cam will likely be in the 210-220 range with low end torque more important than high end horsepower. I want a comfortable cruiser, that will get decent mileage cruising, with say a 2.94 gear, or possibly an overdrive. I like the looks of the 625 Street Demon with the composite body. It has small 1 3/8 primaries and the single large secondary blade. I have read good reviews on them. lately I have also been reading a lot of good things about the new 650 AVS2 with annular discharge boosters (the SD has conventional boosters). It also has slightly smaller primaries than secondaries. Any thoughts or real world experience with either?
 
I had a street demon 625 on my 360 magnum. I loved it and never had a single issue with it. I sold it when I put my 408 in and bought the street demon 750. The 625 was a composite body, I intended to get the 750 in composite but ordered wrong and got the aluminum.

The ONLY negative remark I have with them is that you have to remove the carb and flip it upside down to access the screws for a jet change. It looks really nice and slick not having any screws visible when installed, but it's no fun making jet changes.
 
That's not a big issue. I hope not to have to mess much with the jetting, and I found it easier to remove my holley every time I changed jets anyway.
 
I put a 650 AVS2 on my 340 this spring and am very happy with it. Adjusted the idle screws and it runs very well. Has a slight hesitation on an aggressive tip in but I'm holding off going nuts on a tuneup until I address some other issues. Drives great, starts and idles great. I got the electric choke version.
 
I have the 625 SD on my 75 F250. 351M, BW T-18 4 speed, Dana 60 with 3.73 gears. It's a big *** truck and will haul *** for what it is. I can make it get decent mileage if I just use my big toe on the gas pedal. It'll bump 20 as long as I keep it at 55 and no faster.....which is a tick over 2100 RPM. Any faster and the mileage suffers exponentially. It's pretty humorous, actually. In 5MPH, from 55 to 60, you can start to watch the gas needle move. But that's not the carburetor, that's just the physics of the truck and gears.

All that said, from what I've read about the AVS, you'd probably be splittin hairs to find a real performance difference between the two carburetors. Just pick one. You're not gonna miss out on anything.
 
Running a 750 demon on a 230° cammed 360 and only had to adjust the mixture screws, damn good carb.
 
Another question. I always had issues with Carter/Edelbrock aluminum carbs with heat soak and fuel evaporation. That is why I thought the composite body on the Demon might be better. Anybody else have issues?
 
Another question. I always had issues with Carter/Edelbrock aluminum carbs with heat soak and fuel evaporation. That is why I thought the composite body on the Demon might be better. Anybody else have issues?
Eddelbrock throttle shafts wear out quickly also and yes i hate the gas evaporation problem.
 
Another question. I always had issues with Carter/Edelbrock aluminum carbs with heat soak and fuel evaporation. That is why I thought the composite body on the Demon might be better. Anybody else have issues?

Mine is the all aluminum body. No issues with that and in Georgia's HOT and HUMID summers. I also run the THICK and CORRECT base plate gasket. It's somethin like .320" thick.
 
I have the AVS2 500 cfm on my 273. Installed on the recommend insulating gasket and after a small tuning change the tune is most excellent. Solid from idle to WOT.
 
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I have the AVS2 500 cfm on my 273. Installed on the recommend insulting gasket and after a small tuning change the tune is most excellent. Solid from idle to WOT.

Did everything around the gasket get its feelings hurt?
 
Did everything around the gasket get its feelings hurt?
Not that I am aware of. It's the Edelbrock part numbered gasket recommend by them. I'm running an aluminum 1\2" spacer with gasket on the LD4B then the insulating gasket then the carburetor.
 
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Not that I am aware of. It's the Edelbrock part numbered gasket recommend by them. I'm running an aluminum 1\2" spacer with gasket on the LD4B then the insulting gasket then the carburetor.

I think your gasket needs sensitivity classes. Or maybe you should get an insulating gasket. :lol:
 
I've got the 650 AVS2 on my 340 4spd car.
Bought it after having some problems with the original AVS, and got the one with the electric choke. I use the edelbrock insulating gasket also.
Best carb, right out of the box, I've ever owned!
Hooked up the choke, adjusted the idle, and done.
Starts immediately. No hesitation at any speed or rpm. Runs perfect .

20190625_144256.jpg
 
I've ran a couple of AFB and AVS, and I greatly prefer the Street Demon I'm currently running on my Dart. Since I've been running it, I have convinced several other local guys to switch over to the SD and they all love them! For an entry level carb that works well all around, you can't beat it.
 
i got a avs 500cfm on my slant six no complaints at all bolt on and go, no bog nothing.
 
Another question. I always had issues with Carter/Edelbrock aluminum carbs with heat soak and fuel evaporation. That is why I thought the composite body on the Demon might be better. Anybody else have issues?
I ran a 750 composite body Street Demon on what has to be the biggest oven of an engine compartment, an A100 van with the engine under a dog house where heat soak can be intense. I always lifted the cover after shut down to vent, but the heat was still radiating and soaking into everything. Never ever had a problem running, during stop and go traffic, or restarts shortly after shutdown. No fuel percolating from the boosters or accelerator discharge nozzles. Running a 750 DP now for other reasons, but the Street Demon works great. Excellent throttle response and power. Only had a linkage issue (ford kickdown contraption on throttle was causing some binding, I cut it off problem solved) and the choke flap on my sons 625 kept sticking closed in the tower, hyper extending for some reason. Put a small washer under a nut on the carb stud to act as a stop for the flap. Problem solved. Not sure if its a common issue with them. Its affordable. But performs nonetheless
 
I am encouraged by all of the positive comments both ways. I am leaning towards the Street Demon for 2 reasons, the smaller primaries and the composite body and the potential heat soak issues. I was originally thinking about fuel injection, but budgetary limitations and some recent negative feedback, led me back to finding a simple carb that will work. Now I just need to find a car to slide under it.
 
I am encouraged by all of the positive comments both ways. I am leaning towards the Street Demon for 2 reasons, the smaller primaries and the composite body and the potential heat soak issues. I was originally thinking about fuel injection, but budgetary limitations and some recent negative feedback, led me back to finding a simple carb that will work. Now I just need to find a car to slide under it.
A carb will run for years and it's easy to maintain, efi if something goes wrong your on a flatbed and waiting for parts.
 
Yes, one of my goals is to drive it to Carlisle, which is about a 7-8 hour trip for me. That is why mileage and reliability factor into the equation.
 
With the 2.94 rear gears; 65 mph is about 2400 rpm. with a cam in your range and decent compression, pretty much any carb will do, on account of the venturies will have plenty of airflow, pushing that first-gen Charger thru the air.
I doubt if fancy boosters or small primaries will offer a significant difference. If you already had a carb in the 700 to 850 range, I would just bolt that on and go, cuz you can buy a lotta lotta gas for what a new carb will cost you. And that money would pay for any mileage difference for possibly several years. And in the mean time, you'd have a ripper of a 383.
As for the overdrive, if a GVod (.78); it could be decades before it pays for itself in fuel mileage savings alone. And I wonder if you can run it with 2.94s at 65 mph and a 220* cam. The Rs would be 1850ish, and the typical 220 cam is likely still in reversion down there.
The A500/518 overdrive ratio (.69) is even worse bringing your hiway rpm down to; 65=1640, with 2.94s; . And even the typical 210 cam with that short stroke 383, is likely pumping aircharge backwards.

But if you have to buy a carb no matter what;
Then I like your idea of a small triple-booster primary, HUGE rear dump, insulated bowl, and ...... wait;
echos of yesteryear and the 850 ThermoQuad. If you get get your cylinder pressure up closer to the detonation zone, but not into it, then that idea will be dynomite.
But the 2.94s plus overdrive idea, with a lazy-ramp 220 cam,I'm not buying it... unless 65 is not yur cruising speed. At 80mph for instance, the 2.94s with a TF-od makes about 2000 rpm in lock-up, so with a small triple-booster primary, I can see that playing nice with a fast-rate short-ramp 220 cam, but just barely.

I tell you what; I like that 220 cam, it's almost perfect for a streeter, especially a heavy first-gen Charger. What it needs is an A500 with it's 12%lower first gear equal to 12% more rear gear. And if you upgear to 3.23s, you will have a dynomite starter gear of 8.85 and still cruise at 75=2100 in loc-up, now yur talking performance, with economy.
Two things are must haves; a limited slip rear, and computerized timing, cuz to get to the mpgs at 2100, the engine will likely never get the timing it wants, to pull the big mpg numbers. I'll guess she'll like 56 or more degrees at 2100. And even if you could force 34* of all-in timing on her at 2100, and somehow keep her out of detonation,and you modded your Vcan to get another 22* out of her, now totaling 56*@2100, what happens when you floor it?
Yeah what happens with that 3.23rear?
With iron heads;
I can only tell you what has to happen, and they are all simultaneously and instantly;
The Vcan has to drop to zero-advance, to prevent detonation. This is only possible with a lot of throttle opening.
Because of that, the secondaries have to come in a lil later.
The loc-up has to kick out, to prepare for;
The trans has to kick down to a gear that provides at least 3600rpm., to deal with that 34* all-in timing.
The carb has to get fresh cold air and she has to go slightly rich, so the plugs can cool off in a hurry, cuz running lean, they will be hot. If you run a cooler plug, they will likely foul around town.
With iron heads, a stand-alone timing computer is pretty much mandatory for getting the big-number mpgs, so you can better set and control; the power-timing, the idle-timing the PartThrottle timing and the cruise-timing.
Course if your compression ratio is down in the basement, then some of these problems go away. But low-compression and big-number mpgs with a 220 cam should never be said in the same breath.
Ok but that 383, at 3600 rpm, at WOT, and 80% VE is calling for 320 cfm. Which is likely more than the 650 Demon can pass on those reduced size primaries. But recall that the secondaries have to be delayed until all those other things have taken place, which are required to keep your engine out of detonation.
So here's a situation;
You are bombing down the hiway at 75=2100, and you encounter a slow poke who because of traffic, slows you down to 65 say. So now you are at 1820 still in lock up, and you're looking for a hole to get around him, and when it appears, you floor it.
Ok so, the Vcan drops her load, the timing drops to 32*, and the carb is desperate to open the secondaries. But at 2100 she has to wait, you made it so. Next the loc-up drops out and the Rs climb to 2200, next the trans hunts for second gear, finds it ,downshifts into second and the Rs climb to 4200@65mph, and still at 32* timing. Now yur set for the secondaries to open, and good thing cuz at 4200 your engine, now at maybe 85% VE is asking for 400cfm. And don't shift her until back at 75 mph now at 4900 in second, where she might be calling for 520cfm at say 95% VE.
That's how it has to work, with factory timing controls, when biased for fuel economy.
But recall that I guessed at the 56* of cruise timing. What if your chambers want more? Less will be easy, but more ; not easy at all. Maybe impossible. But be of good cheer, those last 4 degrees hardly amount to spit difference in terms of mpg. They are bragging rights, for when you come on FABO, and present a number so high that everyone will immediately pounce on you, saying it's impossible. When that happens, my response is this;"Just cuz you can't get this number, doesn't automatically make it impossible".

With aluminum heads it's a different story. A better story, way better . But you have to consider the whole combo, and optimize it. You can't just throw it together and hope for the best.
Well,, with a 360, it actually does pretty much fall together, partly because of the 3.58 stroke. It's just a very flexible combination. Not dissing your 383 not by any means, just saying.
Now I know the A500 doesn't bolt onto your BB, but I used the 2.74/1.54/1.00 numbers anyway, cuz the 3.23s really like that trans. The A518 will only slow your take-off a lil bit, on account of the starter gear is 11.8% less effective, so you just press a lil harder on the gas-pedal,lol. I mean after all, it is a 383,lol.

Yeah so, just trying to help;
Happy HotRodding
 
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I ran a 750 composite body Street Demon on what has to be the biggest oven of an engine compartment, an A100 van with the engine under a dog house where heat soak can be intense. I always lifted the cover after shut down to vent, but the heat was still radiating and soaking into everything. Never ever had a problem running, during stop and go traffic, or restarts shortly after shutdown. No fuel percolating from the boosters or accelerator discharge nozzles. Running a 750 DP now for other reasons, but the Street Demon works great. Excellent throttle response and power. Only had a linkage issue (ford kickdown contraption on throttle was causing some binding, I cut it off problem solved) and the choke flap on my sons 625 kept sticking closed in the tower, hyper extending for some reason. Put a small washer under a nut on the carb stud to act as a stop for the flap. Problem solved. Not sure if its a common issue with them. Its affordable. But performs nonetheless

What kind of binding was the phord kickdown causing? Mine has a small issue where it will not idle all the way down without stabbing the gas pedal sometimes. It has the phord kickdown.
 
What kind of binding was the phord kickdown causing? Mine has a small issue where it will not idle all the way down without stabbing the gas pedal sometimes. It has the phord kickdown.
If you grab that little lever, it should move freely, pulling it forward and pushing it back, if you crack/open the throttle normally with one hand, and grab that ford lever with yer other, it should move freely as you open the throttle to wide open. A while back I got on the throttle hard doing some showboating and went down the road. As I let off to come to a stop the thing kept on reving like a stuck throttle. I whacked the throttle and it dropped back down. Looking at it I discovered that lever was tight on its shaft, but the part sticking up was maybe rubbing on something?? (I'll have to look at it again to see which) causing the throttle to hang up. Lube didn't help. It was too tight, so I just hacked it off. Maybe a production flaw who knows but freaked me out at the time it hung up!
 
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With the 2.94 rear gears; 65 mph is about 2400 rpm. with a cam in your range and decent compression, pretty much any carb will do, on account of the venturies will have plenty of airflow, pushing that first-gen Charger thru the air.
I doubt if fancy boosters or small primaries will offer a significant difference. If you already had a carb in the 700 to 850 range, I would just bolt that on and go, cuz you can buy a lotta lotta gas for what a new carb will cost you. And that money would pay for any mileage difference for possibly several years. And in the mean time, you'd have a ripper of a 383.
As for the overdrive, if a GVod; it could be decades before it pays for itself in fuel mileage savings alone. And I wonder if you can run it with 2.94s at 65 mph and a 220* cam. The Rs would be 1850ish, and the typical 220 cam is likely still in reversion down there.
The A500/518 overdrive ratio is even worse bringing your hiway rpm down to; 65=1640, with 2.94s; . And even the typical 210 cam with that short stroke 383, is likely pumping aircharge backwards.

But if you have to buy a carb no matter what;
Then I like your idea of a small triple-booster primary, HUGE rear dump, insulated bowl, and ...... wait;
echos of yesteryear and the 850 ThermoQuad. If you get get your cylinder pressure up closer to the detonation zone, but not into it, then that idea will be dynomite.
It does have that Themoquad moan at wot, couldn't hear it on my van but my sons car with the 625 on it you sure can.
 
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