AVS 2 CFM???

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Bodyperson

Bodyperson

Pedal to the metal
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It seems they jump from 650 to 800 CFM. I am under the impression that a good 340 should have a 750 CFM carb.
I'm thinking of getting the Edelbrock but need a nudge as to which one. The build should go like this so far .
67 Barracuda. Dont really know the weight but yarding the back seat is a lot of weight.
30 over 340 10.5:1 ish.
273 rockers
171 promaxx heads 65 cc.
270 duration 465 lift. Thats whats in it now. Still waiting for the heads.
Dougs headers.
3.91 gears and tall tires... 28 inch??? If I can. Mini tubbed with frame connectors.
Stock converter so far but would like to increase the stall some day.
Dual plane stock 340 intake but the Mopar aluminum version.
Recurved stock electronic distributor.
904 probably but I do have a 727.
Just a street car but I would like to race someday when I can afford it. 1/8 mile track about 3 hours away. Lost Creek race track in Anaconda MT. Probable have to trailer it for that.
Any way... I did one of those CFM calculators but they seem more of a stock configuration.
 
With a 340 with some goodies I would go with the 800.
 
The 650 AVS2 works great on my slightly warmed over 360 in my 69 Dart. From what I read in your post I wouldn’t be scared to go with the 800.
 
I've got the 650 on a 318, but only because I didn't have access to an 800 at the parts store at the time.
 
I have a 650 AVS2 on my current 360, my last one ran a 750 Performer on an air gap intake, warmed over 360, I was very happy with that one, I tried a 670 Holley Street Avenger on it, but it was better with the 750.
 
SGBARRACUDA said:
650 AVS2
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That is a great street carb. For the street use you loose throttle response at low end if you go too big.
I ran a 500 AFB on a 451 stroker and crushed a 427 Chevelle in the 1/8th. Yes he passed me in the 1/4th as I couldn't top end with a small carb.Later I went with a 750 and was running 11.90's in a 65 B body street car.
Right now I run a single 800 AVS on a 472 Hemi on the street.No plans on racing it.
 
With good heads and headers, another vote for the 800. If its too big (and i doubt it) it is essentially a vacuum secondary carb, it wont give more than the motor wants.
(And a two plane intake likes a bigger carb than a single plane. Each half of the intake only "sees" half of the carb, unless you cut down the divider, or run an open spacer.)
 
33IMP said:
With good heads and headers, another vote for the 800. If its too big (and i doubt it) it is essentially a vacuum secondary carb, it wont give more than the motor wants.
(And a two plane intake likes a bigger carb than a single plane. Each half of the intake only "sees" half of the carb, unless you cut down the divider, or run an open spacer.)
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Never heard that. Good to know. I was thinking about cutting the divider.
 
Plastic spacers are cheap (and depending on engine combo, can be the cheapest horsepower there is.... or not) and insulate better than aluminum.
They sometimes aren't available in exactly what you need.
 
33IMP said:
Plastic spacers are cheap (and depending on engine combo, can be the cheapest horsepower there is.... or not) and insulate better than aluminum.
They sometimes aren't available in exactly what you need.
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I think I could fab something from plastic. What are we using? I have a lot of Corian. I plan on taking it to a local tuner guy with a chassis dyno. I would like to be armed with some options.
 
Bodyperson said:
I think I could fab something from plastic. What are we using? I have a lot of Corian. I plan on taking it to a local tuner guy with a chassis dyno. I would like to be armed with some options.
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A lot of the racers make spacers out of wood.
 
I have a couple of aluminum open spacers, both 2", one is a dominator to 4150 adapter.
My small block liked the 2" open, the big block didnt like the dominator, but that was cause the carb was crap.
Im gonna try the dominator adapter on a tm7, with a good carb A to B, with an m1 dominator manifold when i get my stroker together.
(My stuff all has a scoop, or no hood at all.
 
Bodyperson said:
It seems they jump from 650 to 800 CFM. I am under the impression that a good 340 should have a 750 CFM carb.
.
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AFB/ AVS are not double pumpers and are VACUUM CONTROLLED by means of some sort of flapper, same with Quadrajet and Thermoquad and a few others. Therefore a "too big" carb WHEN PROPERLY ADJUSTED, is not "too big." Same holds true of vacuum secondary Holley 4bbl if they are properly set up
 
67Dart273 said:
AFB/ AVS are not double pumpers and are VACUUM CONTROLLED by means of some sort of flapper, same with Quadrajet and Thermoquad and a few others. Therefore a "too big" carb WHEN PROPERLY ADJUSTED, is not "too big." Same holds true of vacuum secondary Holley 4bbl if they are properly set up
Click to expand...
I knew most of that but did not realize all double pumpers are mechanical secondary. Thanks for that. Well google helped. lol
Always thought a big block with a small spreadbore double pumper would be a wicked street combo
 
I had a 650 avs2 on my 360 and it ran good (after spending a lifetime jetting it ) but it was too small at WFO so I installed an 800 version which really helped the top end but lost a little throttle response.

360
9.5:1
Dougs 1 5/8 headers
221/229 @ .050 on a 112 and .511 lift hyd roller.
Ported EQ heads
RPM intake
 
I had a 750 CFM Edelbrock on my 340. It is at about 365 HP with headers, 3.55 gears and 4 spd. It was GREAT when I stomped on the gas pedal, but it ran so rich while cruising in town, my clothes literally had a gassy smell after cruising. I wound up decreasing the primary jets by two sizes. That helped a lot with the gassy smell, and had virtually no affect on performance. After many years, the Eddy carb needed a rebuild. I just got a new carb. This time I got the Eddy 650 Thunder Series carb. I am VERY happy with it. I think drivability in town is much better now. Since I don't race it, the little bit of performance I may have lost is OK with me. It will still melt the tires.
 
Depending on your build and how you use it, you will probably need to jet up a smaller carb and jet down a larger one.
 
The AVS carbs, Carter & Edel are mech sec carbs. All four barrels open when you go to WOT via mechanical linkage. The air valve in the secondaries [ Air Valve Sec, AVS ] controls secondary air flow.

The 800 & 650 have the same size secondaries. The primary bores in the 650 are smaller & that is the difference. It is tempting to go bigger, but your cam is pretty mild & I doubt it would allow the 800 to use all of it's airflow. The smaller primaries of the 650 will also have better throttle response for street driving & for these reasons I would pick the 650.
 
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