AVS2 800 carbs

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midnight340

midnight340

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If this hasn’t been posted, and for anyone who is interested:

I called Edelbrock yesterday and was informed that, yes indeed, there is an 800 version of the newer AVS2 carbs on the way. Annular booster AVS, and they are taking pre-orders now. Shipping soon I’m told. :thumbsup:

( public announcement, not meant as invite for bashing of Eddy carbs by diehard fans of those great Holley carbs!!!)
:rofl:
 
For Edelbrock 750 owners, I'll add this information for anyone that it might help:

When I first came to this site with some problems a couple of years ago (?) I didn't know much about tuning. Well, it's been an education!! But a lot of fun to figure some things out. Here goes:

Don't let anyone tell you that you can't tune the 750. Yes, they do in fact have some limitation in the amount of fuel that they will ultimately supply in the secondaries, but for most people I think frustrations lie elsewhere. (This is my experience, my findings, so things might be different for others!)

I have a 9:1 340 with ported X heads, mild 284 Lunati cam, that likes a lot of fuel with the throttle down, but doesn't need so much at part throttle. Other motors will vary in needs, but here are a few things that might help if you are having problems with:
Rich idle and smelly exhaust
Throttle response
Flat spots, etc.

Throw away the book!!! Watch the plugs or get an A/F meter and vacuum gauge.
Biggest help for me was doing these things:

--Use an accelerator pump from the 800 (#1468)
--Install .043 accel. pump nozzles/"squirters" (#1475 for kit)
--Don't be afraid to use bigger jets in secondaries than you use in primaries.

MY OWN EXPERIENCE!!!
I run .104's in front (68x42 rods right now) and have .119's in back*
(*I find that .110/.113/.116/.119 all give me the same A/F readings, so there's the limitation in back that the 800's don't have.)

My A/F readings:
Idle 13.5 at 800rpm (max. vacuum) screws 3/4 out
Light throttle 12.5-13
Steady cruise at 2200 in town, or highway in O.D. 13.5-14 (4.10's with 518 trans)
WOT 12-12.5

(Vacuum reading at WOT is 1-1.5" so carb is sized right)
Timing 22*/34* total.
Throttle response is crisp off-idle or from low rpm. Engine pulls good.
Plugs have a nice tan ring at base of porcelain and light black all around the base, timing mark right at bend of strap.

I have an A/F meter and vacuum gauge plus a lot of testing, so am fairly sure of my #'s, and am fairly happy with the manual choke 750 right now, but it's faster at the strip if I jet too rich in front to make up for the limitations in back. For this reason I'm going to the new AVS2 800.
 
midnight340 said:
If this hasn’t been posted, and for anyone who is interested:

I called Edelbrock yesterday and was informed that, yes indeed, there is an 800 version of the newer AVS2 carbs on the way. Annular booster AVS, and they are taking pre-orders now. Shipping soon I’m told. :thumbsup:

( public announcement, not meant as invite for bashing of Eddy carbs by diehard fans of those great Holley carbs!!!)
:rofl:
Click to expand...
I got the AVS2 650 on my 340. Best carb I've ever bought. Runs better and starts way easier.
 
Go Mango said:
I got the AVS2 650 on my 340. Best carb I've ever bought. Runs better and starts way easier.
Click to expand...

Good to hear, I've read that the low end response is really good with the AVS2 boosters too. I went back and forth as to getting the 650 or 800, then read in a tuning book I have that if WOT vacuum is under 1" the carb is too big, and if it's over 1.5-2" then the carb is too small. My 750 hovered right between so think I'll try the 800. I'm often told the 650 would be better around town and for general driving. (I think that's true, I used to have a Performer 650, plus I got a bit better mileage with it.) ....But I have this brother I run against at the strip every year and he thinks he's faster (sometimes) so WOT is important. :D

I'll report back if the 800 seems too big.
 
It's about time! I have an 800cfm Thunder that is pretty good and easy to tune. I would love to try the AVS2.
 
I just watched the excellent video in the tech section on how to pick the right size carb.
Since I consider myself to be in the state of always learning, I'm now wondering if there is any downside to going with the AVS2 650 vs. the new AVS2 800.

I do have the 4.10 gears, about 2800 stall, Cope built 518, LD340 intake, the nice flowing heads, cam is the old Lunati 284 Bracket Master cam, 1-5/8 headers with 2-1/2" exhaust with Magnaflows. Weight is about 3300 lbs. Current 750 carb has crisp response.

That video would suggest I stay with the 650 to keep more velocity through the boosters. Do the annular boosters and AVS secondary change this advice any?
(I know 340's always seemed to do well with larger carbs...)

Just opening up the issue to see what other's experience is with 340 carb size.
 
midnight340 said:
Good to hear, I've read that the low end response is really good with the AVS2 boosters too. I went back and forth as to getting the 650 or 800, then read in a tuning book I have that if WOT vacuum is under 1" the carb is too big, and if it's over 1.5-2" then the carb is too small. My 750 hovered right between so think I'll try the 800. I'm often told the 650 would be better around town and for general driving. (I think that's true, I used to have a Performer 650, plus I got a bit better mileage with it.) ....But I have this brother I run against at the strip every year and he thinks he's faster (sometimes) so WOT is important. :D

I'll report back if the 800 seems too big.
Click to expand...
I'd like to know, because I probably would have bought the 800 if it had been available.
 
midnight340 said:
I just watched the excellent video in the tech section on how to pick the right size carb.
Since I consider myself to be in the state of always learning, I'm now wondering if there is any downside to going with the AVS2 650 vs. the new AVS2 800.

I do have the 4.10 gears, about 2800 stall, Cope built 518, LD340 intake, the nice flowing heads, cam is the old Lunati 284 Bracket Master cam, 1-5/8 headers with 2-1/2" exhaust with Magnaflows. Weight is about 3300 lbs. Current 750 carb has crisp response.

That video would suggest I stay with the 650 to keep more velocity through the boosters. Do the annular boosters and AVS secondary change this advice any?
(I know 340's always seemed to do well with larger carbs...)

Just opening up the issue to see what other's experience is with 340 carb size.
Click to expand...
With a non factory cam(unknown specs) my 340, 4 speed, 3.91 geared dart seems like it might like a little more fuel at high rpm with the 650. The damn thing overwhelms 245/60-14 tires. Low end throttle response is incredible with the AVS2.
 
I have tried the Ede 600,650,750 performers on my car.
Out of the 3, the 750 I liked the least. Never could get it to run the way I wanted. Maybe your write up would help.The 600 comes in 2nd. Great signal, great throttle response. I would imagine the only thing you lose is at the very top end, which I won't do on the street. This leaves me with the Thunder 650. Seems to be the best of both worlds, adjustability, performance. Haven't had the chance to play with the AVS2 yet, like the theory behind it. If I did, it would be the 650 for a SB.

This is on my 360, fairly mild combo, Comp XE268.
 
Looking at the specs the AVS2 650 is more of a spread bore design, even if Edelbrock doesn’t call it that.

The 650 has primaries from the 600 (1-7/16”) and secondaries From the 800 (1-3/4”).
 
Carter-Clusters-Hysteric-label.jpg
Johnny Dart said:
Out of the 3, the 750 I liked the least. Never could get it to run the way I wanted.
Click to expand...
Seems like its the parts Edelbrock usually puts in them.
From Edelbrock 1407 - Speed Talk
Tuner posted "The 1407 750 CFM uses the same casting for the primary cluster as the 625 CFM carbs in spite of the fact the venturi minor diameter is 5/16” or so lower in the 750 body. This places the exit of the booster venturi that much above the “vena contracta” in the air flow, the result is the “booster signal” is not obtained in the correct location and the metering is erratic, the A/F wanders rich and lean as load and RPM vary as the throttle position is changed."
In a post on RFS he mentions a fix: "I made some sleeves out of thin-wall brass tubing that fit over the booster and extended the length down to the vena contracta and with that it worked like a normal carb by inserting a tube sleeve to extend the booster to the proper depth."

There are also variations in the cluster pickup tubes. @Hysteric posted this image on page 3 of the speedtalk thread.
Reposting the photo here because I'm not sure you can sign up for speedtalk at this time.
1. Eddie 750 (1407) 2. Carter 625 3. Eddie 800AVS
file.php


Brief history of the long boosters and their disapperance:
After the company was flipped through a few corporate configurations and Sealed Power - Federal Mogul took over the production, and subsequently the carbs morphed in to the “Weber” Edelbrock versions we see for the last 20 years, the longer booster production stopped and the large venturi ‘750 castings had to use the same high short booster as the smaller ‘625’ carbs.

Needless to say, the 750s with short boosters that don’t reach the vena contracta haven’t been a good carb in all throttle positions and RPM ranges.
 
Last edited by a moderator:
midnight340 said:
Looking at the specs the AVS2 650 is more of a spread bore design, even if Edelbrock doesn’t call it that.

The 650 has primaries from the 600 (1-7/16”) and secondaries From the 800 (1-3/4”).
Click to expand...
Carter avs carbs are that way. The throttle plates are larger on the secondaries than the primaries.
 
Thanks for that info! In spite of all my trying to figure out the 750 carb I hadn’t come across that.

I got mine working fairly well, but am definitely going to the 650 or 800 as soon as I pick a new cam with more lift.
 
midnight340 said:
Thanks for that info! In spite of all my trying to figure out the 750 carb I hadn’t come across that.

I got mine working fairly well, but am definitely going to the 650 or 800 as soon as I pick a new cam with more lift.
Click to expand...
As I stated earlier in this thread, the 650 AVS2 was a game changer, at least for me. I highly recommend it!
 
I’m not sure going to the larger carb is the right move.
 
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