Edelbrock AVS2 650. Tuning tips - Installed on a 400 SBC.

ONE NOTE, I have the accelerator pump linkage installed on the hole closest to the body of the carb ( most aggressive position.) This, along with the strongest springs in the kit do a great job of greatly reducing the lean bog on fast throttle transitions to WOT. Not completely cured, but nearly. Some folks like the "Woomp WAAAA" though... so... This one doesn't do it nearly as bad as some of the cars/ trucks I have driven. This carb is best for a cruiser, occasional tire incineration...general driver type of car. Although not the highest in terms of power output, (usually off by 5-10 hp) , it offers VERY GOOD throttle response and torque under the curve.

[FreeRiderNeal]

Good stuff. A lot of people these days take for granted our efi and how much work the ECU actually has to do. It's good to see not all is lost as is the fundamental knowledge of different ways fuel can be controlled. We've gone from fuel air charge in the plenum, then to fuel air charge in the runners, and then to direct injection.(and now a combo of port and direct injection). It's crazy how far we've come with tech in 30 years. Messing with carbs is almost all but forgotten which is a shame. And to think small children and infants get handed tablets and phones to keep them quiet smh... I'm thankful I grew up with a father that taught me how carbs worked. Understanding the fundamentals is definitely important. Now that I'm 28 and having been working on these new vehicles I get to teach him the tech I'm working with on 2022 vehicles. It's astonishing that automakers are now considered tech companies. 90% of my work is done through a computer screen with multiple programs for programming, looking at complete vehicle data and codes, calling engineering to get special programs for vehicles, and a communications interface that allows me to monitor all modules for connection issues so intermittent if you blink, the network goes down and comes back on causing multi-system failure. It took me 6 months once to diag a intermittent TCM loss of comm due to high trans temp. I drove that car almost 1000 miles to compile data in order to pinpoint the exact cause of failure. Turns out the customer drives the car in an abusive manner which is why it took me so long to figure out the problem. The trans temp had to get to 290°F before the TCM/valve body would break comms on the highspeed buss which is 15°F under the threshold to turn on an MIL for high trans temp. I finally got to drive with the customer and he treated the gas pedal like a light switch (was a 1.8L N/A Chevy Sonic) during that 1000 miles, it only acted up 3 times. Complaint was no power steering, CEL for loss of communication with every module, and reduced engine power.(Basically limp mode). Most people think we can just "plug in the scanner" and automatically know what's wrong. While that may be the case for repeat failures, but when it's something that even Technical assistance and a field engineer couldn't figure out, I was forced to take a different approach to diag because no one, and I mean NO ONE drives like he does. And of course he denied that was the cause. But at the end of the day his extended warranty bought a new transmission and TCM since he cooked both. If it was GM warranty, he'd be up shit Creek. I appreciate all of the info you give on your channel because I know right where it's coming from. Trial and error are the best teachers next to you!

[SpeakerKevin]

Finally, someone who understands how to set up the step-up springs! Thanks.

[novaguy]

I’ve run Edelbrock carbs for years. Not the best choice for top performance, but they’re excellent carbs for street use and still work well at the track.

I always start by setting float height to 3/8” and float drop to 1”. Swap out the stock step up springs for the silver 8” springs. Move accelerator arm to bottom hole for biggest shot. Set idle mixture using a vacuum gauge set to highest vacuum reading, usually 1-1.5 turns out.

Before doing that it’s best to run as much initial timing as you can. I like running 18 degrees initial minimum for aggressive cams with 32-36 total all in around 2500-3000rpm. Stock cam will run less like 10-12 initial.

Carbs are primitive compared to efi but they’re easy to work on and adjust once you understand how they work.

[Eleannos]

Thanks, I just picked this up for my 68 Pontiac firebird 400. Gonna go ahead and change the step up spring before I install it.

[tonycolca]

It comes with the orange spring 5hg that means at approximately that amount of vacuum the metering rod will lift and go rich. General rule is use spring that is rated half of idle vacuum. Most edelbrocks come with orange spring. One of their 600 cfm carbs come with yellow spring.

[tonycolca]

The stock spring is the orange spring 5Hg.

[frankmiller]

Don't know what AVS2 you got, but it sounds like you got one too small for your truck. The AVS2 is definitely a performance carburetor. The "flapper" you refer to is called the secondary air baffle, which makes up the Adjustable Vacuum Secondary (hence AVS). Also, so people don't get confused, the "needle" you're referring to is called a metering rod and it sits in the jet not a seat. Under normal circumstances, is sucked down by the engine's vacuum, which decreases once the throttle is opened, thereby allowing the spring to push the rod up and out of the jet. So, in your case, the engine was producing too much vacuum to allow the metering rod to do its job, which is why you had to upgrade the spring. Having to use the strongest spring in the set is very unusual for a mild stock engine. Hopefully you used the tuning chart and also selected the correct metering rod when changing the spring.

[harveynewman]

i have the avs2, 650 on my 1998, gmc, savana van, 5.7. works great but i have heat soak issues. gonna try installing the insulator, sold by edelbrock. dont know if there will be enough space for it. had to make room on top of engine opening, inside the cab for clearence. its on a EPS, intake, with HEI, DIST. getting about the same fuel mileage .

[shootermcgavin]

The 400 pulls lots of vacuum. That's why you needed a heavy spring

[shortattentionspangarage]

Good on you for using a Wideband to tune. Youtube is full of "tuners" who have no idea what their AFR is yet they still toss out suggestions. I've been using a wideband since 2011 to tune everything. AEM makes the best and it's cheap.

[rongray]

Im having run on (dieseling) with my 440. Doesnt do it with the old style edelbrock.. cant figure it out. Timing is set correct, fule pump set at 5.5lbs. Runs beautifully, just will not shut off unless i dump the clutch

[KurtTank]

B Mason, because of the year, your C10 most likely didn't come with a Oxygen sensor, where did you install it and why, how about using a vacuum gauge or going by sound of engine. An owner of a 68 ford f100 with 390 fe 2bbl engine with hedman headers. I stopped watching the All Star game to view your video. Now that's dedication

[coryharley]

Thanks for the info. What is the spacer under the carb? Have a c20 also and a ton of room. Going to be putting a new carb on soon and not sure the best way to aviod heat soak. Tanks again.

[bikepackHotrod]

SO if it's too small you can re-Jet this like a holley and also change the spring?

[anthonyvene]

I couldn't believe how exact your experience was with my almost identical setup and timing results, RV style cam motor that has huge vacuum of 22 requirs the strongest springs, also went to the longest throw on accelerator pump position. What I'm experiencing now is at about a quarter mile of driving at half throttle and when you floor it there's no more gas left in the bowl to burn, engine feels off lol, so I know I need bigger mains. Is that primaries or secondaries? Plugs were on the extreme lighter side after some WOT runs. Tire roaster off the line right now, didn't do that with the stock 5". Thanks! Probably should have a 700cfm on her but too much money right now

[c]

Adjusting the air valve baffle on the secondary will also help eith thst flat spot

[lordsauto]

I also use the plain works great stock 350 chevy

[armygreenfj]

I got a rebuilt chevy with a mild 350 edelbrock top end kit.. i havent adjusted the springs yet on my AVS2 650..im curious to see how much better it’ll run..

[optimusprimer]

Mine Idols once it's warmed up with a 10.1 air fuel ratio sometimes 9 and I cannot get it to lean out it is a stock 400 fresh rebuild same old bolt-ons

[yusefkabib]

So what’s a performance carb in your opinion? Hot dog ! The avs2 was made for performance the way it was designed and a bit upgrade from the 600cfm edelbrock. Wow man! If a 650cfm 4 barrel carb with annular boosters is just a “cruising” carb... you got me! 🤷🏾‍♂️