AVS2 Edelbrock 1906 Infamous BOG Updates!

Showing my findings about the infamous Edelbrock AVS2 BOG upon immediate throttle and another step closer towards making this carburetor scream some more on my 5.9L Magnum in the '73 Scamp.

Note: Later in this vid I talk about some back fires I've had with my configuration in the Scamp. My backfires sometimes happen because I am using an HEI Ignition module that's tied into the ballast resistor wire harness as an ignition source. There's a slight voltage loss there that's enough to make it so where it will never fire up normally until I let off the key, sometimes because of this it'll gently backfire, or fire right on up, attempted to fix this with a 12v relay with no luck, but it will fire up normally if the module is directly hot wired to the battery, so timing is all set right where it needs to be. Running 36° Total advance. I've ran a couple different used Holley carbs shortly that had drivability issues on this drivetrain configuration, but they both worked fine upon flooring it with 0 bog issues, the current AVS2 carbs I own now are on this Scamp and my '81 Z28 Camaro with a vortec headed 350, the bog is much worse on the 350, so it's been a challenge smoothing it out but never fully finding the cure.. The blast plate didn't make much of a difference if at all to be honest, but it was worth a shot!

[gergatron]

I wrestled with a Street Demon for quite a while (the modern version of the ThermoQuad) and the biggest issue, apart from the lack of ideal jets and rods, was the accelerator pump. It was very much hit-and miss, where you'd get it working ok in the driveway, take it out and the bog often came back. Pulled over, and could see that there was no fuel coming out of the squirters. I put that down to a weak pump cup seal, so i wedged an o-ring inside it to try and help it seal in the bore. That plus a stronger spring on the back of the piston helped to fix it.... mostly but never completely. I went with a spreadbore 650 Holley pumper and have never looked back.

[gansh]

At 17:10 in the video you mention moving the pump location to the lowest hole to "slow down the pump shot" and yet you have an "Edelbog" issue due to a lean spike at WOT. I don't think you want slower, so have you considered instead moving the AC pump location to the middle or top location (to speed up the shot) and possibly going back to a smaller nozzle orifice size if this results in a bog (too rich?)? Also it is good to make sure your step up spring is correct to transition to Accel from Cruise immediately to ensure that the primary needle is helping as soon as possible in WOT. This is the direction I went after testing all possible pump locations with all possible nozzles sizes while watching the O2 AFR graph. I have a different setup, but what I saw on the graph was a lean spike in the first 1/2 second of WOT after a throttle stomp, so I wanted more fuel faster, not slower. I went with the stock pump nozzle (28) on the top hole with the silver step up spring (the correct spring depends on your specific engine vacuum). Also like you I have the Thompson PowerBlast Plate installed with secondary clusters with the smaller emulsion tube removed.

[deerslayer]

On the nozzles larger ones dont give you more fuel it just delivers it faster

[gwmax]

Sorry all who's watching this, this isn't the most best production made video I've made in a while, threw it all together on my phone at 3am and on the verge of falling asleep.. The CC-close captions do a pretty good job if you can't hear what I'm saying at points where I accidentally had my hand covering the mic on the phone, plan on making better future videos soon and maybe finally making something out of this channel, not too crazy. Keynotes I will say for playing around with these AVS2 carbs, right out of the box your float levels will be set wrong, and they have to be corrected. There's plenty of vids on the tube where you can figure out how to set them properly, and it's a key factor in performance and drivability in these carbs, as well as having the correct fuel pressure setup, which is around 4.5 to 5 max from what I've been experiencing. Plus, having correct ignition timing is very important. Get yourself a low psi turn dial that comes with 3/8 fittings, use liquid teflon tape on the threads to seal n' setup completely after 24 hrs, also have a fuel pressure gauge after that so you can see where your pressures are at. Most of those low psi electric fuel pumps out there have built in internal regulators, which can be super convenient, but also sometimes work against ya when it comes to setting fuel pressures. Take your time, take pictures of your configurations, take detailed notes on what you do each time you make an adjustment, over time you can get these carbs to work much, much better vs out of the box. Every application is different, gear ratios, engine displacements, flow rates, vehicle weights, etc, nothing is the same car to car so you have to tune to what you have. Some people eat more than others, and some people don't. Some people spend more time on the toilet after eating betos every day, and others may tailor towards swapping a holley on, everything's different.

[rogeroaks]

Ignition timing/curve can contribute to a hesitation. Try a little more initial timing and see if it helps.