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4 Posts
Discussion Starter · #1 ·
Long time lurker, first time poster. Im sorry that this is a repost in a different category, im still figuring things out.

I got to know my Edelbrock 1806 650 AVS carb recently, and found a lot of useful, but scattered, information on this site to help me tune the carb.
I would like to start a tech/setting list for edelbrock carbs. If there already is one, my apologies...
Please list motor,carb,intake,climate with changes you made to carb and results. Maybe a little story too.
I'll start.

Motor - 350ho. (vortec heads)
Intake- Rpm Air Gap
Carb- Edelbrock 650 1806 thunder avs
Climate- Sea level, winter, dry and cold 25-35d. January western wa state.

Ran okay with performer intake 1806 650 edelbrock carb, but I expected more from a "HO" motor. Switched to RPM Air Gap intake and there was a noticeable power increase, but the engine would bog so bad that it would pretty much die when it was floored. I was also having some pinging with heavier accel. Suspected lean condition due to better flowing intake or fuel pump not up to the task. It also had extended cranking time when the motor was hot (20 min or so after shut down). I know, I know, buy a 750 Holley. I wanted to give the new Edelbrock that came with the car a try before losing $500. Cruise and light-mid throttle excellent. Idles smooth, 16" vacuum.

Step 1- Adjust floats (way off). Build fuel system with high flow pump and pressure regulator (set to 5.5psi). Check base timing, back way off timing advance until pinging stops. Severe WOT bog unchanged

Step 2- Tried several combinations of rods/jets/step up springs. AVS settings.

Best results
#2 on tuning chart (1 1/2 richer power mode only)
Silver 8" step up spring (strongest)
Top accel pump hole, rod straightened/lengthened slightly
3 stages rich secondary jets (tried stage 2 first and bog was much improved but still there).
2 1/2 turns on AVS Valve. (AVS also helped to tame the bog)
.30" Edelbrock insulator spacer/gasket (helped with hot extended cranking time)

The step up springs were the only thing I ultimately used from the "tuning kit" wasted $50. It did however show what didnt work.

The bog is still there slightly, for a second, if I stab wot. Non existent when I roll the throttle to WOT and I was able to add the timing back in without pinging. Runs like a raped ape. Feels like an honest 375hp. The larger secondary jets and avs adjustment had the biggest effect. I suspect there will not be any bog when the weather warms up, and it will lose some power as well. These cold and dry days seem almost optimum for performance.
Still wonder if I am leaving anything on the table not buying a double pumper...It would have been helpful if the hotrod magazine that published the significant power gains with the rpm/holley swap showed the gains separately.

1,218 Posts
Sounds like a similar issue I had with my Holly 650 DP. After I played with the floats, and got my dizzy timing right. It worked out pretty well with minimal bogging. I'm not an expert in this area. I tend to adjust things according to videos I find on YouTube.

5,422 Posts
Before these aftermarket AFB/ AVS carbs got popular I was running the old AFB's and people told me in the 1980's to get a Holley.
Too bad for them as I learned what the AFB really liked.

In fact in my teens I learned what just about all carbs liked by spending many days tinkering with them.
I learned what some do not like also and I made junk from a couple carbs.

Try this to eliminate your bog. while engine is off

Loosen the screws that hold the covers over the primary metering rods and power piston.
Clock the small flat cover so that 1/2 of the hole is exposed , snug the screws.

You should be able to see the power piston top.

Start the vehicle.
That piston should be down in the hole at idle. Now blip the throttle just slightly.. the pistons should jump up quickly and hit the cover plate.

Raise the R's slowly to say 2000 or so hold it for a second there , Then give the throttle a quick little blip.

Power piston should jump up.
If it does not you need more spring under it.
CRAP! you say you have the heaviest spring in there now.

Yep that is usually the case. Back in the 1980's I would add ink pen springs inside the factory springs to make more spring tension.

You want the stiffest you can get by with and still have the pistons stay down while at idle in gear.

If the power piston jumps up and down at Idle you need a lighter spring.

I run 7.5 psi on mine Never any issues. But 4 psi will also work.

I have posted the ink pen spring thing before and it works well if that is the issue.
Sometimes it is a right foot moving way too quick, It is a carb and you can bog even the Holley with Superman speed foot stomp.

I had a buddy that would just go way too fast and hard ,I thought he was going to bust a hole in the floor.

1,865 Posts
To fix a Holley, you buy a AFB/AVS. Not the other way round....

The factory float level is 7/16". I would try 5/16", which will raise the fuel level 1/8" & start the secondary system with less airspeed. May completely cure any flat spot. Simple test, easy to try.

You say you are using the stiffest piston springs; if the engine has a cam larger than stock, then I would think you will need softer springs. Jeff's test above is a good test, pistons should be down, idling, in gear if auto. Any piston movement at idle means the springs are too stiff.

Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
29,330 Posts
LOL, Geoff, "To fix a Holley, you buy a AFB/AVS"

to fix and AFB/AVS I install a Holley, but not a dbl pmpr on a small block in a heavy car. 600 vac sec would be the cure there.

Why would it make any difference what the PVs are doing at idle? They add fuel to the main circuits which are not feeding anything into the engine at idle. The idle wells are already full, and can pass something like 50x more fuel than the idle circuit can use.

A little birdie tells me we are never going to agree on this, so WTF, over? ;)

1,865 Posts
Not sure if the latter part of your post was aimed at me or Jeff. But I never claim, & have claimed, that a piston failing to stay down on a Carter/Edel/QJ carb, or an open PV on brand H & clones, will cure a bog.

However, it is probably possible that if the PV was open during cruise conditions AND the the engine had a weak ign system, the sooted up plugs may not fire when switching to WOT & could create a stumble.
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