Phenolic Spacer introduced acceleration bog

[Spline64]

Hello,

My carb went out last year so I decided to get a slightly larger carb. I went from an Edlebrock 1406 (600 cfm) on my 454 to an Edlebrock 1806 (650 cfm). Seemed to run fine but didn't really see any performance improvements. After doing the CFM calculation for my motor probably should have stuck with the 1406 but hindsight is 20/20.
My issue is I can't run this carb during summer. It will boil the fuel right out of the bowls if you sit at a stop light long enough, so I figured I'd put on a 1" phenolic spacer (square bore). Well that took care of the boiling over issue but now I have a huge bog when I slam the throttle down for about a second before the engine catches up and takes off.
So I'm wondering have I have accented a "too much carb" issue with the spacer? Would a 1/2 inch spacer give less of a bog? My recent internet research has shown that a big block unless highly modified doesn't need a large CFM due to lower rpm's. I only have a mild cam, Edlebrock street performer intake and headers so not very modified.

Any ideas would be appreciated.

thanks,
Spline64

[SkinnyG]

Have you adjusted the idle mixture to see if you can't tune it out first?

[1redbowtie3]

Try swapping vacuum springs, I used a "pink" one that took care of my issue, you may need a richer rod/jet combination on the cruise side also .. you can also richen up the accelerator pump, your bog may be not enough gas.

[Gregski]

I believe they make at least 3 styles of these risers / spacers, and I aint talking about the thickness but the type of hole inside them, there is the one square looking large hole type, there is the four small holes type, and there is one with two oval like holes

my buddy just went through this with his Dodge 318 engine and Demon carb, his motor builder guy said try a different spacer (same thickness) just different design, he did, and it put a smile on his face

so I would like to recommend you try a different design one

[geezer#99]

Crank in some more initial timing first.
That might cure the bog.

[enaberif]

Originally Posted by Gregski

I believe they make at least 3 styles of these risers / spacers, and I aint talking about the thickness but the type of hole inside them, there is the one square looking large hole type, there is the four small holes type, and there is one with two oval like holes

my buddy just went through this with his Dodge 318 engine and Demon carb, his motor builder guy said try a different spacer (same thickness) just different design, he did, and it put a smile on his face

so I would like to recommend you try a different design one

It largely depends on your carb and intake. I have a spacer on my truck and its designed for a quadrajet and I have no bog at all.

Mind you I'm also running close to 18* BTDC for timing.

[RodsGreen10]

The bog on acceleration is a lean spike. The afr is going lean creating the bog. Go up a jet or 2. This should resolve your issue. Also could be you are needing more pump shot. But I am a Holley style carb guy. Also I suggest investing in a AFR gauge so you can actually see what it is doing and tune the carb properly.

[rich weyand]

OK, wait a minute. Before you change the timing or the mixture on an engine that uis otherwise running well, try addressing the actual problem.

When you open the throttle at high vacuum, air rushes in. If not addressed this causes a lean bog. You need extra gas. That is the job of the accelerator pump.

So first thing is to check and adjust the accelerator pump. The Edelbrock has three holes on the accelerator pump arm. Change the actuating rod on the shortest hole -- the one closest to the car -- first, and see if that fixes the problem.

Next after that is to look into what size accelerator pump nozzles are on the 1405.

This pic shows the accelerator pump actuating rod on the lowest setting -- the hole at the end of the arm.

[piecesparts]

Originally Posted by rich weyand

OK, wait a minute. Before you change the timing or the mixture on an engine that uis otherwise running well, try addressing the actual problem.

When you open the throttle at high vacuum, air rushes in. If not addressed this causes a lean bog. You need extra gas. That is the job of the accelerator pump.

So first thing is to check and adjust the accelerator pump. The Edelbrock has three holes on the accelerator pump arm. Change the actuating rod on the shortest hole -- the one closest to the car -- first, and see if that fixes the problem.

Next after that is to look into what size accelerator pump nozzles are on the 1405.

This pic shows the accelerator pump actuating rod on the lowest setting -- the hole at the end of the arm.

Agree with this one. The spacer is NOT too much and the carb is also NOT too much for a 454. THe 650 is a good all around size and works fine on my 383 stroker engine, along with the 1" spacer that is on it. The trick is in the adjustment of the accelrator and/or fuel jets. I have a full set of jets and needles in my kit and I made a chart up with the sizes to match the flows to what each combination would give me. I then started with the factory installed components and worked my way to a point of smooth operation.

[Tom]

Too much carb? Its only a 650cfm on a 454, its nowhere near too much carb. You need to adjust for the spacer is all.

[wilkin250r]

Ditto. The timing might very well be an issue, I'm not completely discounting that, but this same timing DID work properly at one time. Let's focus on fixing the one thing that changed, before changing something else.

You're local to me (G-ville), I have an edelbrock rebuild and tuning manual I would be happy to lend you that has an entire chapter dedicated to accelerator pump tuning.