Edelbrock Cruise WOT Bog Help

[1972BlueC20]

My truck is running almost perfect, but I've recently developed a bog upon WOT only at cruise. It cuts out momentarily then pulls hard.

It doesn't have any hesitation from a dead stop at WOT. Just at cruising.

Any ideas what I can try first to remedy this problem?

Carb is a stock out of the box 1406 with Electric Choke

[67 cst swb]

Here:
http://www.edelbrock.com/automotive/...&submit=search

enter 1406 in part# search box

then, under the additional Technical Resources click on Carb Owners Manual

read from page 3 to page 14

But the WOT info will be on page 12

Without this guide from Edelbrock, calibrating a Edelbrock is next to impossible, but with the guide it is super easy. And its an easy read.

[1972BlueC20]

Originally Posted by 67 cst swb

Here:
http://www.edelbrock.com/automotive/...&submit=search

enter 1406 in part# search box

then, under the additional Technical Resources click on Carb Owners Manual

read from page 3 to page 14

But the WOT info will be on page 12

Without this guide from Edelbrock, calibrating a Edelbrock is next to impossible, but with the guide it is super easy. And its an easy read.

Much appreciated, I will give it a read....

[BruthaMan]

Had this issue, but also from stop, on my 383 stroker in my '78.

Spent a good deal of time reading on it, and came across this recommendation:

http://www.camaros.net/forums/showthread.php?t=137136

Once I upgraded the accelerator plunger, problem solved.

[steelhorse]

Before doing anything to the carb make sure your ignition system is working properly. I have seen a lot of people chasing carb issues that were really ignition system problems. If you have not switched to an electronic ignition system it is money well spent. I have seen cars pick up close to 50 hp by switching.

[1972BlueC20]

I have a brand new crate engine with Chevy HEI system. Most likely it's not the ignition system, but you have a great point. Thx

[1972BlueC20]

Originally Posted by BruthaMan

Had this issue, but also from stop, on my 383 stroker in my '78.

Spent a good deal of time reading on it, and came across this recommendation:

http://www.camaros.net/forums/showthread.php?t=137136

Once I upgraded the accelerator plunger, problem solved.

So did you use that marine grade accelerator pump? If so, did it work?

The 1468 pump says it's not for the 1406 carb. According to info online the pump # 1471 works on the 1406 carb.

[piecesparts]

One thing the Edelbrock and Carter AFB design carbs suffer from (Yes they ARE the same carb design) is the fact that the bowls will have an issue with heat build up and under heavier loads, they may bog. If all else fails look at putting a 1" spacer under your carb to isolate the heat from the carb. I do like the input on the new 1468 accelerator pump.

[1972BlueC20]

So does the 1468 pump work on the 1406 carb??

[BruthaMan]

Yes. I also put it on 1406 on my '72 last year, during a carb rebuild.

[67 cst swb]

Originally Posted by 1972BlueC20

...I will give it a read....

Read pages 3-14 first, before you spend a nickel on parts or lay a finger on a screwdriver.
I know where Houston is, don't make me come down there an read it to ya.

[1972BlueC20]

Originally Posted by 67 cst swb

Read pages 3-14 first, before you spend a nickel on parts or lay a finger on a screwdriver.
I know where Houston is, don't make me come down there an read it to ya.

LOL....yes sir!!

HA

nah but for real....I'll read it today

[SS Tim]

Was this present before or after you installed the leaking regulator?
http://67-72chevytrucks.com/vboard/s...d.php?t=659068

Like 67 cst swb pointed out throwing parts at a problem isn't nearly as effective as understanding the problem and the ramifications of changes made.

[1972BlueC20]

Originally Posted by SS Tim

Was this present before or after you installed the leaking regulator?
http://67-72chevytrucks.com/vboard/s...d.php?t=659068

Like 67 cst swb pointed out throwing parts at a problem isn't nearly as effective as understanding the problem and the ramifications of changes made.

I attempted to install the fuel pressure regulator one weekend and after noticing it was leaking I just removed it and put everything back the way it was because I didn't have any teflon tape at that moment.

The bog actually just started one day.....the only thing that I did just before noticing the bog was put a heavier return spring on the carb and I tried a differnt gas station in my area. I thought the gas might of been the issue, but I already ran it almost dry and refilled with my normal gas....still have the bog and I've driven about 50 miles on the gas that I've always used....all the other gas should be all but gone from the system.

Could the return spring have any effect?

[adricar1]

is not the stock edelbrock accelerator pump adjustable? you can move the circlip in one of three positions?

[67 cst swb]

Be sure you are not pulling the throttle open past full open...
instead of the butterflies open like this |
they are past center like this /
effectively reclosing the butterflies.
I am not sure Edelbrocks are capable of this (don't remember)
Have someone step on throttle (while engine in off, not running) and watch the butterflies open.

[mechanicalman]

Originally Posted by 1972BlueC20

My truck is running almost perfect, but I've recently developed a bog upon WOT only at cruise. It cuts out momentarily then pulls hard.

Did you ever check the accelerator pump linkage like I told you before when you first said you had this problem?

[1972BlueC20]

Originally Posted by mechanicalman

Did you ever check the accelerator pump linkage like I told you before when you first said you had this problem?

I moved the accelerator pump lever to the top hole....didn't make any noticeable improvement....what can I do next?

Change the accelerator pump itself? I have the # 1470 pump on hand.

My next course of action would be experiment with the step up springs and metering rods.

[leftybass209]

Did you read the info posted in the link yet, and have you installed the regulator with teflon tape? Digging into the carb is a last resort, last ditch effort, after you've correctly diagnosed and performed all fixes while the carb is bolted to the manifold. Changing accelerator pumps and metering rods and springs are all for special case circumstances. Swapping those things out WILL cause other issues if the carb could have been fixed with an external remedy. Until you can guarantee 100% without a shadow of a doubt that carb is getting no more than 5.5 psi, nobody can help you and you're chasing your tail.

[mechanicalman]

Originally Posted by 1972BlueC20

I moved the accelerator pump lever to the top hole....didn't make any noticeable improvement....what can I do next?

Change the accelerator pump itself? I have the # 1470 pump on hand.

My next course of action would be experiment with the step up springs and metering rods.

Do the pump, start with the lower hole and go from there. Reason to start with lower hole: The pump you now have may have dried out from sitting so you don't want more enrichment than you need, it's easy to move up.

You could put it in a higher hole to start, but you would never know if you were too rich. If you start in the lower hole, and if it hesitates, and if upon moving up one hole at a time you fix it, you know you have it right. And it's easy to move that linkage.

BTW, you can easily remove the upper cover of the carb on the car, just hide the car keys while you do it and remove the positive battery cable first for safety.

[1972BlueC20]

It's showing right at 5.5 PSI on the gauge at idle....I haven't installed the regulator yet....going to do that this weekend. The pressure appears to drop a little when I rev the throttle with my hand.

Yes I read through the manual. Seems that according to the manual bogs are caused by either air leaks or too rich or lean conditions.

I will spray some carb cleaner around the base plate while running tonight and see if the idle increases.

[mechanicalman]

Originally Posted by 1972BlueC20

It's showing right at 5.5 PSI on the gauge at idle....I haven't installed the regulator yet....going to do that this weekend. The pressure appears to drop a little when I rev the throttle with my hand.

Yes I read through the manual. Seems that according to the manual bogs are caused by either air leaks or too rich or lean conditions.

I will spray some carb cleaner around the base plate while running tonight and see if the idle increases.

You may also have an issue with the secondary air valve. If the fuel pump regulator or accel pump do not fix it go after that next.
Here is an excerpt from the link and the link itself.

http://www.thecarburetorshop.com/AFBtuningtips.htm

The auxiliary airvalve

One of the least understood issues of tuning the Carter AFB is the importance of the auxiliary airvalve.

Carter supplied many different airvalves in their various AFB carburetors. Since most do not have a ready supply of airvalves, and they are not readily available, the easiest way to tune this variable is START WITH THE PROPER CARBURETOR FOR THE APPLICATION!

The auxiliary airvalve controls the timing of when the air starts to flow in the secondary circuit. The fuel will have already begun to flow through the secondary starter circuit. The airvalve consists of a shaft with two valves, and two offset weights. Since Carter used a variety of weights, most enthusiasts think that the weight is the tunable variable AND NEGLECT TO LOOK AT THE ATTACK ANGLE OF THE VALVES.

Yes, the weights ARE important, but the attack angle is easily as important, if not more so. We have had many carburetors come to us with weights ground almost to nothing, or chunks of lead screwed onto the weights when the angle of the valves was incorrect for the application.
For STREET vehicles (you know, no 9000 RPM start from a stop sign, just spirited driving) GENERALLY, "torquer" engines like a small attack angle; and "screamer" engines like a large attack angle.

Sometime take a look at the angle on an original AFB for a Pontiac, Buick, Chrysler, etc., and then compare it with the angle on the aftermarket AFB's.

Using the large angle as found on the aftermarket (SBC) carburetors on the torquer type engine causes the airvalve to whip open too soon, which may cause a hesitation or bog when the secondary begins to open.

Conversely, trying to use one of the Pontiac valves on a SBC will cause the engine to starve for air, and lose power as the secondary begins to open.

Again, since few enthusiasts have a large selection of the various airvalves, the easiest method of tuning is to start with the correct carburetor. Carter did not build 505 different AFB's just to remove the R & D money from the profits of the shareholders. One size or type does NOT work for all applications.

[1972BlueC20]

Originally Posted by mechanicalman

You may also have an issue with the secondary air valve. If the fuel pump regulator or accel pump do not fix it go after that next.
Here is an excerpt from the link and the link itself.

http://www.thecarburetorshop.com/AFBtuningtips.htm

The auxiliary airvalve

One of the least understood issues of tuning the Carter AFB is the importance of the auxiliary airvalve.

Carter supplied many different airvalves in their various AFB carburetors. Since most do not have a ready supply of airvalves, and they are not readily available, the easiest way to tune this variable is START WITH THE PROPER CARBURETOR FOR THE APPLICATION!

The auxiliary airvalve controls the timing of when the air starts to flow in the secondary circuit. The fuel will have already begun to flow through the secondary starter circuit. The airvalve consists of a shaft with two valves, and two offset weights. Since Carter used a variety of weights, most enthusiasts think that the weight is the tunable variable AND NEGLECT TO LOOK AT THE ATTACK ANGLE OF THE VALVES.

Yes, the weights ARE important, but the attack angle is easily as important, if not more so. We have had many carburetors come to us with weights ground almost to nothing, or chunks of lead screwed onto the weights when the angle of the valves was incorrect for the application.
For STREET vehicles (you know, no 9000 RPM start from a stop sign, just spirited driving) GENERALLY, "torquer" engines like a small attack angle; and "screamer" engines like a large attack angle.

Sometime take a look at the angle on an original AFB for a Pontiac, Buick, Chrysler, etc., and then compare it with the angle on the aftermarket AFB's.

Using the large angle as found on the aftermarket (SBC) carburetors on the torquer type engine causes the airvalve to whip open too soon, which may cause a hesitation or bog when the secondary begins to open.

Conversely, trying to use one of the Pontiac valves on a SBC will cause the engine to starve for air, and lose power as the secondary begins to open.

Again, since few enthusiasts have a large selection of the various airvalves, the easiest method of tuning is to start with the correct carburetor. Carter did not build 505 different AFB's just to remove the R & D money from the profits of the shareholders. One size or type does NOT work for all applications.

Thanks a lot man, once again your are a great help!

[SS Tim]

Originally Posted by 1972BlueC20

...The bog actually just started one day.....the only thing that I did just before noticing the bog was put a heavier return spring on the carb and I tried a differnt gas station in my area. I thought the gas might of been the issue, but I already ran it almost dry and refilled with my normal gas....still have the bog and I've driven about 50 miles on the gas that I've always used....all the other gas should be all but gone from the system.

Could the return spring have any effect?

Going back to the root of the problem. It worked fine and then developed a problem. That isn't an adjustment issue. Look over all your basics hard before doing more "what if I do this..." tinkering.

Is your return spring part of the problem and is the linkage/cable binding somehow?

Checking for vaccum leaks is also a good idea as you are planning to do.

Sometimes its the simple stuff that causes an issue. I've seen probably 10 or 12 new car warranty performance issues as a result of aftermarket floor mats binding the accelerator pedal. Most of the time its a second set over the factory mats "to keep them clean".