Need help with carb adj on Edelbrock-350

[sixdogs]

I know this is a tractor site but all I know are tractor guys and I want an answer from a tractor person. I don't know where else to turn.

I have a small homebuilt vehicle with a new, stock 350 GM engine that I put an Edelbrock manifold and 600 cfm carburetor on. I heve the timing correct and all parts are new but the vehicle "stumbles" or bogs down on acceleration. Not real bad but it bothers me.
I have no vacuum leaks and think it is the air-fuel mixture but don't know what I am doing. All I know is diesel farm equipment.
The guys here are pretty creative and I am sure solved this problem before. I have been trying to fix this for two years and would appreciate any advice offered. Thanks.

 

[skargo]

I have a e carb on a 67 Pontiac of mine. I replaced the accelerator pump with Edelbrock part #1468 accelerator pump. The stock accel pump has a weak spring and this one helped my "bog".

they also have a tuning guide on their website, and a tuning kit with different metering rods, etc for I thin $50.

Is your carb a 1406 or ???

 

[RobJ]

On the flip side if the carb is new the accelerator pump could be putting out to much fuel, there should be an adjustment for that to.

I ran Q-jets on my street cars in the 70's. We use to love that little 1-2 second bog because after that it was hang on. Might even get a wheel chirp. I put a Holley on my Formula once and it didn't bog, car was just as fast but not as much fun.

 

[skargo]

Most with q-jets learned to "foot it" back in the day.

 

[Tig]

When you say stumble or bog do you mean as soon as yet step on it. Or does it bog at a certain RPM?
If it's immediate then the tuning guide advice is a good place to start. Look here.
What vintage is the engine? What sort of ignition does it have? I'm wondering if it has a distributor with vacuum and mechanical advance.
For those who have been out of the carb scene for a while I believe the carb he is asking about is an updated version of the Carter AFB in the pic below.

 

[sixdogs]

You guys are great! I think I have a 1406. The engine is maybe five years old and is a factory stock long block. The bog happens when I step on it regardless of RPM. If the engine is running hotter such as at long idle (200 as opposed to 170 degrees) it has less bogging.
Keep the advice coming, this is the best info I have gotten so far.

 

[dbdartman]

You can try moving the rod to the hole closest to the pivot on the accelerator pump arm. This will give more shot. Try this first. If it clears it up, fine. If it helps but doesn't completely clear it up, the stiffer pump spring sounds like a good idea. You can try by removing your spring & stretching it. Last resort; larger squirter.

 

[Eagleview]

With the engine OFF , look down the throat while giving it full throttle with your hand . It should have a strong steady stream of fuel out of both jets which will continue to spray for a second or two after you hit the throttle stop . If you are only getting a dribble , the diaphram , check ball or spring is faulty . Is the carb a vacuum secondary type ? If it's a double pumper then it's really to big for a 350 . What size cam has it got ? Big cams cause low manifold vacuum , when you stomp on the loud pedal manifold vacuum drops to zero , air speed slows and the engine takes a crap . Is the manifold dual plane or single plane (single plane should not be used on the street just like big cams) A 350 running at 5000 rpm's (being honest) with a volumetric efficiency of 80% needs a carb of 405 cfm . So the formula is :-350cubes X 5000rpm = 1750000 divided by the constant 3456 = 506.36 - 20% lost eficiency = 405cfm .

 

[sixdogs]

I'm going to check some of these things out tonight. I hae a stock basic GM 350 making 260 HP. It's in a 2600 lb streetrod and I just used the basic package all the other guys seemed to use. I too thought about 500 cfm carb but others seemed to use this 600 cfm combo and it worked fine. The manfold is an Edelbrock "Performer" dual plane idle-5500 RPM suggested for this engine. Vacuum secondary, mild stock cam. I'll check the rods and different holes suggested above and peer down the throat to check fuel and report back here.
Ove time I have tried to fix this and I have altered the timing and did get it to run better with changes. Before that I got it to run better with a bigger air filtler (10" x 3") and it does run better as the engine gets hotter. I think I'm now going in the right directon with one of htese suggestons and will look further tonight .

 

[skargo]

I'm actually thinking of removing my 1406 for a properly built q-jet in my Pontiac 400.
I still have an occasional bog, but much better than what it did with the stock accel pump.