bogging problem

[Guest HALLOWEEN Z]

I ran my car tonight and ran 14.2 at 92mph and 60 ft. was 2.0. Thats a completely stock internals 350 and crappy tires. I have a 500cfm edelbrock with performer rpm intake, headers. I'm having trouble with my car bogging, exactly the feeling like its starving for fuel. I'm getting fuel to the carb and float bowls are adjusted correctly. Never happens except for at the track it will bog at different times, usually in first and second but sometimes 3rd. Sometimes its so bad I will let off and get back on and it does it again. Seems to get worse the bigger burn out I do? Everytime I drive past the water box or do a small burnout it won't do it at all. I'm thinking the fuel may be boiling in the carb. Could it be the carbs to small or the jets are wrong? Also my idle is fine for daily driving but after my first run it falls and I have to adjust it to 1100 in park to keep it from dying after I let off the gas on my burnout. It was still fun though, there was a 12.59 civic there that was not rice (rust bucket) very surprised, running nitrous of course.

[Guest tony78_280z]

I've had similar problems with my holley. Only on the throttle when moving the blades from mostly closed to mostly open, which I think is what you are doing while shifting with a manual tranny. I have an automatic, so only press on the gas once, but there is a definate bog. I even upgraded to a 50cc pump to get it to quit doing this.

 

Yes it could be the carb is too small. 500 is a bit lean for a 350. Yes it could be the wrong jets, as when you quickly open the throttle blades you are momentarily starving the motor for gas. You might need to upgrade to a more powerfull accelerator pump.

 

But !

 

Here is an interesting story. This happend to me just the other day, and it made me ponder... Other problems with my Holley forced me to put a quadra on for a few days. Magicaly, the bog went away. I pointed my finger at the Holley and cursed it for junk. I then went to setting the quadra idle screws. I turned them all the way in (motor died promptly at an idle which is what it should do.) And then turned it a turn and a half out which is "A good place to start from." And low and behold, it bogged on the throttle. Another full turn and the bog went away. Now with 1 and 1/2 turns it idled good, but at 2 and 1/2 turns the throttle lever didnt' even touch the adjustment screw and sometimes idles high. Sound familiar? The second to the last sentence leads me to think you have a similar problem.

 

Disclaimer: I have yet to put the Holley back on and turn up the idle scews to see if the bog goes away on it. That is my project tomarrow. Also I don't know if this will make it idle rich, or run rich through any other part of the carb's fuel systems.

 

 

Good Luck, and keep me posted (no pun intended) as I'm looking for a solution to this problem as well.

[Guest HALLOWEEN Z]

I've got an automatic(700r4), sorry left that out.

[Guest tony78_280z]

Today I toyed around with my carb again and experimened with other possible solutions to my bogging problem. I put the old 30cc pump back on and verified that there were no vacuum leaks None of this helped any, it still bogged. I then thought about how small the primarys are on a quadra jet and on a wim, moved my choke to about 3/4 position. Even with the 30cc pump, the bog went away.

 

My choke is a mechanical type. Full closed it clicks and locks into place, Fully open it clicks and locks into place. In between the choke can be set to any location, but there is a spring-like tension that allows the choke to move a bit depending on air flow and vacuum in the primarys. As I threw open the throttle I could watch the choke blades open and close with the throttle. With the choke set in between the full open of full locked locations the carb runs great with no bog.

 

Two things struck me as possible solutions.

 

One my choke is not functioning properly. It is not supposed to lock open or closed and is suposed to help richen or lean the mixture depending upon the air flow and the movement of that spring. My Haynes book barely mentions manual chokes but goes into great depth into the various automatic type chokes. Somehow I doubt this is the situation.

 

Two my carb is running lean. As I changed the jets on the carb (down 5 steps) the over all performance of the carb improved. Excepting the bogging. It allways did that. Even 5 steps up. So perhaps I improperly set my floats. I set it to where If I bump the car slightly with my hip the bowl sloshes and a little gas comes out the peep hole. I observed this technique once, and am now doubting if it is correct. Again, my Haynes book does a great job of describing tear down and rebuild of Holleys. It also has a great in depth discussion on functions of the various systems in a carb. It does not describe proper bowl setting.

More info tomarrow as I increase the floats.

[Mike C]

Bog is almost always because too much air is injested in the motor.

 

By enrichening the idle mixture, you minimize how much pump shot is required to hide the "bog".

 

The accelerator pump is the tool used to cover this. The extra fuel stabilizes the motor until fuel can start flowing through the primary metering circuit. On a Holley you can change pump cams & squirters to increase the shot. You can also take the existing cam and move the screw to the second hole which will speed up the rate at which the pump shot is delivered. Make sure that the gap between the pump arm and diaphragm lever is adjusted correctly as well.

 

 

The 30cc pump should be sufficient for just about anything. My 1040 cfm stage 3 BG 750 only has dual 30cc pumps.

 

On a Q-jet, you can slow the rate at which the air doors open. This allows the existing pump shot to be sufficient to cover the "hole".

[Guest tony78_280z]

The accelerator pump is the tool used to cover this...change pump cams & squirters to increase the shot. You can also take the existing cam and move the screw to the second hole...the gap between the pump arm and diaphragm lever is adjusted correctly as well...The 30cc pump should be sufficient for just about anything...

 

Yeah, I tried messing with all that. (except the moving the cam to another hole. I never could get the cam to line up right on a different hole. ) I even upgraded to a 50cc pump for extra gas. None of this had any real effect on the bog. The 50cc pump helped a bit, but the bog was still there.

 

My goal for yesterday was to adjust the floats. I had been setting it so that gas leaks out the sight plug when I bump the car with my hip. I raised it a bit so that the gas slowly leaks out constantly and it realy sloshes when I bump it. This is quite messy and I need some of those clear sight plugs.

 

The bog went away completely by raising the float level just a tad. I'm not sure if I was setting the floats wrong before. It ran great yesterday, and I plan to take it for another drive today. If it still don't bog then I'm scratching the Holley off of my list of stuff to fix.

[Guest HALLOWEEN Z]

I took the 600cfm carb off my friends car tonight and it still bogged the same. Theres no way it could be in the tranny could it? Could it be the fuel pump pressure because it squirts fuel well and its a new 5psi pump. But it does it in 1st gear sometimes and the float bowls wouldn't empty that fast would they? This is driving me crazy because I think I can get in the high 13's if I could just find the problem. I've ran out of gas before and the feeling and sound is just like that.

[Zoldman]

If you have one of the Edelbrock Quadrajet type carbs, the most likely culprit is the spring tension on the secondary air door. If the spring is too loose, when you jump on it, the door opens too quickly and causes the engine to go real lean, giving you the infamous "Quadrabog".

 

If you keep your foot in it, the bog goes away as the engine spools up, but all of your momentum is killed.

 

You also might have incorrect primaries and a too lean secondary rod set.

 

If you know the model number, I will see if I can find you a set up guide for your carb that can help you get it right. Give me as much info as you can.

 

The Quad is a great street carb if it is set up right; better than the Holley in my opinion for dual purpose (both street and strip) use.

 

Good Luck,

 

Bill

[Mike C]

Changing cams changes the rate at which the shot is delivered, and changing to the larger pump changes the amount available. But the shooter is what determines the volume of pump charge delivered. If you haven't changed shooters, that is your best bet. If you have a tiny shooter, you aren't using all of the 30cc shot, much less needing the 50.

[Guest HALLOWEEN Z]

I'll try messing with the secondary opening and the accelerator pump some more. I'll also get the model number or jetting of the carb tomorrow, mine is just an edelbrock 500 performer carb from jegs(brand new). My friends carb is either a 625 or 600, its a performer edelbrock to. It runs great on his 350 but he has vortech heads and a cam, not really radical cam but a good sounding idle. Mine is all stock internals with some kind of junk heads. I've got an edelbrock performer rpm intake and headers. I also noticed when I felt my coil it was a little warm (not real hot just warm) is this normal?