Can someone define a carb "bog"?

 

i'm not 100% sure but I belive (sp?) it refers to too much fuel.

 

"bog" means you hit the gas pedal, and the car decides it doesnt wanna go right now.

 

A good rule of thumb when it comes to carbs: almost all bogs are lean bogs. In other words, if she bogs and then hauls butt, it's almost always becuase it went lean, not rich.

 

I agree with Damon. The throttle blades open and "dumps" more air into the engine than the engine neads, hence, leaning it out.

 

Well, I'll disagree with the details, and try to describe what's happening in the carb.

"Bog" is a momentary loss of power, typically when the secondaries open, when the secondary metering circuit fuel flow has not begun (because it hasn't been needed) but the throttle blades are open and allowing air flow. So, as Damon stated, it's a lean condition.

With mechanical-only secondaries, an additional accelerator pump is used to make up for the lack of fuel flowing in the metering circuit (double-pumper carbs). As fuel is pulled through the circuit as the vacuum is created in the venturi, the system "rights" itself. If you have a bog situation with one of these carbs, you either need to tune the secondary accelerator pump, or the carb is too big for the engine, or you are going WOT at too low of RPMs (too little stall with an automatic transmission).

In vacuum secondary or air valve secondary systems, the air flow is brought on gradually so the fuel can be drawn into the metering system. They accomplish it in different fashions, but the intent is to get the fuel flowing before the air flow is allowed to go to the maximum. If you have bog with one of these carbs, you've got some tuning to do.

 

Hello,
I have a question about bog..
I know this thread is old but maybe you could help me out?

At highway speed tonight around 55 I went WOT and bogged
I did smell a strong odor of a rich condition.
My questions.
I routed the pcv hose to the small port in front
of the carb which was capped.
If this is incorrect should I run the pcv to the intake manifold
instead?
The pcv wasnt hooked up so Im not sure where it should go.

I have 2160 holley vacumm secondaries.
When I gradually advance the throttle theres no problem
But then again I never go to WOT.

 

PCV should be the large port in the carb base (in back). You don't want to run it to a manifold port, as that would only go to a couple of runners, and you want the PCV flow shared by all of the cylinders.

Sounds like you need a stiffer secondary spring. Either that, or you've got a gross problem in the secondaries.

 

The large port on back of the carb is being used
for the brake booster.
I will route the pcv to the air cleaner assembly
and see if this corrects the problem.
I purchased a carb book for the holley .
I will look into the secondary system
thankyou
Dave

 

Run the brake booster vacuum line to the manifold. Use the carb port for the PCV. Going to the air cleaner won't do a lick of good.

 

oops

thanks for the help!

I routed the pcv to the intake manifold for now
because I dont have the right hoses to replace the
booster line, the intake manifold vacumm outlet is smaller
then 3/8.
I then routed a hose from the passenger valve cover to the
air cleaner.
The idle is smoother then before.
But she still will bog if I go wot.

2 weeks ago I had to adjust the idle screws
because she would backfire through the carb and started
to idle poorly when I went richer with the idle it smoothed
out and didnt backfire anymore.

I am going to purchase the holley vacumm secondary spring
kit and distributor advance spring kit
from summit or jegs and do some experimenting.

I will also advance the timing a bit more
right now she is at 6 degrees.

 

Rather than the secondary spring kit, the Quick Fuel adjustable secondary housing is the way to go (available from Jegs, not sure about Summit). Instead of varying the closing force that the vacuum signal has to overcome, the Quick Fuel setup allows you to adjust the vacuum signal itself. Much better approach.

 

Yeah it looks cool also.

So if I go wot at any speed and bog
I could adjust the secondary vacumm
with a turn of a screw.. sounds easy enuff.
hope it works.

 

Question right here, I have the same exact problem with my stock quad. It bogs as soon as the secondaries open. it takes off on 3 quarters. I can litteraly count to 2 or 3 b4 the car moves. and i get a strong smell once it gets going. Someone help me on fixing this problem, ive had it as long as ive had the car, and i havnt been able to fix it. Anyone kno how to fix it???

 

AKA "quadrabog".

1) Make sure the choke pull-off vacuum diaphragm is intact, working, and the link to the secondary air valve is there.

2) Adjust the secondary air valve tension spring. There's a tech article describing it linked on the TGO homepage.