Please help me find this bog...

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LXguy

LXguy

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Hey All:

I have a bog in my car I can't seem to tune out.

I leave off a transbrake and the thing goes, then bogs, then goes. Sometimes it turns the tires a bit when it picks up again.

I've tried less burnout, more tire pressure, two step adjustements, and adjusting the cal tracs and rear shocks. None of this made much of a difference if at all.

I'm starting to think its in the carburetor - because the one time the car has left "perfect" - I was at the tree and I ended up letting out of it because the tree wasn't coming down, then it did,so I just went back up on the gas (extra pump shot)and released as soon as the car came up to RPM. A buddy who was watching the car said, it spat out a bunch of black smoke, but left like he hadn't seen it before. This makes me think it might be leaning out when I release the button and it loads?

The carb is a 750 Quickfuel double pumper. It has a power valve in the front (8.5), and a plug in the back. I am running a wideband O2. Jetting is 73/77, which gets me around 13.00 at the top end of the track and about 14.00 on part throttle cruise. I typically leave the line at 3200 RPM.

Any ideas/help are appreciated.

Thanks,
Steve
 
i don't know squat about a trans brake but i do know this
if a car bogs right away you have too much carb
if it takes off then bogs you don't have enough go up on the jets then read the plugs
 
I suggest bigger jets, sounds like there to much air and not enough fuel. It is a cheap try.
 
I ran 73-74/82 in my proform 750, thats really all a quickfuel carb is, thats what there carbs are based on, a PF main body, I think your going lean with that 77 jet, drop in some 82s out back & try again, THEN keep jetting up F&R untill the MPH slows, I think you'll make your best power at 12.6-12.8 WOT.
 
i wouldn't go up in jetting read the plugs,might just need a bigger rear pumpshot shooter.and jet extenders in the secondary side
 
using a brake your foot is on the floor and the pump shot is used up so you need to put more jet in it, it's starving for fuel. the hotrod showed you this when you flooded it with fuel. that's why it falls on it's face. just keep going to more jet until the bogs gone. go up he same amount front and rear and rear extentions like mentioned if you don't already have them.
 
make sure your timming is set right , and check plug s and put exstended jets in the rear. you might be pulling your fule away from the jets and make sure your floats are set up, becuse if not your bowls will run dry before the fuel pump can pick it up. whats your fuel pressure at are you running a tank or fuel sell mabe you are puttiing all you fuel at the rear of the tank and it cant get any till the car levels a little .??
 
Quickfuel used to use the proform main bodies, now they do their own.

The carb came with jet extensions in the rear. Floats are where Quickfuel says they want them. I've been running the car with close to a full tank of gas.

I guess it seems pretty obvious. Of course, The trick is I don't want to fatten it up so much to kill the bog that it doesn't make power on the top end of the track. I have arrived at this jetting from watching the wideband at the top of the track, dyno testing, etc.

I've got a mechanical fuel pump, so maybe that could be part of it also, though I've had faster cars that had no problem with a mechanical unit.

I'll try jetting it up a little this weekend and see what happens.
 
another thing you might look at is if the carb has replaceable air bleeds. you might just be able to use smaller ones in the idle/intermediate circuit to just richen that part up. apparently that's where it's falling on it's face. you seem to have the top side doing ok.
 
USUALLY a bog like you describe is in the pump shot. If it's something the car has just started, I would look at the pump diaphragm. It might be going out.
 
If you haven't already you may want to take a piece of hose and connect the vent tubes on the top of the carb, just remember to cut a hole at the top of the curve of the hose so the vents still work. Helps prevent fuel from sloshing up and into your carb.

Cheap fix, it may not solve a problem but it will prevent one!
 
The pump shot isn't the problem, he's out WOT with the brake, pump shot is meaningless, But from what he descibed when he let off & nailed it again & it did bogg but launched better is telling him it wants more fuel.

Steve, it won't hurt fattening it up, if it slows you'll know, just make a few 1/8 mile passes, It'll tell you, if your MPH picks up, then it wants more fuel
 
Dorian said:
If you haven't already you may want to take a piece of hose and connect the vent tubes on the top of the carb, just remember to cut a hole at the top of the curve of the hose so the vents still work. Helps prevent fuel from sloshing up and into your carb.

Cheap fix, it may not solve a problem but it will prevent one!
Click to expand...

This never hurts when you start 60ft'n hard.
 
I think I will try the rubber hose thing. Can't see as it could hurt anything.

Messing with the bleeds makes sense too.

Trying to contact Quick Fuel, but not having much luck.
 
Quickfuel seems to think it is a fuel pressure issue. They say my pressure is too high. I'm at 8 with a carter steet/strip mechanical pump. They say they want 6.5.

IF I can figure out a good way to do it (as in not run an extra four feet of fuel line off to a regulator and back to the bowls again) I'll try that first. Failing that I'll pursue the jetting/bleeds.

Steve
 
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