4 speed bog off the line...help

[3rdelke]

We finally got our bb, dual quad stroker to the track, seems as if irrespective of rpm, huge bog leaving.can you have to much grip, 10.5 inch slicks barely slip, 4.10 Dana. Any ideas? Thanks, Bob and Kevin

 

[lewtot184]

sounds like a tune-up issue, carb modification problem, lack of fuel, or too much fuel pressure.
i run a ch28 on a 440 with 3.23 gears and stock converter and it wouldn't bog if superman was holding on to the rear bumper.

 

[PurpleBeeper]

My first guess is to add stiffer secondary springs if running vac. secondary carbs and/or increase the squirt.... bigger cam, accelerator pump, bigger squirter holes.... but if you go that route, move up the squirt a tiny bit at a time. You can get way to rich really quick. I'd probably suggest stiffening the springs as a first step. (if Holleys)

 

[eldubb440]

lol...... you need to ride the clutch like a bicycle

 

[3rdelke]

Thanks, guys, should have mentioned running a pair of 750 edelbrocks . Read somewhere that fuel sloshing or something about primary bowl vent, but think they were referring to holleys.wonder what rpms guys are leaving?

 

[3rdelke]

My first guess is to add stiffer secondary springs if running vac. secondary carbs and/or increase the squirt.... bigger cam, accelerator pump, bigger squirter holes.... but if you go that route, move up the squirt a tiny bit at a time. You can get way to rich really quick. I'd probably suggest stiffening the springs as a first step. (if Holleys)

My first guess is to add stiffer secondary springs if running vac. secondary carbs and/or increase the squirt.... bigger cam, accelerator pump, bigger squirter holes.... but if you go that route, move up the squirt a tiny bit at a time. You can get way to rich really quick. I'd probably suggest stiffening the springs as a first step. (if Holleys)

Mech linkage, may try springs, guy from our local club said it's all in the springs. Thanks

 

[lewtot184]

Thanks, guys, should have mentioned running a pair of 750 edelbrocks . Read somewhere that fuel sloshing or something about primary bowl vent, but think they were referring to holleys.wonder what rpms guys are leaving?

hopefully nobody took the secondary velocity valves out. i'd look at float level and fuel pressure. float level too high in combination with too much pressure can cause an over rich condition. under hard acceleration the floats will drop with those carbs and when combined with a little too much pressure the floats loose control of the fuel flow. other things to look at is ignition curve and total timing. too much cam for the rest of the parts? maybe borrow and try a narrower tire to rule that out.

 

[3rdelke]

hopefully nobody took the secondary velocity valves out. i'd look at float level and fuel pressure. float level too high in combination with too much pressure can cause an over rich condition. under hard acceleration the floats will drop with those carbs and when combined with a little too much pressure the floats loose control of the fuel flow. other things to look at is ignition curve and total timing. too much cam for the rest of the parts? maybe borrow and try a narrower tire to rule that out.

 

[3rdelke]

Thanks, when my son comes home around Xmas time, first thing we are going to do is put it on a dyno , we may put street tires as well. We are running a stock cast intake, that may be a factor. Btw, the compression ratio is about 13 to 1,race fuel only

hopefully nobody took the secondary velocity valves out. i'd look at float level and fuel pressure. float level too high in combination with too much pressure can cause an over rich condition. under hard acceleration the floats will drop with those carbs and when combined with a little too much pressure the floats loose control of the fuel flow. other things to look at is ignition curve and total timing. too much cam for the rest of the parts? maybe borrow and try a narrower tire to rule that out.

Lew, we turned our fuel pressure down before we tested it to 4lbs

 

[hangn0ut]

Flywheel? Car weight? Assume stock ratios in the trans.

 

[Lionized]

13:1 and factory cast intake?
Maybe start there.

 

[Cornpatch MO]

My bet is, you are getting to much fuel at once. Just a thought to test as I have never run multi carbs, but can you shut down one carb so running on just one? Eliminate the simple stuff before you start throwing money at it. ..............................MO

 

[lewtot184]

Thanks, when my son comes home around Xmas time, first thing we are going to do is put it on a dyno , we may put street tires as well. We are running a stock cast intake, that may be a factor. Btw, the compression ratio is about 13 to 1,race fuel only

Lew, we turned our fuel pressure down before we tested it to 4lbs

4lbs? at idle/cruise or WOT? if it's not too much fuel then it has to be too much air; like the velocity valves in the secondaries are missing,.....? i've run the pressure a little high with my 600's without any problems but do run a return line.

 

[AR67GTX]

The accelerator pump height is pretty critical on Edelbrocks. The accelerator pump well fills from a v-notch in the topside, leading to the left side float bowl. If the rod height isn't carefully set so that the rubber cup rises above that v-notch, you don't get fuel inside the well, and when the throttle is punched it gets a weak shot of fuel - and it will bog. I have the 800 Edelbrock on my GTX and after pulling it apart and carefully measuring everything, I had to bend the linkage a lot to raise the accelerator plunger up high enough to fill the well - much higher than Edelbrock's specs. And this was with a brand new accelerator pump specific to my carb. Before, any opening of the throttle resulted in a hesitation or bog. I had to pussy-foot the throttle to take off smoothly. After getting it correctly adjusted I can just nail it from a dead stop and it instantly responds and lights up the tires now.

It may have nothing to do with your situation but something you might check.

 

[lewtot184]

The accelerator pump height is pretty critical on Edelbrocks. The accelerator pump well fills from a v-notch in the topside, leading to the left side float bowl. If the rod height isn't carefully set so that the rubber cup rises above that v-notch, you don't get fuel inside the well, and when the throttle is punched it gets a weak shot of fuel - and it will bog. I have the 800 Edelbrock on my GTX and after pulling it apart and carefully measuring everything, I had to bend the linkage a lot to raise the accelerator plunger up high enough to fill the well - much higher than Edelbrock's specs. And this was with a brand new accelerator pump specific to my carb. Before, any opening of the throttle resulted in a hesitation or bog. I had to pussy-foot the throttle to take off smoothly. After getting it correctly adjusted I can just nail it from a dead stop and it instantly responds and lights up the tires now.

It may have nothing to do with your situation but something you might check.

i had to remove a bunch of casting flash and lowered the v-notch a little on a 800 to get the plunger in a more favorable position. i also reduced the squirter size, main metering jet size to get a good crisp tip-in.

 

[Cornpatch MO]

i had to remove a bunch of casting flash and lowered the v-notch a little on a 800 to get the plunger in a more favorable position. i also reduced the squirter size, main metering jet size to get a good crisp tip-in.

It can be a little confusing . It can come from both to much fuel suddenly, or to much air sudenly................................MO

 

[AR67GTX]

It can be a little confusing . It can come from both to much fuel suddenly, or to much air sudenly................................MO

Technically true - but, I learned long ago that the vast majority of initial throttle-opening bogs are the result of a lean condition (not enough fuel). If by chance he is dealing with a rich condition (not enough air) he should know so due to black smoke blowing out the tailpipes until air flow catches up to fuel.

Fuel pressure at 4 lbs sounds a little low. Shouldn't it be more in the 5 to 5-1/2 lb range?

 

[Valhalla083]

Thanks for all the advice! I was advised to keep the fuel pressure around 4-4.5lbs to avoid bending the floats. We had that problem initially and that seems to have been resolved. I agree its either too much air or too much fuel. It seems to me that more people suffer from a rich condition than lean.. It is easy to tell the car has had a rich condition for some time, but we have changed the carburetion around so much, its hard to know. I'll check about the accelerator pump, this seems promising.

 

[Cornpatch MO]

Thanks for all the advice! I was advised to keep the fuel pressure around 4-4.5lbs to avoid bending the floats. We had that problem initially and that seems to have been resolved. I agree its either too much air or too much fuel. It seems to me that more people suffer from a rich condition than lean.. It is easy to tell the car has had a rich condition for some time, but we have changed the carburetion around so much, its hard to know. I'll check about the accelerator pump, this seems promising.

A good easy starting point. let the engine fully warm up. At idle, manually and suddenly , give it full throttle at the carb linkage. If it momentarily bogs or hiccups before the RPM come up, you have a lean or rich fuel condition . Usually rich if the carb is to big on the primary jet size ......................................MO

 

[3rdelke]

I'm trying to understand how the accelerator pump could cause a stumble of the line when the throttle is held steady for a 4 speed launch