Jetted holley now it bogs

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Hansen

Hansen

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Hello carb experts, i have a stock 360 in my d150 and have been driving it for a while, it has had slight dips while cruising but nothing major. I checked the plugs and they where really light so i jetted it up from 71 to 73. Now it bogs while i cruise. I can drive at 1/3 throttle and it bogs/hesitate for a second and gets back up. Also have alot of hesitation while rolling down hill with no throttle, but it has done this all the time. It is a 650 holley 4160 w/rear metering block.

thanks.
 
Are you sure that you have the correct power valve installed. The wrong power valve will give you a bog upon acceleration or just about anytime you hit the gas.
How To Tune The Power Valve In A Holley Carburetor

The accelerator pump also is designed to stop the engine from hesitating, Holley makes a variety of accelerator pump "cams" for different CCs (shots) of fuel and at different rates of flow:

QFT41-100__19730.1591897030.jpg
 
What RPM are you at for cruise? As I understand (as I'm working through issues with my Quick Fuel 650), is under ~2000 rpms the primary jet isn't in play yet and you're still on the transition circuit which sounds like it could be lean. Does it bog some starting from a stop?

Someone correct me if I'm wrong.
 
Last edited:
dano said:
What RPM are you at for cruise? As I understand (as I'm working through issues with my Quick Fuel 650), is under ~2000 rpms the primary jet isn't in play yet and you're still on the transition circuit which sounds like it could be lean. Does it bog some starting from a stop?

Someone correct me if I'm wrong.
Click to expand...
don't have an rpm gauge but guessing around 2-3k goin 50mph
 
Treblig said:
Are you sure that you have the correct power valve installed. The wrong power valve will give you a bog upon acceleration or just about anytime you hit the gas.
How To Tune The Power Valve In A Holley Carburetor

The accelerator pump also is designed to stop the engine from hesitating, Holley makes a variety of accelerator pump "cams" for different CCs (shots) of fuel and at different rates of flow:

QFT41-100__19730.1591897030.jpg
Click to expand...
will check what power valve i have.
 
If it didn't bog before, you went the wrong way.
 
Check the accelerator pump linkage.
If throttle move pump needs to squint gas
 
Treblig said:
Are you sure that you have the correct power valve installed. The wrong power valve will give you a bog upon acceleration or just about anytime you hit the gas.
How To Tune The Power Valve In A Holley Carburetor

The accelerator pump also is designed to stop the engine from hesitating, Holley makes a variety of accelerator pump "cams" for different CCs (shots) of fuel and at different rates of flow:

View attachment 1715726142
Click to expand...


That Holley link is dead wrong.

Just so it’s clear to the OP, you set your power valve opening 3-4 numbers below CRUISE vacuum. Never set your power valve opening at half of idle vacuum. It’s not correct, it was never correct and it will never be correct.
 
yellow rose said:
That Holley link is dead wrong.

Just so it’s clear to the OP, you set your power valve opening 3-4 numbers below CRUISE vacuum. Never set your power valve opening at half of idle vacuum. It’s not correct, it was never correct and it will never be correct.
Click to expand...

Check your messages please. Thank you drive through.
 
Too much transfer slot exposure?

"When the throttle blades are opened far enough at idle to uncover the transfer slots, this adds idle fuel that is not controlled by the idle mixture screws. This increases fuel flow making the idle air/fuel ratio extremely rich. Yet when additional throttle is added for light acceleration, the engine stumbles."
 
yellow rose said:
That Holley link is dead wrong.

Just so it’s clear to the OP, you set your power valve opening 3-4 numbers below CRUISE vacuum. Never set your power valve opening at half of idle vacuum. It’s not correct, it was never correct and it will never be correct.
Click to expand...

Revisiting this......because I have my QFT 450 off Vixen right now. It was kinda actin up stalling every now and then coming to a stop, like it has trash in it. Some "genius" cut part of the secondary float off?!?!? So, it has this ROUGH surface with tiny bits of black float material falling off the float into the bowl. Strange. Got another float on the way.

Anyway, what do you recommend when I get it back together? I will get a cruise vacuum reading and go from there. So 3 or 4 numbers below and why? How do I make that determination? Just guess? Thank you drive through.
 
yellow rose said:
That Holley link is dead wrong.

Just so it’s clear to the OP, you set your power valve opening 3-4 numbers below CRUISE vacuum. Never set your power valve opening at half of idle vacuum. It’s not correct, it was never correct and it will never be correct.
Click to expand...

Aight den. It was late when I took this thing apart. I "THOUGHT" I had it figured out why someone would cut that float, but it's still a mystery. Never seen the secondary side of a vacuum secondary carburetor WITHOUT a metering block have jets. This one does. It's made that way, too, as you can see the dimples in the metering plate under the jets. I thought at first, someone had modded it, and cut the float for jet clearance. However, putting the float bowl against the main body, I can see there's no need to cut the float. There's plenty of room. I'm going to pop the e clip off the front float and transfer it to the fear bowl to confirm, but I know it will. This is an unusual carburetor. I guess all of them are like this sans the cut float. Does anyone else here have one they've been into? It's a Quick Fuel 450 4160 vacuum secondary. I do have a new float on the way.

CUT FLOAT.jpg
JETS IN METERING PLATE.jpg
 
RustyRatRod said:
Aight den. It was late when I took this thing apart. I "THOUGHT" I had it figured out why someone would cut that float, but it's still a mystery. Never seen the secondary side of a vacuum secondary carburetor WITHOUT a metering block have jets. This one does. It's made that way, too, as you can see the dimples in the metering plate under the jets. I thought at first, someone had modded it, and cut the float for jet clearance. However, putting the float bowl against the main body, I can see there's no need to cut the float. There's plenty of room. I'm going to pop the e clip off the front float and transfer it to the fear bowl to confirm, but I know it will. This is an unusual carburetor. I guess all of them are like this sans the cut float. Does anyone else here have one they've been into? It's a Quick Fuel 450 4160 vacuum secondary. I do have a new float on the way.

View attachment 1715742951 View attachment 1715742952
Click to expand...
Looks like the Qft jet plate but not nearly as nice.
 
Stock primary jetting should be right for a stock 360. Power valve should be a 10.5
Orange cam might work, but the red is more likely and on the 2nd hole, shooter for automatic would fall into 31-35

That's where I'd start.
 
yellow rose said:
That Holley link is dead wrong.

Just so it’s clear to the OP, you set your power valve opening 3-4 numbers below CRUISE vacuum. Never set your power valve opening at half of idle vacuum. It’s not correct, it was never correct and it will never be correct.
Click to expand...
Correct. I have a 10.5 PV in mine, not what Holley's method would recommend
 
I always just keep dropping the PV size until the bog goes away. But that's only after I get the air/fuel, accelerator pump and pump cam correct.
 
Treblig said:
I always just keep dropping the PV size until the bog goes away. But that's only after I get the air/fuel, accelerator pump and pump cam correct.
Click to expand...
Yeah, it's hard when you don't know for sure if the op's know a rich bog from a lean stumble. If its 14" vac or better at idle in gear, 10.5 is as close as you can get.
 
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