Wide open: throttle bog
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From: S. Mississippi
Wide open: throttle bog
Been trying to diagnose a WOT bog condition on my truck. Got the timing set spot on, pulls a solid 20" of vac at a very smooth idle. I've watched some of the Holley tuning videos on YouTube, but still haven't quite figured out exactly what my truck needs.
When I nail the throttle from cruise it just chokes down and damn near stalls unless I let off. Kinda scratchin' my head on this one.
FYI: Holley 4150 Vac secondary 600cfm.
Edit:
I took the vacuum secondary apart a few minutes ago, to see what spring was in it and maybe figger out if I need to step up to a heavier spring for the truck. Turns out I've got a black short spring in there, which IIRC that should be the heaviest spring that holley has. Maybe I'm not getting enough pump shot, or I need to step down to a lighter spring so that it'll act right.
I'm still confused here, guys any help would be appreciated.
Just to give an idea of the spring I"m looking at in my secondaries it is the short black spring in that picture. http://holley.com/data/products/pictures/large20-13.jpg
When I nail the throttle from cruise it just chokes down and damn near stalls unless I let off. Kinda scratchin' my head on this one.
FYI: Holley 4150 Vac secondary 600cfm.
Edit:
I took the vacuum secondary apart a few minutes ago, to see what spring was in it and maybe figger out if I need to step up to a heavier spring for the truck. Turns out I've got a black short spring in there, which IIRC that should be the heaviest spring that holley has. Maybe I'm not getting enough pump shot, or I need to step down to a lighter spring so that it'll act right.
I'm still confused here, guys any help would be appreciated.
Just to give an idea of the spring I"m looking at in my secondaries it is the short black spring in that picture. http://holley.com/data/products/pictures/large20-13.jpg
Last edited by desperado_18_2000; May 31, 2011 at 03:34 PM. Reason: added a pic
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Posting Guru
Joined: Jan 2001
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From: S. Mississippi
Nope, this one only has a single accel pump on the front bowl. I did however find out something else while tinkering today, that my accel pump has a white cam installed in the first slot/hole. I bumped that up to the second hole, and how instead of stalling entirely it will hesitate for a split second and then rev up.
I'm thinking I still might need a change of secondary spring, and perhaps a cam set, and while I'm at it I might need to change the accel pump itself.
I'm thinking I still might need a change of secondary spring, and perhaps a cam set, and while I'm at it I might need to change the accel pump itself.
Laughing Gas
Joined: Feb 2010
Posts: 781
Likes: 8
From: Sanford, NC
It still sounds like the accel pump. Try a green cam first installed in the first hole and
see how it does. If it still has a bog try the second mounting hole and test again. You
might use the next lightest spring in the secondary vacuum but that wouldn't affect
the bog unless your carb is way too lean. Do one thing at a time and see what difference it
makes and then move on to other changes one at a time. Good Luck.
see how it does. If it still has a bog try the second mounting hole and test again. You
might use the next lightest spring in the secondary vacuum but that wouldn't affect
the bog unless your carb is way too lean. Do one thing at a time and see what difference it
makes and then move on to other changes one at a time. Good Luck.
Last edited by ctubutis; May 31, 2011 at 07:46 PM. Reason: fix line breaks
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Joined: Nov 2007
Posts: 22,415
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From: Denver Metro Area, CO
It still sounds like the accel pump... You might use the next
lightest spring in the secondary vacuum but that wouldn't affect
the bog unless your carb is way too lean. Do one thing at a time
and see what difference it makes and then move on to other
changes one at a time. Good Luck.
lightest spring in the secondary vacuum but that wouldn't affect
the bog unless your carb is way too lean. Do one thing at a time
and see what difference it makes and then move on to other
changes one at a time. Good Luck.
I'd also be pokin' around the accelerator pump area.
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