Holley off idle stumble
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 876
Likes: 1
From: Same as our leaders Out of my mind
Holley off idle stumble
I have a Holley 750 (#4150) on a freshly built 383 Stroker with a manual transmission. Sometimes I get a stumble or bogging situation off idle and up to about 2000 RPM. Sometimes the problem clears up by itself. I have checked for vacuum leaks, retorqued the intake manifold bolts, checked the fuel lines etc... with no obvious source for the stumble. When the trouble happens it makes it hard for me to maintain low cruising/idle speeds. It smooths out over 2000 RPM. Any ideas?
Thanks!
Thanks!
Racer
Joined: May 2003
Posts: 467
Likes: 10
From: NE Georgia GA
Originally Posted by icanfixitforyou
I have a Holley 750 (#4150) on a freshly built 383 Stroker with a manual transmission. Sometimes I get a stumble or bogging situation off idle and up to about 2000 RPM. Sometimes the problem clears up by itself. I have checked for vacuum leaks, retorqued the intake manifold bolts, checked the fuel lines etc... with no obvious source for the stumble. When the trouble happens it makes it hard for me to maintain low cruising/idle speeds. It smooths out over 2000 RPM. Any ideas?
Thanks!
Thanks!
I can't really offer any help, but I have a 650 cfm Demon carb (uses a Holley center section) that has the same problem. It's almost like the engine loses fuel for a second, then it surges and picks it back up.
Instructor
Joined: Dec 2004
Posts: 216
Likes: 1
From: Lapeer Michigan
You need a larger delivery nozzle.
For further explanation,
http://www.holley.com/TechService/Library.asp
On the site go to= Look inside your carb.
For further explanation,
http://www.holley.com/TechService/Library.asp
On the site go to= Look inside your carb.
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
Originally Posted by 1BAD80
You need a larger delivery nozzle.
According to your description. A stock 750 has a 31 primary shooter, try a 33, a 35 and then a 37 primary shooter and see which feels best. A larger shooter will give you greater initial fuel volume. If that helps you can play with different pump cams and locations to get the best response. You'll know if the 37 is too big because it will accelerate good then it will bog or hesitate, then go to the smaller ones.You should have a white pump cam (smallest capacity) in #1 position, if you put it in #2 position you'll increase initial delivery with less final fuel delivery. So the #2 spot may fine tune your bog even further. It's all trial and error but Holleys are the most tunable carb once you get the hang of it.
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Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 876
Likes: 1
From: Same as our leaders Out of my mind
The "shooter" size has already been increased. Today I drove the car with no problems, ran smooth and powerful like it should, of course my mechanic was in the car with me at the time, so it wouldn't dare do it then....
Thanks for your replies, I'll see what i can come up with.
Thanks for your replies, I'll see what i can come up with.
He is always driving the car also
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
Does your engine setup have a heat passage in the intake? If not, it will take longer than normal to warm up. I'm thinking the intermitent problem happens when its not been running long enough in the colder weather.
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 876
Likes: 1
From: Same as our leaders Out of my mind
Originally Posted by w1ctc
Does your engine setup have a heat passage in the intake? If not, it will take longer than normal to warm up. I'm thinking the intermitent problem happens when its not been running long enough in the colder weather.
I tried this avenue of thinking too, the problem is not related to hot or cold, highway cruising or local driving, dirt in the gas or over lean mixture. This is one of those stinking little gremlins that seem to have no rhyme or reason to them. Yesterday the engine performed flawlessly, go figure....
