Demon carb advice!
Thread Starter
Instructor
Joined: Nov 2004
Posts: 194
Likes: 0
From: Appleton Wi.
Demon carb advice!
I have been having trouble with hesitation on acceleration from a stop. Setting-up the carb numerous times from the instructions, and trying different settings and parts. All to no avail. I finally broke down and called the tech. The tech guy told me that the instructions need to be updated. Even things like the idle adjustment aren't close to what they should be.They have been coming out with new products and havn't had time to do updates to existing instructions. Anyhow, he told me something to try, change the gasket to a 4-hole style, rather that the recommended large square hole design. It solved all my problems. I commend the tech service guy, but would sure like to see better instructions. Hope this helps somebody else.
TJ
TJ
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
If you install a four hole gasket in an open plenum your going to have a bit of a problem. 
However, a four hole spacer does increase the throttle response. I use a four hole 1/2" spacer with my Mighty Demon 750 on the street and a 2" four hole contoured spacer on the track. Throttle response is still very crisp with the 2" spacer.
However, a four hole spacer does increase the throttle response. I use a four hole 1/2" spacer with my Mighty Demon 750 on the street and a 2" four hole contoured spacer on the track. Throttle response is still very crisp with the 2" spacer.
Thread Starter
Instructor
Joined: Nov 2004
Posts: 194
Likes: 0
From: Appleton Wi.
The tech guy told me that the carb sitting off the divider in the manifold could be causing reverberation from left side to right. He was correct. Open gasket for open plenum....4-hole for divided style. simple as that!!
TJ
TJ
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I guess that wouldn't work on a RPM style manifold where they cut the center divider down to improve high RPM power ?
There is still a possibilty the new gasket solved the problem just from being new, never re-use a carb gasket from one carb to another. The carb will make an imprint of it's base in the gasket and if you change to a different carb and use that gasket you will not get a good seal and could have the same hesitation problems you described
There is still a possibilty the new gasket solved the problem just from being new, never re-use a carb gasket from one carb to another. The carb will make an imprint of it's base in the gasket and if you change to a different carb and use that gasket you will not get a good seal and could have the same hesitation problems you described
Last edited by MotorHead; May 11, 2005 at 08:38 AM.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Originally Posted by TJ76
Yeah,
High rpm power wasn't the problem I was having. Only accelerating from a stop.
TJ
High rpm power wasn't the problem I was having. Only accelerating from a stop.
TJ
If this is the case then I think everyone with an RPM style intake would have a similar problem because as I stated the center devider is cut down down about 1/8 of inch so the carb will never seal here. You did not say whether you reused the old gasket when you put the Demon carb on ? Kinda doubt you did though as new Demons come with new gaskets.
I was just a skeptical of the answer as I had never heard of this reverberation problem before, doesn't mean it does not exist. Whatever has happened to solve your problem resulted from a recommendation from the tech guy and he should be commended I am glad the problem
is solved
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Thread Starter
Instructor
Joined: Nov 2004
Posts: 194
Likes: 0
From: Appleton Wi.
Yeah,
I needed a 1/4" spacer for the carb to fit over vacuum fitting. But a recommended one. And it was sealing correctly. Why the difference with this. and not an rpm? It seems similar, but weird things happen. It's probbaly engineered to work that way. Maybe because of the more blended apperance of the top of the divider, versus the flat top of my manifold! Only a guess. But anyhow, I was having the same problem with my q-jet, thinking the Demon would help to solve my problem. Now I'll try the q-jet with a divided gasket and see if it is better than what it was before. I think that would tell me if that was definately the problem.
TJ
I needed a 1/4" spacer for the carb to fit over vacuum fitting. But a recommended one. And it was sealing correctly. Why the difference with this. and not an rpm? It seems similar, but weird things happen. It's probbaly engineered to work that way. Maybe because of the more blended apperance of the top of the divider, versus the flat top of my manifold! Only a guess. But anyhow, I was having the same problem with my q-jet, thinking the Demon would help to solve my problem. Now I'll try the q-jet with a divided gasket and see if it is better than what it was before. I think that would tell me if that was definately the problem.
TJ
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
Interesting, when I installed a cold air box in my hood, I had to use a 1" spacer to get the height right. The spacer I happened to have was a four hole piece from another project. I noticed much better throttle response and the slight tip in stumble I'd been chasing was gone...this is on a 4150 Holley
