speed demon carb
Thread Starter
Instructor
Joined: Jun 2001
Posts: 188
Likes: 0
From: nova scotia canada
speed demon carb
guys- have a 650 speed demon on my 400 horse stingray. The carb works well except that when you mash it to the floor there is no secondary kick. I know it's not a quadrajet with those big secondaries but there is no snap at all, it just gets louder.Any advise would be welcomed.
thanx wade
thanx wade
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
You can check it with mechanical, at rest engine turned off the front throttle plate when it hits a 45 degree angle the mechanical linkage should very quickly pull the secondary open the back accelerater pump squirt fuel as the back throttle plate begins to open. look to see if your throttle cable is slipping in its hold down. Check the fuel filter, fuel pressure.
Problem could be advance in the dist. silicon spray lubricant.
Problem could be advance in the dist. silicon spray lubricant.
Last edited by Little Mouse; Jul 4, 2009 at 01:46 PM.
Pro
Joined: Mar 2009
Posts: 703
Likes: 2
If it gets louder, it sounds like a bog.. When you first mash the pedal, your vacuum drops and your motor relies on pump shot from the squirters to recover so if your motor is getting a loud, it sounds like it could be getting to much shot.. You may have to play with different size squirters or cams to until you find the right combo.. Keep in mind a mech carb will dump fuel from both squirters when you mash the pedal and rarley are they perfect out-of-the-box...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Advanced
Joined: Apr 2009
Posts: 54
Likes: 0
From: Indianapolis Indiana
I use a 650 speed demon also.
I read somewhere, either in a tuning post, or in the speed demon documentation itself, that there should not be a secondary kick. I read that it should only be noticable on the track with decreased ETs. The document stated that if you are getting a kick, that the spring pressure is incorrect (come to think of it, it might be the document that comes with a Holley spring kit). I can dig up more info if you need it. My car does not noticably kick when I mash the gas, just nice smooth acceleration. One difference that comes to mind between the Qjet and Demon is that the Qjet actually has a mechanical linkage to open up the secondary butterflies (correct me if I'm wrong, but I think this is right), but the door to let the air in on top is vaccum operated. Before I replaced my qjet, that door opened very quicky (probably too quickly) and I got that kick. Since the Demon butterflies open slowly, I would imagine that kick is not a good thing.
I read somewhere, either in a tuning post, or in the speed demon documentation itself, that there should not be a secondary kick. I read that it should only be noticable on the track with decreased ETs. The document stated that if you are getting a kick, that the spring pressure is incorrect (come to think of it, it might be the document that comes with a Holley spring kit). I can dig up more info if you need it. My car does not noticably kick when I mash the gas, just nice smooth acceleration. One difference that comes to mind between the Qjet and Demon is that the Qjet actually has a mechanical linkage to open up the secondary butterflies (correct me if I'm wrong, but I think this is right), but the door to let the air in on top is vaccum operated. Before I replaced my qjet, that door opened very quicky (probably too quickly) and I got that kick. Since the Demon butterflies open slowly, I would imagine that kick is not a good thing.