650 Speed Demon question
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
650 Speed Demon question
ok..i got the Speed Demon on the motor today..i was wondering how you guys run a throttle cable bracket to support the cable...and any suggestions on how to hook up the spring return linkage and what cable bracket to use? i'd like to still use my stock throttle cable if at all possible. thanks.
Drifting
Joined: Jun 2000
Posts: 1,955
Likes: 2
Re: 650 Speed Demon question (REDSHARKONBOYDS)
Yeah, this was the biggest issue I ran into when installing Demon carbs on Chevy engines.
What we wound up doing was buying a Mr Gasket or similar GM throttle cable bracket at the local parts house. This includes the square opening to capture the stock throttle cable, and has a little hole at the bottom for hooking up the stock throttle return springs.
Now, these are designed for Holleys, which have SQUARE edges on the mounting base, the Demons are ROUND. So we took a small drill bit and drilled a hole in the bracket and the carb base to allow a roll pin to be tapped in. This prevents rotation, and the bracket is held in place vertically by the carb mounting stud.
Don't have a picture handy, but this worked on my '74 Corvette (small block) and my '76 Suburban (454) both with Speed Demons.
Yes, I know it sucks to drill a hole in a brand new $400 carb, but it's the only way I've done it. I hear you can buy a bracket from Edelbrock that mounts to their intakes...never did it.
Jeff
What we wound up doing was buying a Mr Gasket or similar GM throttle cable bracket at the local parts house. This includes the square opening to capture the stock throttle cable, and has a little hole at the bottom for hooking up the stock throttle return springs.
Now, these are designed for Holleys, which have SQUARE edges on the mounting base, the Demons are ROUND. So we took a small drill bit and drilled a hole in the bracket and the carb base to allow a roll pin to be tapped in. This prevents rotation, and the bracket is held in place vertically by the carb mounting stud.
Don't have a picture handy, but this worked on my '74 Corvette (small block) and my '76 Suburban (454) both with Speed Demons.
Yes, I know it sucks to drill a hole in a brand new $400 carb, but it's the only way I've done it. I hear you can buy a bracket from Edelbrock that mounts to their intakes...never did it.
Jeff
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
Re: 650 Speed Demon question (no_radio)
jeff, i think i'll go with your idea....btw, how do you like your Speed Demon?? have any tuning problems or any noticable differences in performance?
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: 650 Speed Demon question (REDSHARKONBOYDS)
I use a lokar cable and CSI bracket. They also make a Holley bracket just like it from Jegs. At least I think it's a Holley?
Drifting
Joined: Mar 2001
Posts: 1,896
Likes: 0
Re: 650 Speed Demon question (no_radio)
LOL..Yeah, Jeff really didn't want to drill a hole in the base of his carb. But, it was the only Idea I had. We even tried welding some funky bracket together. But that didn't work. But, the dowel in the base worked like a charm.
That's probably the least expensive way to go about it.
-Aaron.
That's probably the least expensive way to go about it.
-Aaron.
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: 650 Speed Demon question (1979toy)
The Edelbrock bracket bolts to the last 2 manifold bolts, no drilling required. I did have to do some modifaction on the bracket but not the carb. I just hooked the spring on the bracket.
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Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
Re: 650 Speed Demon question (Paul 75 L82)
Paul, can you give me the part# for that edelbrock bracket?? i have vortec heads too, so its got kinda of a different manifold set up with the bolts....think it will still work? thanks
Drifting
Joined: Jun 2000
Posts: 1,955
Likes: 2
Re: 650 Speed Demon question (REDSHARKONBOYDS)
jeff, i think i'll go with your idea....btw, how do you like your Speed Demon?? have any tuning problems or any noticable differences in performance?
I liked the 650 so much I bought a 750 vacuum secondary for my Suburban. Same deal, QJet was getting old (30K since rebuild) and was acting up. Instantly ran better, and idles better than it ever has. I shaved two full seconds off my 0-60 (vs QJet running crappy, it used to be faster). Haven't driven it enough to check fuel mileage, hoping to gain an MPG or two. Also haven't tuned this one, except to change the secondary spring, which takes about 2 minutes and took the last .4 seconds off my best 0-60.
I think you'll be happy.
One quick note...in the instructions I read BG talks about having both front and rear butterflies open equally. This is typically only true if your engine idles above 1000 RPM. I had both open and was WAY too rich at first. Closed rears, nice idle now. ALso, their tech line has been really helpful, don't be shy about calling with questions.
Jeff
