Holley W/ Mechanical Secondaries...Advice?
Thread Starter
Instructor
Joined: Sep 2008
Posts: 200
Likes: 6
From: Palmer, Alaska
Holley W/ Mechanical Secondaries...Advice?
Hey Guys,
I have a holley with mech secondaries on my 454 and am having trouble getting them to open all of the way. I don't have enough throw on my accel. linkage to get all four barrels 100% open. Does anyone know if there is a different ratio secondaries linkage that would allow them to open with a shorter cable throw. Anyone run into this or have any guesses. My accelerator pedal is in good shape with no slop, it just runs out of room before WOT on the carb. I need about an extra 3/4 to an inch of throw to get the secondaries all of the way open. Thanks for your help, hopefully some of you carb Gurus have some ideas!!
I have a holley with mech secondaries on my 454 and am having trouble getting them to open all of the way. I don't have enough throw on my accel. linkage to get all four barrels 100% open. Does anyone know if there is a different ratio secondaries linkage that would allow them to open with a shorter cable throw. Anyone run into this or have any guesses. My accelerator pedal is in good shape with no slop, it just runs out of room before WOT on the carb. I need about an extra 3/4 to an inch of throw to get the secondaries all of the way open. Thanks for your help, hopefully some of you carb Gurus have some ideas!!
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
Hey Guys,
I have a holley with mech secondaries on my 454 and am having trouble getting them to open all of the way. I don't have enough throw on my accel. linkage to get all four barrels 100% open. Does anyone know if there is a different ratio secondaries linkage that would allow them to open with a shorter cable throw. Anyone run into this or have any guesses. My accelerator pedal is in good shape with no slop, it just runs out of room before WOT on the carb. I need about an extra 3/4 to an inch of throw to get the secondaries all of the way open. Thanks for your help, hopefully some of you carb Gurus have some ideas!!
I have a holley with mech secondaries on my 454 and am having trouble getting them to open all of the way. I don't have enough throw on my accel. linkage to get all four barrels 100% open. Does anyone know if there is a different ratio secondaries linkage that would allow them to open with a shorter cable throw. Anyone run into this or have any guesses. My accelerator pedal is in good shape with no slop, it just runs out of room before WOT on the carb. I need about an extra 3/4 to an inch of throw to get the secondaries all of the way open. Thanks for your help, hopefully some of you carb Gurus have some ideas!!
Thread Starter
Instructor
Joined: Sep 2008
Posts: 200
Likes: 6
From: Palmer, Alaska
Yea, I'll have to look at that, the linkage is attached pretty high on the carb. The linkage isn't progressive, the secondaries only start to open when the primaries are at 100%
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
if the primaries are FULLY open, then the secondaries should be too....think about it ...if the front is fully open, then the throttle lever is against the stop...holley does make different linkage hook ups for the dp"s but check for full primary opening first, against the stop on the throttle bore housing...good luck
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
what throttle cable are you using?
maybe your cable is too long.
i know when i got my 72 454, it had a square bore manifold and holley on it but was still using the stock cable, the stock cable wasnt allowing the throttle lever to go back all the way.
maybe your cable is too long.
i know when i got my 72 454, it had a square bore manifold and holley on it but was still using the stock cable, the stock cable wasnt allowing the throttle lever to go back all the way.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
If the primaries are fully open, you're not going any further. Are you sure it's a mechanical secondary carb? Sounds like a vaccum secondary carb.
Thread Starter
Instructor
Joined: Sep 2008
Posts: 200
Likes: 6
From: Palmer, Alaska
I'll try and describe it as well as I can, but I'm away from the car so I can't post pics. The primary throttle blades go to fully open and has a spring loaded stop that lets the linkage continue to rotate and open the secondaries. There is a stepped cam that lets the secondaries open at a quicker rate than the primaries, ie. shorter throw, but they do not start to open untill the primaries are 90% open, then the secondaries start to crack. With the propper amount of throttle cable pull all four barrels will go 100% open, my problem is that I can't get my cable to pull far enough to open the secondaries all of the way. Sorry It would be more helpful if I had pics, but my description will have to do, and yes.... it is a Mech. secondary carb, fur sure fur sure
Last edited by Jeremy58Jeremy; Oct 1, 2009 at 01:28 PM. Reason: added more info
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Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
I'll try and describe it as well as I can, but I'm away from the car so I can't post pics. The primary throttle blades go to fully open and has a spring loaded stop that lets the linkage continue to rotate and open the secondaries. There is a stepped cam that lets the secondaries open at a quicker rate than the primaries, ie. shorter throw, but they do not start to open untill the primaries are 90% open, then the secondaries start to crack. With the propper amount of throttle cable pull all four barrels will go 100% open, my problem is that I can't get my cable to pull far enough to open the secondaries all of the way. Sorry It would be more helpful if I had pics, but my description will have to do, and yes.... it is a Mech. secondary carb, fur sure fur sure
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
I just checked this on my 650 dp sitting on the shelf that works properly.
The secondaries start to open when the primaries are ~1/2 open. Yes, the secondaries are "stepped" and open at a faster rate than the primaries such that both the primaries and secondaries reach full open at the same time.
The secondaries start to open when the primaries are ~1/2 open. Yes, the secondaries are "stepped" and open at a faster rate than the primaries such that both the primaries and secondaries reach full open at the same time.
Thread Starter
Instructor
Joined: Sep 2008
Posts: 200
Likes: 6
From: Palmer, Alaska
I'll have to take a look a mine and figure out what is going on, because my secondaries definately do not start opening that early. Mabey I have some bent up linkage parts or somthing, although everything looks like its in good shape. That why I was asking about different ratio cams, It just didn't seem right that they were opening up that late. I'll monkey with everything when I get back into town and see if I can make any progress, thanks for all of the replies, I have a couple of ideas on what I need to do now.
Melting Slicks
Joined: Jul 2006
Posts: 2,288
Likes: 489
From: Salmon Arm, BC
you can adjust the secondary opening point by bending the short link. I adjusted mine that way on a 600 DP.....a few years ago now so its not front and centre in the memory bank.....otherwise I'd be more specific.
Thread Starter
Instructor
Joined: Sep 2008
Posts: 200
Likes: 6
From: Palmer, Alaska
This is along the lines of what I was looking for. I figured I could modify that part of the linkage, but am trying to work out in my had just how to do it. Thanks for the tip!!
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
I was looking for how this is adjusted, but am not seeing it in the manual.
