Vacuum Secondaries not working
Thread Starter
Instructor
Joined: Jun 2006
Posts: 196
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Vacuum Secondaries not working
Any of you have any idea why my vacuum secondaries don,t work ?
I have been told that I have a vacuum leak somewhere in the Holley Carb.I have read all of the Threads on how tempermental Holleys are and may just buy a new one.
64 muscl
I have been told that I have a vacuum leak somewhere in the Holley Carb.I have read all of the Threads on how tempermental Holleys are and may just buy a new one.
64 muscl
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Originally Posted by 64muscl
Any of you have any idea why my vacuum secondaries don,t work ?
I have been told that I have a vacuum leak somewhere in the Holley Carb.I have read all of the Threads on how tempermental Holleys are and may just buy a new one.
64 muscl
I have been told that I have a vacuum leak somewhere in the Holley Carb.I have read all of the Threads on how tempermental Holleys are and may just buy a new one.
64 muscl
The secondaries won't usually pull open if you're sitting in the driveway jazzing the throttle. The engine has to have a load on it.
The MAIN problem with Holleys is people working on them overtorque the screws that hold them together and the nuts that hold it to the engine. That's one thing that causes warped main bodies and warped/broken bases. If you're going to buy a new Holly, send me your old one. I'll pay postage.
Last edited by MikeM; Jul 6, 2006 at 08:29 AM.
Safety Car
Joined: Apr 2001
Posts: 3,574
Likes: 0
From: Middleboro/Boston MA
If your sure they are not opening then
there may be a leak in the secondary diaphram, this is what it looks like opened up.
Taken from here... http://web.njit.edu/~gag0046/holley/rb4160/
there may be a leak in the secondary diaphram, this is what it looks like opened up.
Taken from here... http://web.njit.edu/~gag0046/holley/rb4160/
Intermediate
Joined: Feb 2005
Posts: 32
Likes: 0
From: Suffolk County NY
Can you open the secondaries manually? If so you might just need a new diaphragm. Also, there are about 5 different springs available to let them open sooner or later. You might have a really strong one in there now.
Safety Car
Joined: Feb 2003
Posts: 4,068
Likes: 27
From: St. Joseph Mo
Originally Posted by StingRayls6
Can you open the secondaries manually? If so you might just need a new diaphragm. Also, there are about 5 different springs available to let them open sooner or later. You might have a really strong one in there now.
Melting Slicks
Joined: Apr 2005
Posts: 3,113
Likes: 4
I just ordered this so that i can make quick spring changes. Once you replace your diaphram, cork gasket, etc. i recommend toping the rebuild off with one of these. Its a real pain when you are trying to get just the right spring to tune the car into your own personal preference and you have to remove the diaphram assembly 5 times. This will save you a lot of trouble!!
http://store.summitracing.com/partde...5&autoview=sku
You will also need this
http://store.summitracing.com/partde...5&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku
You will also need this
http://store.summitracing.com/partde...5&autoview=sku
Advanced
Joined: Jun 2006
Posts: 83
Likes: 0
From: Rockford MI
Not trying to hijack your thread, but another question just occurred to me: how can you tell for sure if your vacuum secondaries are opening or not? Mechanical is easy (push the throttle and watch), but what about vacuum - is it purely a "drive it and feel it" thing?
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Racer
Joined: Dec 2004
Posts: 480
Likes: 12
From: St. Louis Mo.
There is a rod that connects the primaries to the secondaries that cracks the secondaries open a little bit then the vacum takes over and opens them completley. I have had to bend that rod just a tad to get vac. secondaries to work in the past.
Instructor
Joined: Jun 2001
Posts: 231
Likes: 0
From: Cedar City UT
Secondaries
To check operation you can attach a wire wrap around the diaphram rod at the top. When the secodaries open the wrap is pushed down.
Another item that will prevent opening is a check valve in a vacuum unit that does not have a groove in the seat. The chk vlv and grooved seat alow a metered flow of vacuum so the secondries don't slam open. Some units don't have a groove in the seat and won't open if a chk vlv is installed
LOL Bob
Another item that will prevent opening is a check valve in a vacuum unit that does not have a groove in the seat. The chk vlv and grooved seat alow a metered flow of vacuum so the secondries don't slam open. Some units don't have a groove in the seat and won't open if a chk vlv is installed
LOL Bob
Thread Starter
Instructor
Joined: Jun 2006
Posts: 196
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Rebuild Info
Originally Posted by Crazyhorse
If your sure they are not opening then
there may be a leak in the secondary diaphram, this is what it looks like opened up.
Taken from here... http://web.njit.edu/~gag0046/holley/rb4160/
there may be a leak in the secondary diaphram, this is what it looks like opened up.
Taken from here... http://web.njit.edu/~gag0046/holley/rb4160/
64 muscl
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Originally Posted by rahzip
There is a rod that connects the primaries to the secondaries that cracks the secondaries open a little bit then the vacum takes over and opens them completley. I have had to bend that rod just a tad to get vac. secondaries to work in the past.
Racer
Joined: Dec 2004
Posts: 480
Likes: 12
From: St. Louis Mo.
That link rod only ensures that the secondaries are pulled closed mechanically by the primary shaft in the event the secondaries stick open or if the diaphragm fails (safety feature); has nothing to do with opening the secondaries
It was explained to me that down in your sec. bores there are is a small port that when a passes by it it causes a vacum to pull the secondaries open. With out the sec. throtle blades opening a little bit the air can not past those ports to cause the vac.
John, As you know I'm know Holley expert!! I am going on what I was show when I was have problems with one of my carbs. We pulled it off the car blew air across that port and nothing happened. Tweaked the rod tried it again, and the secodaries open completely.
Not trying to cause a debate or argue. Stick with what John said
Thank you for you help with the pm's. I'm still having problems
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Originally Posted by rahzip
Sorry if I mis-spoke
It was explained to me that down in your sec. bores there are is a small port that when a passes by it it causes a vacum to pull the secondaries open. With out the sec. throtle blades opening a little bit the air can not past those ports to cause the vac.
It was explained to me that down in your sec. bores there are is a small port that when a passes by it it causes a vacum to pull the secondaries open. With out the sec. throtle blades opening a little bit the air can not past those ports to cause the vac.
Safety Car
Joined: Feb 2006
Posts: 4,142
Likes: 704
The following is a quote from the "Super Tuning and Modifying Holley Carburetors" book by Dave Emanuel. If you have a Holley carb, you need this book.
Holley kit number 20-13 contains a number of color-coded secondary diaphragm springs. By simply changing the spring the opening rate can be optimized for any engine/chassis configuration. Heavy vehicles with small engines will require a relatively stiff spring in order to prevent the secondaries from opening too soon and causing a stumble. Lighter cars with larger engines will tolerate a much lighter spring load because RPM increases more rapidly.
Conversion to mechanical actuation is a mistake since there will be no accelerator pump circuit supplying fuel to the secondary bores. As is the case with too weak a spring, mechanical actuation can result in a severe stumble and misfire.
Holley kit number 20-13 contains a number of color-coded secondary diaphragm springs. By simply changing the spring the opening rate can be optimized for any engine/chassis configuration. Heavy vehicles with small engines will require a relatively stiff spring in order to prevent the secondaries from opening too soon and causing a stumble. Lighter cars with larger engines will tolerate a much lighter spring load because RPM increases more rapidly.
Conversion to mechanical actuation is a mistake since there will be no accelerator pump circuit supplying fuel to the secondary bores. As is the case with too weak a spring, mechanical actuation can result in a severe stumble and misfire.
Drifting
Joined: Feb 1999
Posts: 1,808
Likes: 28
From: CA central coast
This may be too simplistic, but I've seen where a carb base gasket was cut just a bit off center (or the hole is a shade too small or there's a bit too much play in the bolt holes, allowing the gasket to move out of position), and the gasket interferes slightly with the secondary butterflies and keeps them from opening.
Le Mans Master
Joined: Jan 2002
Posts: 8,913
Likes: 283
Also, the throttle blades can "Bind" if the shaft is worn, or they are set to low. There is very small hex bolt under the secondary shaft that limits how far the throttle blades seat. The specs escape me at the moment.
I use a paper clip, slid over the rod to check when they start to open. I run the car to 3500 RPM, pull over and look at the paper clip, it will slide down the rod. I do this in 500 RPM intervals.
You can't really "force the secondaries open" like a mechanical carb. There is no accelerator system for the rear. You could cheat this by installing a larger pump nozzle up front, with a larger, more aggressive pump cam. But this would hinder part throttle and off idle performance.
PS, don't cut the diaphragm springs, this makes them stronger!
And, when a vacuum secondary carb is tuned perfect, you should not hear the secondaries come in, or feel them, the motor should just scream. NO BOG, No sudden kick, or stumble then kick.
Mark
I use a paper clip, slid over the rod to check when they start to open. I run the car to 3500 RPM, pull over and look at the paper clip, it will slide down the rod. I do this in 500 RPM intervals.
You can't really "force the secondaries open" like a mechanical carb. There is no accelerator system for the rear. You could cheat this by installing a larger pump nozzle up front, with a larger, more aggressive pump cam. But this would hinder part throttle and off idle performance.
PS, don't cut the diaphragm springs, this makes them stronger!
And, when a vacuum secondary carb is tuned perfect, you should not hear the secondaries come in, or feel them, the motor should just scream. NO BOG, No sudden kick, or stumble then kick.
Mark
Burning Brakes
Joined: Dec 2005
Posts: 998
Likes: 2
Originally Posted by buns
The following is a quote from the "Super Tuning and Modifying Holley Carburetors" book by Dave Emanuel. If you have a Holley carb, you need this book.
Holley kit number 20-13 contains a number of color-coded secondary diaphragm springs. By simply changing the spring the opening rate can be optimized for any engine/chassis configuration. Heavy vehicles with small engines will require a relatively stiff spring in order to prevent the secondaries from opening too soon and causing a stumble. Lighter cars with larger engines will tolerate a much lighter spring load because RPM increases more rapidly.
Conversion to mechanical actuation is a mistake since there will be no accelerator pump circuit supplying fuel to the secondary bores. As is the case with too weak a spring, mechanical actuation can result in a severe stumble and misfire.
Holley kit number 20-13 contains a number of color-coded secondary diaphragm springs. By simply changing the spring the opening rate can be optimized for any engine/chassis configuration. Heavy vehicles with small engines will require a relatively stiff spring in order to prevent the secondaries from opening too soon and causing a stumble. Lighter cars with larger engines will tolerate a much lighter spring load because RPM increases more rapidly.
Conversion to mechanical actuation is a mistake since there will be no accelerator pump circuit supplying fuel to the secondary bores. As is the case with too weak a spring, mechanical actuation can result in a severe stumble and misfire.
Well that answers that....
Mine are operating, wait a minute, what the hell am I thinking, never mind, I'm not EVEN going to say THAT out loud.....
I could probably go with a lighter spring since I "rollered" my motor but.....(refer to above).....
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
Originally Posted by Formula Outlaw
Not to sound like a complete idiot but:
Has anyone, or is there any way, to change it to a mechanical operation????
Has anyone, or is there any way, to change it to a mechanical operation????
You can also change the secondary bowl and metering block to make a true double pumper, but that would be expensive.