Holley Spring question
Thread Starter
Burning Brakes
Joined: Aug 2007
Posts: 814
Likes: 7
From: toronto ontario
Holley Spring question
I have a 600 vacuum Holley (not original). The only adjustment that it has is for the float bowls. I would like the secondaries to open sooner.
Took the spring out and found that it is natural steel color. I thought that it should be replaced with a softer spring. A friend said that for the secondaries to open sooner it will need a stronger spring. Does not sound right to me.
Which is it??? If it is the stronger spring can you tell me how that works.
Took the spring out and found that it is natural steel color. I thought that it should be replaced with a softer spring. A friend said that for the secondaries to open sooner it will need a stronger spring. Does not sound right to me.
Which is it??? If it is the stronger spring can you tell me how that works.
Le Mans Master
Joined: Nov 2015
Posts: 7,472
Likes: 2,647
From: Really Central IL Illinois
www.holley.com I think???
I have a Holley tuning manual from the 70s, but have visited their web site and found more recent information is available there.
I am thinking you need a lighter spring to open the secondaries sooner as that is the function of the vacuum secondary diaphragm. Don't go by this, look it up on their site - they built it.
I have a Holley tuning manual from the 70s, but have visited their web site and found more recent information is available there.
I am thinking you need a lighter spring to open the secondaries sooner as that is the function of the vacuum secondary diaphragm. Don't go by this, look it up on their site - they built it.
Instructor
Joined: Apr 2015
Posts: 219
Likes: 61
From: Monrovia IN
My 600 Holley felt & sounded like a 2 barrel out of the box. They are shipped with the heavy spring, probably for fuel economy. I bought the spring kit, put in the second lightest spring, and it really feels & sounds like a 4 barrel now!
Safety Car
Joined: May 2014
Posts: 3,785
Likes: 656
Put a paper clip on the secondary diaphragm rod and slide it up top then go for a ride, the clip will tell you how the secondaries are working.
You should not feel secondary operation on a vacuum secondary carburetor. There may or may not be a check ball in the diaphragm housing to delay the vacuum signal but it may be best to just experiment with a lighter spring.
Do some research on how the vacuum secondary works, it's a very good design for a street carburetor. There is a small hole in the primary venturi that picks up a VENTURI vacuum signal when primary air flow is high enough. That signal is bleed off by a connecting hole in the secondary venturi until the signal becomes strong enough to lift the secondary diaphragm. As the air starts to move through the secondary venturi the bleed hole changes from bleed to vacuum and adds to the signal from the primary venturi hole further opening the secondary.
You should not feel secondary operation on a vacuum secondary carburetor. There may or may not be a check ball in the diaphragm housing to delay the vacuum signal but it may be best to just experiment with a lighter spring.
Do some research on how the vacuum secondary works, it's a very good design for a street carburetor. There is a small hole in the primary venturi that picks up a VENTURI vacuum signal when primary air flow is high enough. That signal is bleed off by a connecting hole in the secondary venturi until the signal becomes strong enough to lift the secondary diaphragm. As the air starts to move through the secondary venturi the bleed hole changes from bleed to vacuum and adds to the signal from the primary venturi hole further opening the secondary.
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
A lower tension secondary diaphragm spring will open the secondaty throttle sooner. tbarbb is spot on about feeling secondary operation. Feeling secondary operation usually shows up as a "kick in the pants" acceleration a short time after mashing the throttle. This condition is usually referred to as "bogging." Use the lightest spring that does not result in bogging.
If you don't want to experiment with springs (unless you have a quick spring change cover on your secondary diaphragm housing, another solution is to replace the Holly diaphragm with a Quick Fuel adjustable secondary actuator. They are a direct bolt on for 4150/4160 series Holley carbs. Here's one on my Holley 3310:
http://s656.photobucket.com/user/abe...lpryd.jpg.html
If you don't want to experiment with springs (unless you have a quick spring change cover on your secondary diaphragm housing, another solution is to replace the Holly diaphragm with a Quick Fuel adjustable secondary actuator. They are a direct bolt on for 4150/4160 series Holley carbs. Here's one on my Holley 3310:
http://s656.photobucket.com/user/abe...lpryd.jpg.html
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
A lower tension secondary diaphragm spring will open the secondaty throttle sooner. tbarbb is spot on about feeling secondary operation. Feeling secondary operation usually shows up as a "kick in the pants" acceleration a short time after mashing the throttle. This condition is usually referred to as "bogging." Use the lightest spring that does not result in bogging.
If you don't want to experiment with springs (unless you have a quick spring change cover on your secondary diaphragm housing, another solution is to replace the Holly diaphragm with a Quick Fuel adjustable secondary actuator. They are a direct bolt on for 4150/4160 series Holley carbs. Here's one on my Holley 3310:
If you don't want to experiment with springs (unless you have a quick spring change cover on your secondary diaphragm housing, another solution is to replace the Holly diaphragm with a Quick Fuel adjustable secondary actuator. They are a direct bolt on for 4150/4160 series Holley carbs. Here's one on my Holley 3310:
Thread Starter
Burning Brakes
Joined: Aug 2007
Posts: 814
Likes: 7
From: toronto ontario
spring
went with a lighter spring, carb had a natural color spring. Used the yellow spring from the Holley kit. Performance is much better, no Bogg. Got a Holley spring kit with instructions so I can play with it a bit. Thanks for the info guys
