For those running dual 600 sized Holleys on hot street 427's

[427LX]

Concerning the vacuum secondary setup...do you guys like the long yellow or short yellow spring and have you run with and without the check ball?
Setting up my carbs with the long yellow and modified the check ball spring seat with the "Phillips Screwdriver" peening tool to allow a bit more  vacuum flow.
Car weight is 3000 lbs. with manual trans and 3.50 gear.

[plovett]

Not sure about the spring and check ball.  I'd say just try both.  Though your car is pretty light so maybe you can start with the quicker opening.

What I wanted to ask is, do you have the diaphragms connected to each other?

paulie

[My427stang]

Typically, I don't modify vac secondaries much on any application, even dual quads

Remember they are opened by airflow through the primaries, so the harder it sucks, the quicker they open.  In fact, in most cases, I run the plain spring.

That being said, I wouldn't do as much as you are doing all at once.  The long yellow combined with making the check ball seat leak, may make them work nice on a dyno, but I would expect they'll open too quick in normal operation.  If the seats are already hit, I wouldn't go looser than purple, then try your changes.

As Paulie said, linking the covers makes them a bit more predictable too.

[427LX]

Covers are linked. Some years ago while running a hot 351W setup in same car,I made an elaborate test setup of very low tension contacts that would make ground and turn on a series of indicator lights showing how much the secondaries would open on the road. The lights would come on in sequence as the secondaries opened. Worked very well in showing real road test conditions.
Later went to a double pump mechanical carb which proved to be the quickest with the 3.89 gear and 5 spd.
Was just curious on what some of you may be running on the 427 FE engines.

Just for engineering fun I once made the worlds first adjustable air door for a Holley carb very similar to the Carter AVS.
You could swap in on any mechanical secondary Holley carb of 4150 design. Worked fairly well and only a tenth or so off what the mechanical DP Holley would run!

[thatdarncat]

Many years ago when I first started drag racing I used to test various things more. One thing I did was similar to you - I rigged a micro switch with lever to my vacuum secondaries and to a light in the dash ( just one light, not as ambitious as you lol ) Keep in mind I was mostly concerned with wide open throttle launch and not street driving, although the car did see some limited street use. What I saw for my car at the time, a 3500 lb 12.00 et Torino with 427 and Tunnel Wedge was that which spring I used didn't make much difference - they all opened fully right away, at least to the best I could measure with my light. I also didn't see any issues with bogging, etc. I don't think I bothered to check the heavy springs. My take away at the time is for my combination was it really didn't matter and I think it's just one of those things a person may have to try on their combination. After that test I generally just set my carbs and the carbs I've built for people up with the stock spring.

As far as the check ball, I have tried leaving that out on carbs a couple times to test ( different vehicles than my Torino ) and it didn't work well at all. The secondaries seem to flop rather uncontrollably. I always run the ball. I have used the Phillips screwdriver in the ball seat trick on some carbs, never had an issue with that, but I can't say if it makes much difference. I have seen some vacuum housings that the check ball fits extremely tight in the passage to the point of not moving smoothly, probably just casting tolerance, and I have a ream I use to smooth the passage. I have seen Holley vacuum secondary carbs that instead of having a check ball in the passage use a brass restriction - basically a brass plug in the passage with a small diameter hole drilled in it. A person could certainly try something like that but I think it would be a lot of trial & error.

[plovett]

I made an elaborate test setup of very low tension contacts that would make ground and turn on a series of indicator lights showing how much the secondaries would open on the road. The lights would come on in sequence as the secondaries opened.

That's really cool!   

[FordEver]

Usually either yellow, no balls. 750 QF from Barry had no balls and medium spring.
On my old vs 600,s #1850, one thing that helped wake up the 600,s was changing to  1 11 /16 base throttle plates from 750 vs. You must clearance the main body so the plates do not stick, i used a valve grinding stone. A 650 DP comes this way, just copied  the mod to the plate.
Make sure the small feed passage from the venturies  is cleaned with carb cleaner  and blown out so you get a good signal from the venturies.
Hope this helps, Bob

[427LX]

Usually either yellow, no balls. 750 QF from Barry had no balls and medium spring.
On my old vs 600,s #1850, one thing that helped wake up the 600,s was changing to  1 11 /16 base throttle plates from 750 vs. You must clearance the main body so the plates do not stick, i used a valve grinding stone. A 650 DP comes this way, just copied  the mod to the plate.
Make sure the small feed passage from the venturies  is cleaned with carb cleaner  and blown out so you get a good signal from the venturies.
Hope this helps, Bob

Glad you mentioned swapping the 650 base plates as I have been thinking on that and may try that later on.
Hopefully if we get another 50-60 degree day I will fire up my new dual quad setup....freezing or below most next week!

[e philpott]

I run the yellow spring on my Holley 600's with check ball , they open up too .... can't remember if they are long or short though

[Falcon67]

From bracket racing with a vacuum secondary, I prefer the purple spring as a starting place.  The car was more consistent with that than the softer yellow.  I've read a few studies that have seen "flutter" in VC carbs with very light springs.  If you're not concerned about consistency like I am, then it's probably not a big deal.  I'm setting up a pair of 1850s for running on a 351C and initial secondary tune will be two purples, check balls and canisters tied together.  I'm also converting the rear plates to use Holley/QF air bleeds for adjustable jetting.

I don't see how a 650 plate is going to help a 600 much - on the DP side (have not looked at the VS parts) a 4776 600 has a larger venturi diameter than a 4777 650 DP.  At least that's what their documentation shows.

[427LX]

While on this subject,I found a great way to test a VS carb for operation after a rebuild...
I take my shop vac and place the hose opening right under the  primary bore with vacuum secondary feed hole.. Slowly open the throttle to wide open while shop vac is running. You should see the secondaries open up. Works great!

[Falcon67]

I suddenly had a vision - a tunnel ram test stand powered by dual Craftsman 5 HP shop vacs.    I hereby copyright the name "VacTron".    

Good Idea, think I'll try that very thing with the shop vac.

[FordEver]

Great idea with the vacume for testing. Heres something i do to my VS carbs.
Most  VS Holleys use a diaphram with a 2.054 "  long rod, number 135-4.
I use a diaphram with a 1.97 " long rod, number 135-3 , was available on some carbs and readily available. Seems to help pull the sec open more.
I get a lot off  Holley parts from Allstate carb on line.
http://www.allcarbs.com/

[427LX]

Great idea with the vacume for testing. Heres something i do to my VS carbs.
Most  VS Holleys use a diaphram with a 2.054 "  long rod, number 135-4.
I use a diaphram with a 1.97 " long rod, number 135-3 , was available on some carbs and readily available. Seems to help pull the sec open more.
I get a lot off  Holley parts from Allstate carb on line.
http://www.allcarbs.com/

Now that is something to try. Thanks for that tip!