vac. secondary holley carbs???

is there any way to see if the secondaries are opening while the car isnt moving......someone told me that they dont open unless its under load? its a 4150 750cfm

Remove the E-Clip that holds the rod coming from the vacuum canister to the throttle plate and take the rod off the plate. Go take it out for a run and see if it runs any differently.
[addsig]

You can also try putting a paper clip on the diaphram rod near the diaphram housing.The idea is that if the rod pulls up inside the housing as the butterflies open it will push the paper clip down the rod.
[addsig]

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On 2006-03-18 12:21, frdnut wrote:
You can also try putting a paper clip on the diaphram rod near the diaphram housing.The idea is that if the rod pulls up inside the housing as the butterflies open it will push the paper clip down the rod.

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Very nice tip.[img]/forums/images/smiles/icon_wink.gif[/img][img]/forums/images/smiles/icon_tup.gif[/img]
[addsig]

I'm curious...why do you need/want to do this?

If you just want to see or hear the secondaries open, while the car is NOT moving, you can use a screw in the slot for the secondary linkage. It will make it a positive link.

If you just want to hear them them open, take the air cleaner off temporarily, while in first or second...floor it anywhere after 2000 rpm, if you can hear it...then either your headers are open, you are running them loud flowmasters or you need a serious tune up [img]/forums/images/smiles/icon_wink.gif[/img]

but...in answer to your original request, locking or blocking the slot on the secondary butterfly will force the secondaries to open when the throttle is floored. It defeats the whole purpose of have a Vacuum secondary carberator...but it works.

i had a vs carb i dont think mine ever open.
[addsig]

it can be hard to tell if they're opening on the street; even at the track. i had mine disconnected at the track, &amp; didnt feel any slowing at the fast end. then hooked it up. felt them open just before the shift &amp; picked up 3 mph. that was the stock spring. got the spring tuning kit &amp; started putting the next lighter springs in it until i couldnt feel the secondaries open. kept going lighter until i felt them open too soon. then went back to the next heavier spring. you shouldnt feel them open when properly set. if it bogs slightly &amp; takes off, its too soon. if it suddenly pulls harder, its too late.
[addsig]

what colour spring are you running now..........what CID..........what gear?
[addsig]

typically the vs carbs are 4160 series carbs and the double pumpers are 4150s.
[addsig]

If the carb is off the car, then the vacuum secondaries can be tested on the bench by running a stream of air into the passenger side primary venturi at about the eleven o'clock position looking at the carb from the front. The primary throttle blades have to be in the wide open position to do this. The pickup hole for the vacuum secondaries is at the aforementioned location and by creating a negative pressure by streaming air across that particular hole with the primary throttle blades in the wide open position, the vacuum secondaries will open if everything is like it should be. If they don't open, then start looking for a vacuum leak at where the diaphram housing either attaches to the carb or the cover goes on the housing. And the diaphram itself could also be bad.
[addsig]