Carburetor Question

well it could be that your car isn't making much vacuum or it could be that your diaphram in the vacuum canister or whatever it is called on the carb is ripped or leaking. the other option is the spring that the vacuum has to over come in the vacuum canister on the carb is to strong.

It would be best if you posted the Holley list number of the carb. What I am saying here is based on my 80457 carbs. These are 600 cfm universals with a Ford kickdown linkage for a C4 or C6.

The vacuum secondary opens when vacuum is applied to the vac cannister. The vacuum is venturi vacuum from the primary bores, not manifold vacuum. The passage comes out the side of the main body through a small hole that lines up with a boss and a passage in the vac secondary unit. Take the vac unit off and make sure the little cork gasket is there. New ones have sticky on them.

The last one I had trouble with ended up with the actual vacuum diaphram having a leak because I pinched it putting the cover on a couple years ago.....

When you have the vacuum unit off, test the diaphram with a vac pump or other means to see that it does not leak. If it leaks, take the cover off and see if the vacuum diaphram has leaks, or if it was not clamped between the base and cover.

Sorry for the long reply, but that's the best I can explain it.

Otherwise, make sure the diaphram, shaft and linkage move freely, etc.

The vacuum secs will only open under load at higher rpms. I got the spring kit from holley and it lists the earliest open points for secondaries as something like 2500 rpms on a 302. They will not open in neutral revving the engine.

You need to do the string trick. Tie some floss around the advancing side of the secondary lever and then loop the other end around something nearby so there is no pulling resistence but the string holds itself up. Then go for a very spirited drive and get it over 3500 rpms under load and see if the string is now slack.If not, you have stuff to fix.

Go from there.

GOtta be the right temp/ the right rpm's the right time to open em up...Try 2100 rpms then bash on it. get the car warmed up first.

Mechanical Secondaries > Vaccum Secondaries.

I never have to worry about when mine are open, i just press the loud button and off i go