OK so im running the car in my sig and as it says, i cant get the back two barrels to open up. It should be a vacuum secondary, its a holley 600 4bbl, but the vacuum never activates the secondaries. even when you move them yourself as you increase the throttle no gas flows through them. How does one cut the fuel off to the back two or more importantly how do i get it flowing again? also then how do i run the vacuum to open up the secondaries? Sorry for the long post but this is my first carbed car.
Carburetor Question
- Thread starter DouglasOhio
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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 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.
crazypete
All my crevices are greased.
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.
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.
i know they arent opening because the front two blades are clean from the gas through them, the back two are dirty with spots of rust. NO neeeed for a string, thats definitely something ill add to my collection of tricks tho. Thanks for the help, i think im just going to say tohell with it and ask (pray) for a carb for my 18th. Thanks guys.
Mechanical Secondaries > Vaccum Secondaries.
I never have to worry about when mine are open, i just press the loud button and off i go
I never have to worry about when mine are open, i just press the loud button and off i go
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