Vaccum secondaries

• Aug 29, 2021

• #1

mountain33

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I have a Holly 4160 carb. On a stock 383 71 RR. My problem is while running the car without engaging the secondaries all is great. Once the four barrel opens up. They wont close. The first time luckily i was on a long straight road and keep hitting gas and releasing and they closed. The second time it happened not so lucky. I managed to pull into a parking lot and kill ignition. Once doing that everything is fine. What returns the secondary back to close position? Is it a spring or is it the drop in vacuum that closees them? I had rebuilt the carb when i got the car 2 years ago. Im careful not to open the four barrel but its something i should fix. Thanks for any thoughts.

 

• Aug 29, 2021

• #2

Fran Blacker

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Throttle plates catching on manifold or the gasket. Check the carb with it off. On my crossram tried a thin gasket throttle suck, checked before starting. Crossram carb gaskets are 3/4 times thicker than the thin ones.

Edit: When test carb, open primaries then secondarily by hand. They should open smoothly .

 

Last edited: Aug 29, 2021

• Aug 29, 2021

• #3

Photon440

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There should be mechanical linkage as well as the vacuum. The linkage runs through a slot that forces the secondary to close when the primary closes but doesn't open the secondary when the primary opens.

 

• Aug 29, 2021

• #4

oldbee

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Or maybe a loose throttle plate that is shifting around?

 

• Aug 29, 2021

• #5

Y

yella71

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Nothing like having your throttle stick wide open......nothing

 

• Aug 29, 2021

• #6

dadsbee

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Turn the key to off, or grab the next gear.. . LOL

 

• Aug 29, 2021

• #7

mountain33

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Photon440 said:

There should be mechanical linkage as well as the vacuum. The linkage runs through a slot that forces the secondary to close when the primary closes but doesn't open the secondary when the primary opens.
View attachment 1160023

Click to expand...

Thanks for the response so quickly. Going out to check the manual linkage. I might of screwed something up there.

 

• Aug 29, 2021

• #8

RJRENTON

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Photon440 said:

There should be mechanical linkage as well as the vacuum. The linkage runs through a slot that forces the secondary to close when the primary closes but doesn't open the secondary when the primary opens.
View attachment 1160023

Click to expand...

YES....TOTALLY AGREE....the secondary butterfly valves are opened by vacuum but MECHANICALLY closed by the link shown AND with an assist from the spring in the opening diaphragm housing (or pod). If the base gasket was infringing on the secondary throttle bores, the closing and opening would also be affected. It sounds like the rebuilder omitted the "force the secondary close safety link" shown in the pix. Just my opinion of course.
BOB RENTON

 

• Aug 29, 2021

• #9

mountain33

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I agree with the whole experience of having the throttle stick. I keep thinking how good are these stock drum brakes? Car kept going faster and faster. I was glad the Mrs wasn't with me.

 

• Aug 29, 2021

• #10

oldbee

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Bob just made me think of another. Check the sec.linkage for rubbing on the outside of manifold also.

 

• Aug 29, 2021

• #11

mountain33

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Fixed. I cleaned up the linkage and put some Teflon lube on it. I could feel a difference right away. Kept working it took it out for a ride opened it up multiple times worked great. I probably should of stomped on it more but never needed to. The more i opened up the secondaries the better it got. thanks to all. I was getting ready to order a new carb. now i can spend that money on something else. thanks again

 

• Aug 31, 2021

• #12

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383man

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Glad you got it fixed. I was going to say they also use a check ball in the carb so the secondaries will close fast enough and if that check ball is stuck they will still open normal but if the check ball does not lift off its seat when the throttle is released the vacuum does not get out fast enough and can also hold the secondaries from closing fast enough. Ron