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Old 07-09-2007, 09:40 PM   #1
bob-n
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Default Holley 94's... can I add vacuum port??

I've got a pair of Holley 94's on my Dodge flathead 6. Both carbs are casting number 8BA, but neither have the vacuum port for the vacuum advance. I'm wondering if anybody has taken a shot at adding this port? Is it possible or am I going to f-up a pair of good running carbs?
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Old 07-09-2007, 09:59 PM   #2
47bob
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Default Re: Holley 94's... can I add vacuum port??

Bob, You will need manifold vacuum for that motor;leave the carbs as they are. That 8BA vacuum will give timeing the wrong signel anyway. .....Bob
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Old 07-09-2007, 10:03 PM   #3
dickster27
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Default Re: Holley 94's... can I add vacuum port??

Bob, just go to an intake port under the carb and drill and tap a 1/8" pipe thread and screw a nipple in for your vacuum. That's without a doubt the easiest way to get were you want to be. Or, jump on the Bay and win a vacuum plate that mounts beneath the carb. Your call.
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Old 07-09-2007, 10:11 PM   #4
bob-n
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Default Re: Holley 94's... can I add vacuum port??

I had the advance set up on the manifold, but it didn't "feel" right. Tried running without any vac advance and it ran like shit (like a stock 1 barrel)

I'll put it back to the manifold then and stop thinking so much.

Thanks... Bob
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Old 07-09-2007, 11:30 PM   #5
Eric Von Zipper
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Default Re: Holley 94's... can I add vacuum port??

Bob,

Not the carbs the manifold

look inside and make sure you drill thru the chamber between the carbs into the common area.

I did this under the middle carb on my 3 pot and between the two pots on both of my Fentons
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Old 07-10-2007, 12:37 AM   #6
Mr 42
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Default Re: Holley 94's... can I add vacuum port??

The problem here is when the engine is idling, there should be no vacum to the distributor. Thats the reason for using ported vacum. So you only have the initial vacuum when idling and as soon you open the throttle you will get additonal advance vacuum.

Henry Fordd tried to save money and made a special distributor advance system. Using the difference between vacum above and under the throttle plate's. And when connecting a Standard 8BA distributor to manifold vacuum it will work backward´s! And when adding more carbs it will need tuning to get it to work right again.

Check out this article ita a bit old but its still valid.
http://www.btc-bci.com/~billben/navarro.htm
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Old 07-10-2007, 12:58 PM   #7
Bruce Lancaster
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Default Re: Holley 94's... can I add vacuum port??

This is an engine with "normal" centrifugal/vac advance, probably an Autolite, not the dreaded Holley Loadamatic...
He didn't like the results with manifold vac, and wants to try ported vac, as I read it...
With the 8BA carbs, this is simple: You presumably have a plug or a pinched-off original vac line in the '49 Ford advance hole in the rear of the central main body. Remove that...scrutinize the inside area. You have a small hole going straight ahead to the venturi--pluggit any way you like. The second hole, heading down into the throttle body casting, is ported vac. Make sure uou have the proper gasket with a hole for this between main body and throttle casting and try your car with advance hooked up to the '49 Ford setup, venturi vac disabled. This is exactly how Mallory did the job with its aftermarket '49 Ford distributors.
I believe the passage in carb body may be very small...don't know if this will affect response. You probably own a drill, if it does...
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Old 03-05-2013, 06:09 PM   #8
grovedawg
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Default Re: Holley 94's... can I add vacuum port??

I don't know how this link hasn't made it onto this thread, but it's a great little write up on how you can convert 94's and 2100's to a ported vacuum that will work on new distributors with vacuum advance:

http://www.eatonbalancing.com/blog/2...-distributors/
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Old 03-05-2013, 09:25 PM   #9
Retrorod
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Default Re: Holley 94's... can I add vacuum port??

Good info.
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Old 03-06-2013, 09:55 AM   #10
Bruce Lancaster
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Default Re: Holley 94's... can I add vacuum port??

That way is useful only with the very late carbs that have the extra valve; the common 1949-53 types have ported vac to the rear port for the Loadamatic and need only to have the extra hole for venturi vac plugged, as noted above.
Look into the hole in the back of the carb...a small hole goes in straight to the venturi. Pluggit. FWIW, early Mallory distributors came with a little plug for just this purpose...
The remaining downward hole is the ported vac. All you need to to is check on the gasket between throttle and main bodies and make sure you have the right one with a hole for this vac passage.
If you are using a '37-48 type carb with no vertical vac passage, you can go in right through the base as Ford did on some of the Lincoln V-12 carbs. The Lincolns had a small cast boss for this but you don't really need that.
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Old 03-06-2013, 10:06 AM   #11
Dreddybear
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Default Re: Holley 94's... can I add vacuum port??

I went to add this thread to the Holley page, but it's already there! I did however add the link to eaton balancing. Thanks grovedawg.
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Old 11-01-2013, 02:08 AM   #12
hb32
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Default Re: Holley 94's... can I add vacuum port??

Quote:
Originally Posted by Bruce Lancaster View Post
Look into the hole in the back of the carb...a small hole goes in straight to the venturi. Pluggit. FWIW, early Mallory distributors came with a little plug for just this purpose...
The remaining downward hole is the ported vac. .
Any pics of this plug or do you know where to get the instructions?
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