1955 Tbird stock 292, auto trans.  I usually adjust the idle to 500-600 RPM with the car in Drive.

I followed these instructions http://www.eatonbalancing.com/blog/2013/03/02/modifying-the-holley-teapot-four-barrel-carb-for-late-model-distributors/

"Once the carb is reinstalled on the engine, simply hook a hose at the new port on the carb and connect the other end of the hose to the vacuum advance chamber at the distributor.  With a timing light hooked up and with the engine running and idling, there should be no timing change with the hose either hooked or unhooked. 
When I connect the hose at idle, there is a vacuum signal at idle and the timing is increasing about 15 degrees.

I could NOT get the idle set to have no vacuum at idle from the new vacuum port on the carb.   The transition hole/slot (that provides vacuum to the distributor) is exposed as I raise the idle enough to keep the car running.   I removed the carb to double check everything.  Looking at the carb from the base, I could see the slightest increase to idle RPM starts exposing the transition slot, introducing vacuum to the distributor at idle, increasing timing 15 degrees additional.........about 25 BTDC

I tried adjusting the idle with a vacuum gauge in the carb's new vacuum port, at "0" vacuum the car would stall.  Has anyone ever drilled a hole in the butterfly to get the carb to idle and keep the transition slot at "0" vacuum or is there another solution?

When I connect the hose at idle, there is a vacuum signal at idle and the timing is increasing about 15 degrees.

You have a vacuum signal @ idle (curb idle 650 RPM w/ AT in gear)? If so, you are getting a manifold vacuum signal. You made the H-4000 CARB modification, correct?

One reason you remove the vacuum signal completely while setting timing. If set with the signal removed, what is curb RPM with the signal attached?

The TRANS TV linkage has to be disconnected so that it cannot interfere with the carb curb idle setting. Make sure all linkage(s)/bushings are good.

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With the distributor vacuum unhooked, what is the initial ignition timing and at what rpm?  The presence of vacuum at the ported vacuum port of the carburetor at idle is indicative of the primary throttle blades being open too much.  Several things can contribute to this including the throttle blades in the carburetor not being properly aligned, leaking spark advance valve, idle fuel mixture too lean, the valve lash set on the tight side, the ignition timing incorrect, poor piston ring seal, leaky valves, worn valve guides, breaker points gap, flat lobe on the camshaft, worn timing chain, etc.

Drilling holes in the primary blades is usually done as a last resort.  Sometimes just cracking open the secondary side throttle blades is just enough to allow the primary blades to close enough to shut of the ported vacuum signal at idle.

As a general rule, I do not remove the throttle blades on the model 2140 and 4000 Holley 4V carbs when rebuilding.  When necessary to remove those blades, then when reinstalling them, the carburetors are held up to a light to ensure that all four blades do completely seal to the bores when seated shut.  It’s important that the blades be reinstalled with the correct side facing down as there is an angled chamfer on the blade edges to ensure a perfect seal.  Even if rebuilding the carbs and not removing the blades from the shafts, it’s still a good ideal to check that the blades do seal completely when closed as even a backfire can distort the blades.

Lorena, Texas (South of Waco)

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The timing at idle in park @ 800 RPM (This goes down to about 500/550 RPM in Drive), 10 BTDC (this is with the vacuum port on the carb plugged).   The car is running fine, there could be internal engine wear,  I don't have documentation for whatever has been previously done.  I believe there was a rebuild in the recent past.........  Whatever is going on I am not ready to rebuild the engine.

I didn't touch the throttle blades on this carb. I have a plug with a gasket and thread sealer for the spark advance valve.

I had the carb off yesterday.   I loosened the idle adjustment screw and the vacuum port hole was covered.  The slightest adjustment seemed to expose the vacuum port, which is why I was considering drilling a hole in the throttle blades.

When you say: " Sometimes just cracking open the secondary side throttle blades is just enough to allow the primary blades to close enough to shut of the ported vacuum signal at idle."   How would I do this?   Is there an adjustment for the secondary shaft/blades?

Manifold vacuum is steady at 20.

HERE - https://www.mustangtek.com/Library5/PDF/Holley4000.pdf

It should have all of the CARB SPECS. If not will be found in the FORD/BIRD WORKSHOP MANUAL.

Check all linkage(s) and adjustments. Remove throttle linkage(s) while adjusting or adjust on bench.

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Whereas the model 4150 & 4160 Holley four-barrel carbs do have an adjustment for the secondary throttle blades, the model 2140 & 4000 Holley 4V carbs do not.  With that in mind, then adding a pair of holes in the throttle blades is an option.  Before doing that though, hold the carburetor up to a light source with both the primary and secondary throttle blades completely closed and ensure that no light is seeping past the blades.  If there’s light, then you have some extra air getting past the blade or blades that will need to be corrected before going any further.

While it’s customary to add the extra ‘air’ holes in the primary blades, I do not see an issue with putting them in the secondary blades.  I personally would start with 1/16” holes as you are not going to need much and give that a try first.  Easy enough to drill the holes larger but much tougher to make them smaller.

Lorena, Texas (South of Waco)

Thank you for the replies.   I am going to try to tune it the way it is before I drill anything.   It's been raining here 4/5 days a week for the past couple of weeks.

When it stalls, maybe it is going lean.
  Are all the idle transfer slots/ports clear? (2 or 3, depending on gen, in each primary port)
  Check the air bleeds on the top cover and ensure they are not blocked. Some carbs have a very large washer there and may be closing them off. There should be a small gap.
  Check the accelerator pump rod has vent holes, they should both be open in warm weather.


1936 Ford 3W Coupe : 56 T-Bird 312, 47 Packard 3 speed, 40 juice brakes.
1968 Merc Cyclone FB GT 390, Getting a better front clip!
1977 Ford F-250 Supercab RWD Explorer Long box.
1976 Chev Camaro RS LT
Future rebuild : 1949 Ford F-1