Inlarging the PVCR's from .040 to .070 allows sufficient fuel were the previous lean condition was, allowing the main jets to be properly tuned instead of causing a pig rich condition covering the lean condition caused by the to small PVCR's in the circled in the power valve mount.

The 2 holes circled to the left, the hole to the right feeds the transition slot in the throttle plate and the channel the hole sits in at the top connects to the main well. The hole to the left is for the air fuel mixture and feeds a hole in the throttle plate below the transition slot and the butterfly. The butterly needs to cover the majority of the transition slots in order for the air fuel adjusters to work, usually about .020" is uncovered.

To set the idle and to keep the transition slot mostly covered so the air fuel mixture screws work, some times the 2ndary is open slightly to increase idle, or holes are drilled in the primary butterflys to allow air to flow to increase idle allowing the air fuel mixture screws to work.

For fine tuning, sometimes the idle fuel restrictor which is to the right of the 2 holes circled is removed and relocated to the top of the channel from the right hole in the transition circuit that connects to the main well at the top, the connection to the main well is taped for adjustable idle fuel restrictors for fine tuning, which may or may not be necessary, just because it can be done doesn't mean it needs too. 

Once the primary has been sorted and the throttle operation is smooth and trouble free, then the 2ndry tuning can start

Basic Info: 66-67 Holley introduced the 3 Barrel for public consumption. In 1964 Chrysler had Holley build them a carb list #3085  for their Nascar Hemi motors and this was the Holley 3 Barrel. There has been no info as to tuning issues with the Nascar version.

Now, 66-67 with the introduction of the 3 Barrel to the public, some how emissons became involved and the carbs were tuned to meet those standards. In this case the Emisson standards seem to go towards leaning these carbs out. I don't know if Holley ever tested these carbs or if the changes were just done on paper.

For such a large carb Holley had installed .040" PVCR's in the primary metering block #5615 to lean the primary out to meet Emission Standards, resulting in a flat spot, the initial fix was to go larger jets which caused it to run pig rich, so now this is just the primary issue, now the 2ndaries were also lean and at wide open throttle there was a substantial bog from being to lean, an idea came up for a fix, which was to remove the vaccum canister and make the primary and secondary one to one, so gears were made, and a primary shooter was extended to the secondaries for a fuel shot to richen up the secondary during the lean peroid during blade opening.

Previously, everything done were just Band Aids and didn't NECESSARILY fix any of the issues.

The Nascar's 3 Barrel metering block #4328 came with .093' PVCR's and they had emulsion tubes in the main well reducing fuel flow, so the larger PVCR was needed.

Now, the newer 3 Barrels came with metering Block # 5615 and had a .040" PVCR, and does not have emulsions tubes in the main well, and the primary side of the 3 Barrel is basicly the same as the primary side of the Holley 850 Double Pumper, so tuning is about the same. The PVCR's in the metering plate of the 850 DP are .070" and also do not have emulsion tubes in the main well.

So, to tune the 66-67 and newer 3 Barrels, you open the PVCR's on the #5616 metering plates from .040" to .070" and proceede to tune the 3 Barrel primary's the same as you would an 850 DP consiting of the fuel mixer screws, the transition circuit, primary jets and power valves. There are plenty of tutorials on line for tuning an 850 DP for referencing if you have questions. I'll add more later concerning the tuning of the 2ndarys, actually half of it s getting the primaries tuned.


 

Quote from: 1967 XR7 GT on September 06, 2026, 04:15:39 AM

. . . . . . . dull, flat colorless, lacking any Iridescence, crap job.

. . . . . .  as can be seen it's just a flat green color, will try later to provide a better complete pic of the carb.

     Though the coloration of your carburetor might not be what you were hoping for, it actually isn't unlike that of what many having come out of Holley looked like, "originally".  The finish as delivered by Holley wasn't very consistent, and the individual componentry items were often different in coloring, and this only became more so as the decades progressed.   

      And with this observation,  I'm of the opinion that some of the quite bright finishes as being executed today of "refinished/restored" examples as has become expected, being required in the industry to provide the impression of a quality execution, but is not representative of mostly that as which Holley provided , back then.      

      Scott.

Here is an example of color from back then, it's my NOS Holley 4604-S 1050 CFM 3 Barrel, the color has faded some I would think since the late sixties code 973 Year 1969, month 7, in the 3 week, over 50 years.

I did some research, what I had done was called "Vapor Honing", there is also "Vapor Blasting" "Wet Blasting,"  and "Dustless Blasting" these processes are all different.

So, I need to up date my warning: Do not do Vapor Honing to your Holley Carb before  coloring. As to Vapor, Wet, and Dustless Blasting, you'll have to do your own research as to  the coloring results after, I've not used those processes so I don't know their results.

My Intake Manifold I had used Vapor Honing not Vapor Blasting, and I now remember I had Vapor Honing done to protect the Manifold, as was demostrated to me I took dirty grease and wiped a spot on the Manifold, then wiped it off with a rag, no discoloring, stain or any indication that grease had been on the manifold. If grease had been wiped on a Manifold that had been bead or sand blasted, there would be a stain where it was applied.
 

There is a whole 300 page book that I could write about this.


Why are you certain that variable was the issue?

My carb is a Holley 1030 cfm 3 barrel. The guy who did the coloring had me wait after he received my carb, he wanted to wait till he had enough carbs to do a run. I guess he didn't like to color one at a time.

He had said my carb was the only one the coloring turned out this way out of the run, and was the only one vapor blasted.

I had my intake vapor blasted before my carb, and the finish is different, including the feel and even the look which is a flat dull aluminum, which is exactly how the coloring came out

So basically it is a 488 cube, 11 to 1, pump gas, not ideal cam, 1050 carb. I will post numbers after some guesses.

After the results of 723.1 HP, 638 tq and state a bit of an over achiever., why would you then say "not ideal cam" ?

I see a combination that worked and made really good numbers. What were the heads flow numbers ?

I, have been collecting the parts needed to complete my TP Heads. I went with Manley 10 deg Titanium Retaines, 10 deg Titanium Locs, Spring Locators and .015" shims. I, went with PSI Nascar Cup Springs. They were out of stock when I called, I had to wait 6 weeks for the next run, which just showed last week. I chose to go with the ML (Max Lfe) treatment, A proprietary, multi-step surface enhancement process that has been proven to increase spring endurance.

The heads are being built to meet the requirements of a billet core solid flat tappet cam I picked up, spec's are 265/278 @ .050", 108 LSA, with a .715" gross lif. The PSI springs will be set up with around a 1.935" installed height with about 224 pds closed and an open pressure of around 534 pds at about 1.240" .090" Distance to Coil Bind, with a .695" valve lift after lash.

2pcs Molnar 7.000 connecting rods for BBC CH7000VTB-T8-A for nitrous,  Buxton Compressor

Rod Length 6.8750 :  10.150 DH  0 Deck  1.150 Piston CH Stroke 4.250
Rod Length 6.8950 - 10.170" DH  0 Deck  1.150 Piston CH Stroke 4.250
Rod Length 6.800 - 10.150" DH  0 Deck  1.2250 Piston CH Stroke 4.250
Rod Length 6.800 - 10.170" DH  0 Deck  1.2450 Piston CH Stroke 4.250    
Rod Length 6.500 - 10.170" DH  0 Deck  1.6075 Piston CH Stroke 4.125
Rod Length 6.500 - 10.150" DH  0 Deck  1.5875 Piston CH Stroke 4.125
Rod Length 6.500 - 10.150" DH  0 Deck  1.7600 Piston CH Stroke 3.780
Rod Length 6.500 - 10.170" DH  0 Deck  1.7800 Piston CH Stroke 3.780