Holes drilled in carb?

[Coralsnake]

https://www.ebay.com/itm/1968-SHELBY-HOLLEY-CARBURETOR-GT500-MUSTANG-428-C8ZX-9510-A-LIST-4129-DATE-7A4/233184834962?epid=4015343161&hash=item364ae63592:g:9C8AAOSwbv9coT79

I have a couple of carbs that have the same holes drilled i to the back of the air horn, can anyone advise the purpose?

[KR Convertible]

Doesn't seem to make sense.  Usually, those small brass tubes go down into the primaries and supply vacuum to actuate the secondaries.  I had two of those carbs dated 7A4, neither had those holes.

[67_1183]

From the "full item description":

FOR SALE IS AN ORIGINAL SURVIVOR 4129 HOLLEY CARBURETOR.  IT FITS EARLY 1968 SHELBY GT 500  WITH A 4 SPEED OR AUTOMATIC TRANSMISSION.  IT IS DATED (7A4) 4TH  WEEK OF NOVEMBER 1967.  THE FORD PART NUMBER IS C8ZX-9510-A.  IT HAD THE COMMON MODIFICATION BACK IN THE DAY WHICH WAS AN ADDED SQUIRTER TO THE SECONDARY.  RATHER THAT FILL THE HOLES AND RESTORE IT I OPTED TO LEAVE IT TO SHOW THAT IT WAS ORIGINAL AND NOT A RESTAMP.  ALSO, TO VERIFY ITS THE REAL DEAL THE ORIGINAL AUTOLITE TAG IS STILL PRESENT.  I ADDED A NEW CROSS OVER TUBE AND INLET FILTER TO MAKE IT COMPLETE.   I ALSO HAVE ANOTHER CHOKE PLATE THAT WILL BE INCLUDED IF THE BUYER CHOOSES TO RESTORE IT.  IT HAS BE IN DRY STORAGE FOR YEARS AND WILL NEED REBUILT.  IF YOU HAVE ANY QUESTIONS PLEASE DO NOT HESITATE TO ASK.

[KR Convertible]

I guess I should have read the full description.  I only looked at the pictures.

[68blk500c]

I have a couple of carbs that have the same holes drilled i to the back of the air horn, can anyone advise the purpose?

I have heard lore that is was on old school/performance attempt.  Doesn't seen to make sense, though. 

[gt350hr]

   Pete,
      Back in the day , Segal Manufacturing made a kit to convert a vacuum secondary ( most at the time) to mechanical operation. Part of the kit was an accelerator discharge nozzel  ( squirter) that had extended tubes to squirt into the secondary side of the carb to avoid the "bog" caused by going to mechanical secondary operation.  This required the two holes to be drilled and allow the extended nozzel to function. Other companies followed suit and this modification was done to many performance carbs. Other than the visual aspect it does no harm to the operation of the carb.
   Randy

[OldGuy]

   Pete,
      Back in the day , Segal Manufacturing made a kit to convert a vacuum secondary ( most at the time) to mechanical operation. Part of the kit was an accelerator discharge nozzel  ( squirter) that had extended tubes to squirt into the secondary side of the carb to avoid the "bog" caused by going to mechanical secondary operation.  This required the two holes to be drilled and allow the extended nozzel to function. Other companies followed suit and this modification was done to many performance carbs. Other than the visual aspect it does no harm to the operation of the carb.
   Randy

Randy is correct. In addition to the squirter nozzles, the "kit" that I had provided washers (that were used as spacers) that were inserted between the cap and the diaphragm on the vacuum secondary servo that nullified any opening/closing action AND 90° meshing spur gears that were attached to both of the throttle shafts (passenger side of carb) after removal of the factory linkage.

These mods were to provide simultaneous opening of both the primary and secondary throttle plates and provide a "squirt" of gas to all throttle bores. Did it work? It worked ok on a sky boat that I once had but was not really street worthy unless the throttle was rolled on slowly. If you nailed it at low speeds you usually killed the engine due to the in-rush of air.

I still have the Holley that I ruined by providing these modifications. The things that were done in the '70's.

Frank 

[Coralsnake]

Thanks much appreciated

I have heard they could be welded, but I havent found that guy yet

[Bob Gaines]

Thanks much appreciated

I have heard they could be welded, but I havent foun$ that guy yet

I had some squinter holes repaired before . At the time pony carbs handled it. some of the miracle soldering flux products you typical see at bigger swap meets ,online etc. are supposed to solder diecast  . I bought some at the Carlisle swap meet (don't remember the name) and it worked on a diecast statue that I repaired. I assume a product like that was used to repair my carb but haven't tried it on a carb myself yet

[Dan Case]

Zinc die castings can be TIG welded if you can find the correct alloy filler rod. In the early 1980s we fixed anything we could instead of replacing it. We had a broken 1966 Mustang casting that held the left side head lamp bucket.  I friend that worked for a NASA contractor at the Marshall Space Flight Center welded it up and we did the preparation for paint. Turned out great and the car's original part was still in use during its years as a trailered MCA show car.

No, at this time I have no idea where to get appropriate filler rod.

[gt350hr]

  Google Cecil Muggy for the special filler rod needed for "pot metal". IF you are going to try it yourself , practice on a scrap carb to perfect your technique BEFORE attempting to do a rare carb. "Pot metal" is tricky to weld/solder , but can be done with practice. The gold dichromate "may" not color the same on the repair , showing it was repaired. Since there is zero effect by having the holes , "I" leave them alone.
   Randy

[Bob Gaines]

  Google Cecil Muggy for the special filler rod needed for "pot metal". IF you are going to try it yourself , practice on a scrap carb to perfect your technique BEFORE attempting to do a rare carb. "Pot metal" is tricky to weld/solder , but can be done with practice. The gold dichromate "may" not color the same on the repair , showing it was repaired. Since there is zero effect by having the holes , "I" leave them alone.
   Randy

The tricky part as mentioned is that the "pot metal " body of the carb can actually melt during the heating up process of adding the flux and rod to solder up the holes. To re color you have to electro plate the entire carb body soldered portion and all with a layer of zinc so that the zinc dichromate (gold) will  color everything evenly.

[gt350hr]

    +1 Bob ,
        I use a map gas fueled "torch" rather than acetelyne. The heat needs to be enough to melt the "solder" but not compromise the pot metal. That temp is "around" 300*s IIRC. The pot metal must melt the solder , not the torch , and that is what makes it tricky as pot metal melts a couple hundred degrees higher.
    Randy

[Pcunder]

I bought a 70 Boss 302 carb with the same holes and was going to try the Muggy Weld method.

Luckily, before I did, I ran across a guy on EBay that did a decent job of repairing the holes and refinishing the rest of it. No, it wasn't a show quality finish and there were a few minor things I nit-pic'd but, for $250 or so, I was pleasantly surprised...

I think he filled the holes with some kind of 2-part epoxy before the replating...which obviously doesn't match in that area...but I think it's far better than before. Attached is a pic before plating.

Anyway, he said he worked for Pony Carbs in NY before they moved to NM.
He goes by 'carbontooters1' for his EBay ID.

Phil

[dieseldave]

I have a BOSS 302 that had the extra holes in it. Had a welder TIG weld it. The repaired area is a different color after plating.