Carter BBD 8146S 2bbl. bought it from someone (maybe on here/dont remember) & finally got it soaked & just about ready to go together & noticed a hole in each throttle plate, [ Moparts Family Site - Keep it Friendly ] I thought that was a wild cam mod & only valid in some cases. they are .106" and appear to be drilled in the same exact spot in each plate (OE as opposed to hand drilled??) Your thoughts please. this is going on a DD /6 & if I need to solder em up now is the time. thank you for your time.

I haven't heard of extra holes on a production engine either. In any case, I don't think a /6 with moderate cam would like the vacuum leak created by the holes. Best to close them up.

I would suggest doing a bit more research on the particular carb/ application before closing the holes. I have seen factory applications that do have the holes as designed.

Tim yeah I guess I could toss the carb on with no sealer on the base gasket then pull it & cement it after deciding if it needs soldering or not (if it runs OK) but it would be easier to get it right ahead of time. Something about the precision of the holes my gut is telling me that it is factory. Ahy, agreed I had never seen that before & just happened to look down into the box of cleaned parts on the kitchen floor on a midnite trip to the frig a day ago (& it is a OE cam DD) & thought WTH. I will Google the number & see if the year/app tells me anything & if no go Scott Harms WILL know! thanks guys!

I have see some BBD carbs with the drilled blades. It's been a long time since I played with 2 bbl carbs, but I seem to recall it was an emissions thing. They were trying to get the idle leaner.

for some reason i recall that too. maybe on K-body stuff? i had several of them

I'd run the carb before making any changes.

Ding ding ding I do believe we have a winna (& I was all set to solder em as I just want it to run so I can move (drive) it around the garages here). then I will know if the (OE) setup worked well or not) which is good to know

That carb is from a 78 pickup 318, I had several. The holes are common. Jeep CJ's used the same carb and they have the holes too. Tim

Alright, it is going back together as is

The carburetor installed on 1973 318 Auto (California) engines is a BBD-6344SA and it has holes in the throttle plates. I installed one on my 67 318 and was unable to reduce the idle speed below about 700 RPM due to those very holes. Since this was a California carburetor, the throttle plates were probably drilled to compensate for a small amount of EGR flow at idle.

& I just had my mind made up! (to leave em be)

Part of the reason for the holes is because of how Carter did the holes for the idle mixture and transition, I had a 318 idleing at 550 rpms with this exact same carb. Plan on a rebuild every year, they don't like any junk to build up in them. I still have 1 similar on the shelf if I ever need it for a jeep project. Tim

Many of the engines in the 70's when there was alot of mods done for emissions would have the timing retarded and they would turn the idle speed up some to let more air in at idle so that may be one reason they did it. I seem to remember seeing the holes also. I have seen new Holley 4 barrel carbs with the holes in the throttle plates also. Ron

BBD carbs wear out the throttle shaft bores in the baseplate too. That leads to idle issues too.