BBD question.

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volaredon

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I have an NOS BBD that I bought a while back, a guy on the other /6 forum had about 10 of them. (He sold out of them)
Carb number 6537
It's a 318 spec carb.
I had bought 2 of them, wish now I'd have gotten 3.
I put 1 on my son's truck when we super 6'd it.
I have 1 for mine.
And I have another vehicle here I wouldn't mind one for , that one actually has a 318.
Anyways
These carbs have little like "Pinholes" in the throttle butterflies, 1 hole in each barrel.
I also have a few older BBDs here, that are currently collecting dust.
Among the used ones I have around,
1 has the Pinhole In both sides.
1 has a pinhole in 1 barrel but not the other.
And the 3rd used one doesn't have pinhole in either barrel.
All these are 318 spec carbs, don't have the numbers handy.
I remember reading somewhere that it was a "318 thing" and that somehow those holes in the butterflies would not allow that carb to run right on a /6.
I remember when we put the one on my kid's truck, I mixed up some J-B and smeared over the holes.
It ran great. He has since sold the truck, I wish I knew then when I did the work for him that he was gonna do that. But IDK how well the J-B will hold up to a constant spray of gas going thru the carb.
But about the holes in the butterflies/ will they hurt anything if left as they are? Or do they have to be plugged for /6 application?
I thought about zapping them with my mig if so to seal them up/ or else swap those butterflies with the ones in one of my dust collector BBDs that don't have holes.
But being as how this is a brand new carb, and those butterfly screws are staked, I don't really want to be trying to take them out.
If it matters, the /6 in my kid's truck was stone stock, unrebuilt and a stick in a short bed. Unknown gear.
mine is fresh rebuild, reground cam, head and block ground for compression, bigger valves,
727, and a long bed with a 3.21. not gonna rehash the details right now, of the build. as if that may matter regarding a correct answer. What was the purpose of the holes in the butterflies?
 
If anything, the holes will lean the carburetor just enough so it's perfect. Bolt it on and go.
 
Actually the holes are to alter the idle air flow/speed, without having the throttle blades open too far, so the transfer slots are not in the correct relationship to the blades. I would try the carb as is (with the holes) and see if you can adjust the idle speed and mixture, properly. Then drive the vehicle, and see if the transition is smooth. If the idle speed is too high, with the speed screw all the way out, you will need to plug the holes.
 
Charrlie_S said:
Actually the holes are to alter the idle air flow/speed, without having the throttle blades open too far, so the transfer slots are not in the correct relationship to the blades. I would try the carb as is (with the holes) and see if you can adjust the idle speed and mixture, properly. Then drive the vehicle, and see if the transition is smooth. If the idle speed is too high, with the speed screw all the way out, you will need to plug the holes.
Click to expand...
If needed, what comes out of a tube that could plug the holes?
 
I used J-B weld on my son's carb,I think it was still there when he sold the truck but no way of knowing now. I used that thinking that I might want to remove it some day and open those holes again.
 
Haven't finished the exhaust on mine past the tube headers yet and haven't had the air cleaner on it. As it sits, mine idles at 800 RPM with the idle screw backed all the way out. I was wondering if I should be looking for a vacuum leak when I found this thread...

JB Weld is magic stuff! What do you guys think of a small screw and nut to plug the hole? I forget what they call securing a nut on. Staking?
 
JB Weld is not impervious to gasoline. Never has been, never will be. It WILL let go sooner or later.
 
holes are smaller than the smallest of screws/bolts I have ever seen. I wouldnt go enlarging them for the sake of being able to do as you're saying.
800 idle doesn't sound too bad. Where's your base timing set? that can also play a part.
 
RustyRatRod said:
JB Weld is not impervious to gasoline. Never has been, never will be. It WILL let go sooner or later.
Click to expand...
that's what I'd thought. didn't remember. At the time I had applied it to the holes on the butterflies on the kid's carb I wasn't sure I was doing right by sealing them, so I wasn't wanting anything permanent anyway. At worst I was thinking I could pull the carb and buzz off the J B with a Dremel easy enough.....
 
volaredon said:
holes are smaller than the smallest of screws/bolts I have ever seen. I wouldnt go enlarging them for the sake of being able to do as you're saying.
800 idle doesn't sound too bad. Where's your base timing set? that can also play a part.
Click to expand...
When I had the Hollley 1920 on it, I think it was around 4 deg BTC.
 
Duggie said:
Having anything in the throat of the carb that could get sucked into the engine makes me nervous!!:eek:
Click to expand...
I think JB Weld would get sucked and blowed with no damage. lol
 
RustyRatRod said:
I think JB Weld would get sucked and blowed with no damage. lol
Click to expand...
If it was a patch that wouldn't kill my car, I'd just reapply it when needed. Seeing metal bend/warp when welded makes me nervous about having someone weld the holes over and ending up with warped butterflies.
 
Duggie said:
If it was a patch that wouldn't kill my car, I'd just reapply it when needed. Seeing metal bend/warp when welded makes me nervous about having someone weld the holes over and ending up with warped butterflies.
Click to expand...
I'd trust a small bolt and nut with red locktite.
 
That hope is so small all it would take would be a quick zap to each one, the holes are about the diameter of the mig wire. Not enough to worry about warping anything. Some guys could do it without disassembly but when I cover my face with a dark shield my aim with the welding stinger ain't the best so I'd probably grind the stakes off and remove the butterflies. The small smear of J B is probably the safest.
 
I would just solder the holes shut if you need to.
Of course use a soldering iron or gun, not a torch.

Don't even THINK of mig welding them!
 
Yeah I know what you mean, especially if it's a used carb that may still have some fuel residue, be better if you're gonna weld them to pull the butterflies out and don't so. But mine has never had gas thru it yet. Just took it out of the box.
 
I went with the JB Weld on the butterfly hole. I did a lite scuff of the area, cleaned it with rubbing alcohol, and gave it a dab. Idle can now be set to the 650RPM factory spec.
IMG_8673.jpg


Got the Clifford headers and pipe welded back to a Y at the transmission cross member and took it for a spin. Stumbles real bad from a stop for the first five minutes. Doesn't stumble at all revving it from idle while in neutral. All I did was bolt it on and set the choke linkages. Guess I'll go back and look at the float, accelerator pump, and any other settings listed in the Motor Manual after I finish opening up the rocker arm oilers...
 
That carb looks like one of mine, hole only in one barrel.
Pop those limiter caps and either hook up a vacuum gauge and/or tach and adjust the mixture screws for highest reading you can get.
When I got my 83 D250 (318, but would apply to any engine) it had plugs over the mixture screws that were in a recess. I removed the plugs so I could access those mixture screws and got my best readings and performance with them 3/4 turn farther open than they had been set at the factory an those plugs driven in. Better mpg too. Your results may vary. All engines don't run their best with exactly the same settings as another.
I still have the original intake and carb from that engine. I had later swapped to a 4 barrel intake and carb. For what it was that engine didn't run too bad with that carb, it's a Holley 2280.would directly bolt on in place of a BBD.
If I don't get to the manifold carb and cam swap on my fury, I will probably put a kit into that carb and use it when I delete the lean burn system for now.
It's original carb is a 2280 that lacks a hose barb for a vacuum advance can.
 
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