3269 3461 AFB Carter Carburetor

[Cecil L.]

Re: 3269 3461 AFB Carter Carburetor

I think we are all convinced that it wasn't the drilled passages over the secondary throttle shafts causing your problems, but out of curiosity, i dissassembled my 3460S dated J2, to see if it had the holes. sure enough, it did, so it can't be a 340 hp thing. One hole is not drilled completely as where the drill bit broke through to the shaft bore, it just barely broke through leaving a small opening to the shaft. The other side was more completely drilled.
The original purpose of the holes is still unknown but apparently not a functional requirement.

[Clem Z.]

Re: 3269 3461 AFB Carter Carburetor

I think we are all convinced that it wasn't the drilled passages over the secondary throttle shafts causing your problems, but out of curiosity, i dissassembled my 3460S dated J2, to see if it had the holes. sure enough, it did, so it can't be a 340 hp thing. One hole is not drilled completely as where the drill bit broke through to the shaft bore, it just barely broke through leaving a small opening to the shaft. The other side was more completely drilled.
The original purpose of the holes is still unknown but apparently not a functional requirement.

i still think they are there as a vacuum break to prevent unfilter air from being sucked in along the shaft and maybe causing it to bind . JMHO

[Stuart F.]

Re: 3269 3461 AFB Carter Carburetor

Cecil;

Are the 3460 and 3461 perhaps using the same body assembly (w/ primary throttle shaft and arm)? I just wondered because I have seen some series (manual and Auto) just add the ball for the tranny link in an existing hole in the throttle arm and then we know, of course, they use different clusters and jets. I have also seen some with a hole in the arm for a return spring and some without.

I think the holes are for adding 3 in 1 oil put there so some rebuilder can say; "and yep, I also oiled your secondaries", Ha! Some one out there probably knows and when they tell us we'll all say; "oh yaaa! why didn't I think of that" or "I knew that all along", it's like a core hole.

Good Night;

Stu Fox

[Timothy B.]

Re: 3269 3461 AFB Carter Carburetor

I wanted to report results of the test today on the 3461 idle problem.

I removed the stainless shield and used another base gasket in place of the shield so the arrangement is gasket, heat spacer, gasket then carburetor. The engine runs exactly the same so I don't believe the problem is a vacuum leak around the base.

I slowed the motor some be modifying the internal spring on a spare PCV valve I bought for the car some time age. It only passes a very little air at idle and this slowed the engine 1-200RPM. I am not sure how the valve will function under load as the internal spring may not push to allow good air flow through the valve. The motor may be idling around 6-700 now but I still don't feel it's right. I noticed the closed primary throttle blades show very small transfer slot exposure, this may be the next thing I focus on.

Unless someone can suggest something else, I'm stumped.. I have a 3721SB I can build to see if it eliminates the engine as a problem. If it turns out to be the 3461 I just don't know anymore, maybe I will just live with it..

When I questioned a carburetor rebuilder last week about the small holes in the secondary throttle shaft bores we are talking about above, he stated they are to initiate flow in the secondaries. I really don't understand that because the 3721 uses the same part # secondary booster venturies but without any holes in this location so it does not need help starting secondary flow.

Sorry for my long winded post..

[Stuart F.]

Re: 3269 3461 AFB Carter Carburetor

Thanks for the update Tim. I agree that you should build your 3721SB and give it a try to at least narrow the problem to either the engine or the 3461S.

I can't understand your rebuilder friend's opinion about the drilled holes either. I'm inclined to believe he didn't understand what you were talking about, but didn't want to admit it. Holes drilled into the shaft bore, and for all intents blocked off from a chamber that should have nothing in it but unpressurized filtered air, could not possibly influence fuel or air flow. Actually, I like my 3 in 1 oil hole explanation better.

Stu Fox

[Stuart F.]

Re: 3269 3461 AFB Carter Carburetor

Tim;

Is it possible that your rebuilder friend was referring to the "initial discharge ports" which are located next to the venturi struts at approximately the level of the secondary air valve. That would make more sense, rather than the holes into the bores of the secondary throttle shaft.

Stu Fox

[Timothy B.]

Re: 3269 3461 AFB Carter Carburetor

Hi Stu,

Your statement sounds like what this rebuilder is refering to but I was very descriptive when describing the location of these holes.

Next week I am going to remove the lid and check the duct tape over these holes to see if it's been sucked open. I will also post some pictures of the closed primary throttle blades to get everyones opinion if they think there is a problem here. The blades don't seem to close as far as the 3721 I have here in the basement.

After that