Carb rebuild

[LEB Ben]

The secondaries are only going to open when conditions demand them to. Did you get on it some while driving it around?

Damn...forgot to ask the all important question. Have one more possible test you could do, and Tony, tell me if I'm right in my thinking. If he holds the primaries open and blows compressed air past the venturi, wouldn't this mimic the vacuum and cause the secondaries to open?

 

[surewhynot]

You're original problem is that the truck was running lean. Searching for that solution in the opening of the secondaries isn't going to be very productive. The secondaries won't open until the engine needs them. With the stock spring in there, on your 460, they won't even begin to open until around 2400 rpm and under a good load. You need to get the jetting right before worrying about the opening of the secondaries.

Take it out for a short drive, driving normal, without getting aggressive. Pull the plugs and look at them. If they are white, you need to go up in jet size. You are looking for a nice tan color.

Once you get to that point, then you can start tuning the secondary springs to get them to open when you need them to. I like to start at the lightest spring and work my way up. I put in the light spring, and if I can feel the secondaries kick in, I move up, until I can't. The reason is, when you feel the secondaries kicking in, you are actually feeling a lean bog, from the fuel trying to catch up from the secondaries opening too soon. Once you get the secondaries opening when they should, you can then check the plugs and see if the secondary metering plate (similar to jets) is right. You may have to go to a higher number to richen it up.

 

[surewhynot]

Damn...forgot to ask the all important question. Have one more possible test you could do, and Tony, tell me if I'm right in my thinking. If he holds the primaries open and blows compressed air past the venturi, wouldn't this mimic the vacuum and cause the secondaries to open?

Nope. Won't give it enough of a signal and also it requires the vacuum to come from the manifold. He really needs to concentrate on his lean condition before worrying about the secondaries.

 

[LEB Ben]

Looking at the diagrams in that pdf the big vacuum port on the back of the carb is labeled as brake booster vacuum - I have my pcv hooked up to this and brake booster vacuum coming off of the manifold, is this a problem?

Your setup is fine

Nope. Won't give it enough of a signal and also it requires the vacuum to come from the manifold. He really needs to concentrate on his lean condition before worrying about the secondaries.

All great info...I skipped right over the fact that he was running lean, you still might be useful after all...ahha.

 

[LEB Paul]

I understand what you're saying Tony, but it looks like the secondaries aren't opening either way.

It runs and sits just below 180* at idle for as long as I let it sit there, but as I drove it around it starts getting hot. I was driving it hard every time I drove it, but I can try driving it "normally" and seeing what happens.

 

[surewhynot]

Running on primaries only won't cause a lean condition if the carb is jetted right. The primaries and secondaries have there own respective enrichment circuits. (primary jets, secondary metering plate) You are definately gonna have to re jet.

As far as the secondaries not opening, the butterflies may be binding a hair. Underneath the carb, there is a small screw that stops the secondary butterflies from closing too far and binding. That may need turned out a hair. They may be binding enough to keep them closed, yet you still may not be able to feel it by hand.

Regardless though, get that thing running rich enough so you don't burn it up. With that being a 3310-10, I believe it has either #70 or #72 jets in the primaries. You are probably gonna need around a 76.

 

[LEB Paul]

okay, thanks again for the info Tony. Should I still drive around normally to see if it'll run lean then or should I just re jet it now? Should I be able to open the secondary butterfly by hand when it isn't running?

 

[surewhynot]

You should be able to open them by hand when its not running. You will have to open the primaries also, or the linkage won't allow the secondaries to open. The main concern I have is with it running lean, the more you drive it, the more of a possibility it is to damage it.

 

[LEB Paul]

Yeah, it gets hot pretty quick when driving. This is the motor in the Bronco, so there's no immediate need to drive it. It can sit until either the carb is rebuilt or I get the jetting changed. Here is a picture of the plug after it had been run pretty hard and started to over heat:

 

[surewhynot]

It may just be the pic, but that plug doesn't look excessively lean.

 

[LEB Paul]

That's the pic I sent to Karl and he concluded secondaries weren't opening causing it to run lean.. of course it was on his cell phone so maybe he couldn't see it right.

What else would cause it to overheat while driving but not at idle if you don't think it looks lean?

Radiator is clean, no mud in it...and it is huge.

Possibilities:
Water pump was not new
Piece of the fan shroud is missing .. cracked maybe an 1/8th of it gone.
maybe the fan clutch isn't working? is there a way to test that?

I am going to add an electric taurus fan to replace the mechanical fan, but I didn't want to introduce more variables before I got this over heating issue under control.

 

[surewhynot]

Secondaries not opening will not cause it to run lean if the primaries are jetted properly. Follow me on this-

If the secondaries not being opened could make it lean, then it would be lean at idle and when you are driving in a style that would cause the secondaries to not be open. The primaries and secondaries have their own respective fuel circuits. Running on primaries only may decrease power, but will not cause a lean condition. The secondaries add fuel AND air, not only fuel. They alone will not richen up the fuel mixture.

As far as the way the plug looks, I am looking at a picture. You will have to be a better judge than me. Is the plug an even tan color or is it whitish?

 

[LEB Paul]

No, I wasn't disagreeing with you - I was simply relaying what I was told. What you said makes sense. edit: Also, I mis typed - he said the secondaries weren't getting fuel - causing it to run lean, which does make sense right? If the butterfly is opening and no fuel is dumping in then it'll run lean or no?

I will have to pull the plug again to get a better judge on the color, that picture was taken a few weeks ago. I don't remember besides looking at the picture.

 

[surewhynot]

I know you aren't disagreeing. I'm just wanting to make sure that I am seeing the pic good. To me it looks tan, but in real life it may be whiter. It's hard to tell from 1000 miles away.

 

[surewhynot]

I have a hard time explaining things sometimes. I was just trying to give an example of my train of thought.

 

[surewhynot]

Also, I mis typed - he said the secondaries weren't getting fuel - causing it to run lean, which does make sense right? If the butterfly is opening and no fuel is dumping in then it'll run lean or no?

Well, your butterflies aren't opening so no worries there. Also, the dumping fuel you see is just the initial shot from the accelerator pump. It isn't what runs the engine, it just adds extra fuel to compensate for when the throttle blades are opened up. Fuel mists out (for lack of a better explanation) to run the engine.

 

[LEB Paul]

Okay, so tomorrow I should start it up, let it warm up, put around the block without gettin it - then I'll pull a plug and get a better picture for you. Sound like the correct next step from here?

 

[Proeliator]

You're original problem is that the truck was running lean. Searching for that solution in the opening of the secondaries isn't going to be very productive. The secondaries won't open until the engine needs them. With the stock spring in there, on your 460, they won't even begin to open until around 2400 rpm and under a good load. You need to get the jetting right before worrying about the opening of the secondaries.

Take it out for a short drive, driving normal, without getting aggressive. Pull the plugs and look at them. If they are white, you need to go up in jet size. You are looking for a nice tan color.

Once you get to that point, then you can start tuning the secondary springs to get them to open when you need them to. I like to start at the lightest spring and work my way up. I put in the light spring, and if I can feel the secondaries kick in, I move up, until I can't. The reason is, when you feel the secondaries kicking in, you are actually feeling a lean bog, from the fuel trying to catch up from the secondaries opening too soon. Once you get the secondaries opening when they should, you can then check the plugs and see if the secondary metering plate (similar to jets) is right. You may have to go to a higher number to richen it up.

Tony is dead on. The motor should run at on optimal a/f ratio on the primary circuit alone. The secondaries are there for power need, and in most causes with vacuum secondaries don't even fully open. He could block off the secondary system all together, and while his power would suffer it would not lean out his motor. This is why two barrel, and even single barrel carbs work just fine.

 

[LEB Paul]

Talked to Tony on the phone earlier, then we decided to drive it around. It took longer to over heat while not driving it hard, but it still did start to over heat. I had to get to work though, so didn't have time to pull the plug to check if it was running lean. Will do that tomorrow.

 

[surewhynot]

I tried talking him into sticking his hand in the fan blades to test the fan clutch, but he wasn't man enough.