Vacuum line routing?

[Baja71]

New motor, new distributor, new questions. ;D

Old distributor had two vacuum lines, one running to a separate Vacuum Advance Control Valve and then on to the carb, and the other one to the air cleaner (as I recall). New dist has only one port.

How do I route the new dist vacuum line and do I still need the separate Vacuum Advance Control Valve with the new dist, or is one incorporated into the attached valve?

 

[DirtDonk]

With the new single-port vacuum advance unit you will no longer use any of the extra valves, ports or hoses from the manifold. You can cap them off or remove them completely if you want.
Your new one will have a single hose running to the carburetor's "ported" vacuum port.

Which carb are you running? Depending on the carb, the correct port can be in different locations. Some are on the side, but most are facing the front probably. Usually you have two though. One is full manifold vacuum and the other is ported. That one only gets a vacuum signal after the throttle plates are opened up slightly.
If in doubt, it's often the higher up of the two ports. If nothing is obvious, then you may have to wait to get the engine running and check each one with a finger to see which one has vacuum all the time and which one is only part time.

If you post up what carb you have, someone here will most likely know exactly which one to use. I forget where they are on most carbs frankly.

Paul

 

[Baja71]

Hey Paul...always appreciate your replies.

I'm using a 4100 which only has the one open port in the same spot as a 2100 (under the hot air choke). I was suspecting that control valve would no longer be necessary but great to have confirmation. So, if I remove that control valve and run from the distributor directly to the carb, nothing runs to the air cleaner? No other vacuum lines?

 

[DirtDonk]

If you're still going to use the air-activated type valve on your air cleaner, then yes you'll still need to figure out some routing. But it'll come from the manifold with a heat-activated valve I would think, rather than sharing the system with the distributor.
Other than that, you'd have to swap the distributor back to the dual-diaphragm setup to keep the action the same as original.

If the carb is still off, you can look up inside the throttle bore adjacent to the blades to find a slot next to where your hose fitting is. It should be in a primary bore though, as the secondaries couldn't be used for that. It's a thin little slot probabbly about 1/4 to 3/8 inch long I'm guessing.

That would confirm that your port was "ported" rather than full vacuum.

Paul

 

[Baja71]

I'm going to use the stock 1971 air cleaner which no longer has any components attached...looking through baggies...

Here's a shot of the carb.

 

[DirtDonk]

That side port in the lower right is not the standard advance or accessory nipple. Looks more like the PCV port with a smaller hose barb fitted. Is that nipple a 3/8" or is it smaller?

See those three small holes just above the single hole where the idle-air screw tip fits? Those looks suspiciously like the vacuum advance ports. You sure there isn't a hose fitting somewhere adjacent to those? Maybe some compressed air will tell the tale.
I've never seen holes in place of a slot though. Every carb I've ever looked in had a slot.
Could this be off a muscle car originally by any chance? I wonder if that particular application lacked a vacuum advance from the factory? Not likely, but still possible I would think.

Got a wider view by any chance?

Paul

 

[Baja71]

Port size is 1/8" ID, 3/16" OD.

There is a plug above the air mixture screws on both primaries...both primaries have those 3 holes next to each other, plus an air mixture hole. The primary with the nipple has an extra "big" small hole.

 

[Baja71]

That side port in the lower right is not the standard advance or accessory nipple. Looks more like the PCV port with a smaller hose barb fitted. Is that nipple a 3/8" or is it smaller?

See those three small holes just above the single hole where the idle-air screw tip fits? Those looks suspiciously like the vacuum advance ports. You sure there isn't a hose fitting somewhere adjacent to those? Maybe some compressed air will tell the tale.
I've never seen holes in place of a slot though. Every carb I've ever looked in had a slot.
Could this be off a muscle car originally by any chance? I wonder if that particular application lacked a vacuum advance from the factory? Not likely, but still possible I would think.

Got a wider view by any chance?

Paul

That port fitting is in the exact same molded port position on my 2100, so I gotta believe it's for the same purpose.

Checked the air cleaner and there is no provision for any type of temp sensors that I can see. I'm thinking the '71s did not have this yet. There is a port for the evap canister paper hose. Also, a short rubber PCV hose off the bottom that goes into the valve cover port.

 

[TBS-POPS]

Yes, that is the vacuum adv port on the side next to the fuel inlet.

 

[Baja71]

So, back to the original question, what vacuum hoses will need to be installed on this new engine with one distributor port? Just one from the distributor to the carb? That's it for vacuum lines?

 

[adam05ford]

And one to the vacuum mod on the tranny

 

[adam05ford]

Do you have vacuum brakes? If so that large fitting on the back of the carb goes to it.

 

[Baja71]

I've got a manual trans, so I'm cool there, but you brought up a good point I wasn't thinking about since I had manual brakes too. I'm planning on installing a Tom's PB system which does have a booster. That main port on the back is the fuel input. I guess I need to know where to tap into for the power booster.

 

[adam05ford]

Any full manifold vacuum will suffice. If you don't have a large 1/2" vacuum port on the carb you will have to get it from the intake manifold itself.

 

[TBS-POPS]

There is a large port tube on the rear bottom of carb in center for the brake booster line. the fuel inlet is on the front and is a threaded port. Pic 1 and 4 post 7 to the left of the accel pump on front of carb.

 

[Baja71]

Right, threaded is the main fuel inlet, copy that. Are you talking about the port on the spacer plate? My PCV hose runs to that large port. I don't have any other ports on the carb. How about one of these instead for the brake booster?

 

[TBS-POPS]

Yeah thats fine. anywhere you can get full manifold vacuum. replace that block fitting with a straight hose barb fitting.

 

[jckkys]

The 4100 has ported vacuum advance port as your photo shows. The only other tubing barb supplies clean air to the automatic choke. That's all there is on any 4100. Some 2100-2150s have a PVC nipple on the back. Some emission distributors have both vacuum advance and retard nipples. Even if you have both, just connect the advance to the carb. It helps part throttle drive-ability and MPGs. The retard doesn't. It's only for emissions. The 4100 is a great carb. It's not an emission carb.So if you can run a 4100 you don't need vacuum retard, EGR, etc.

 

[jckkys]

After looking at your photos, I would suggest a Ford carb spacer with a PVC nipple in the back. The '71 had the PVC valve on right rear valve cover and the Ford aluminum 4 barrel spacers were perfect for this. They route the PVC or crank case fumes to the primary bores so it mixes with the fuel-air to be distributed evenly. They are a common early Mustang part. The vacuum block in your photo has a big hex drive plug that can be removed and replaced with a large 1/2" nipple for power brakes. Find diagrams for '65-'67 Mustangs with 289 4 barrel engines. They had 4100 carbs so all the info will apply to your engine.

 

[Baja71]

I do have the Ford spacer with the PCV port. My late 71 has the PCV valve in the front of the left valve cover and a hose that runs around the front of the carb, down the passenger side of the carb an around back into that spacer PCV port. The right back valve cover has the fresh air hose that comes from the air cleaner and supplies the 'intake' for the PCV system. Not sure why they changed the flow direction, but they must have done it mid year. I've seen others with the same setup. Here's a pic but I haven't sourced the PCV hoses yet. I can't find them as the other system seems more popular with the vendors.