What is this Carter BBD port for?

[67CBodyGuy]

I have this carb on my 318. Yes its a china clone of a Carter BBD. I think it's a "Super 6" carb? I could have bought the clone of the older BBD version which would have matched what I had originally, it has fewer ports. Any ideas which one works better on a 318?

Anyways, when I want a measurement of manifold vacuum I use port 4, otherwise it's capped. But when idling, if I remove the cap, engine RPM goes up a little. Should this port be routed to the nipple on the underside of my air cleaner? I've got nothing connected to it currently.

I have 3, 7 and 8 (and 4) plugged. 6 is not plugged but not connected to anything. 5 goes to the distributor. I'm wondering what 8 and 4 are for, and should 4 be open somehow because RPM goes up when its open.

 

[Dana67Dart]

What year CAR are you working on?
What engine modifications?
What ignition (point, electronic, aftermarket) what brand?
What year Engine is the 318?


If rpm goes up due to a vacuum leak ( taking the cap off a port) it could indicate that the idle is too rich otherwise a vacuum leak would cause the mixture to lean out and the engine would run rough.


Keep in mind that a vacuum leak is the equivalent of opening the throttle blades a bit. But with out the benefit of the air going through the carb the correct way.

I assume you have tested all the vacuum ports under idle, part throttle and full throttle conditions.

That will tell you a lot about what each does.

If you have a flapper on your air cleaner to control heated air coming off the exhaust manifold you will need to consult the FSM as to what type of vacuum signal it needs.


Basically if a port is at full manifold vacuum at idle it's likely tied directly to the plenum in some way.

If it has 0 vacuume at idle but increases as the throttle is opened it is a ported vacuum but it might not be the correct one for vac advance depending where it comes from in the carb

 

[67CBodyGuy]

What year CAR are you working on?
What engine modifications?
What ignition (point, electronic, aftermarket) what brand?
What year Engine is the 318?


If rpm goes up due to a vacuum leak ( taking the cap off a port) it could indicate that the idle is too rich otherwise a vacuum leak would cause the mixture to lean out and the engine would run rough.


Keep in mind that a vacuum leak is the equivalent of opening the throttle blades a bit. But with out the benefit of the air going through the carb the correct way.

I assume you have tested all the vacuum ports under idle, part throttle and full throttle conditions.

That will tell you a lot about what each does.

If you have a flapper on your air cleaner to control heated air coming off the exhaust manifold you will need to consult the FSM as to what type of vacuum signal it needs.


Basically if a port is at full manifold vacuum at idle it's likely tied directly to the plenum in some way.

If it has 0 vacuume at idle but increases as the throttle is opened it is a ported vacuum but it might not be the correct one for vac advance depending where it comes from in the carb

1967 Dodge Monaco (a C-body) with a 318 (not very common in the C-body world).

I could list the P/N's for the heads, the intake, the block. The block dates from 1978 I think. The intake from 1968. The car originally had a 318 poly.

I was thinking the same thing about taking off the cap at port 4 and the effects on mixture and rpm. I haven't measured the vacuum or connected a vacuum gauge to any other port on this carb except 4. The choke and distributor and PCV are connected to their respective ports so I don't need to do any detective work for them.

I'm only wondering about the "extra" ports and what they go to on other car models from more recent years I presume. And it's not even that - I don't care about the EGR ports or the vapor canister ports (which I presume are 3 and 6). I just want to know about 4, and possibly 8.

 

[Dana67Dart]

Do you have a factory service manual for a 67 Dodge. Mymopar.com has them free.

IMHO

I would set it up using the info for a 67 273

Not much smog control in 67 other than the CAP stuff which is mostly dist curve and timing and a valve to slow the return to base timing on deceleration.

That being said. I would cap off all ports that are not currently in use.

 

[Vaanth]

The port fittings in the pictured carburetor are used as follows:

1. A full flow manifold vacuum port. Used on ~1979 and later for the brake booster due to other vacuum fitting complexities. Not needed for 1967. Cap if not used.
2. Metered vacuum to the choke pull-off as shown.
3. A full flow manifold vacuum port. Connect to the PCV valve if not connected elsewhere. Otherwise capped.
4. Vacuum for the air cleaner flap(s). If the air cleaner has a temperature sensor, connect to it; if no sensor, connect to the hose(s) that leads to the flap actuator(s). 1967 models were not originally equipped with exhaust manifold pre-heat and air flaps in the air cleaner. Likely a 1970 or later air cleaner has been installed.
5. Ported vacuum for the distributor vacuum advance.
6. Bowl vent. For 1967, this was not a tube like this but a lift valve that opened to the atmosphere. On my carburetors that are open fittings, I fit a small open mesh screen filter. If using a charcoal canister, connect to its vent port. If using a 3-port 1970-72 valve cover breather, connect to the 3/8" port on it. Do not cap off. It will hamper fuel flow if capped.
7. If this is smaller than 3/8", it is the purge vacuum for an evaporative charcoal canister on 1973 and later. 1967 models were not originally equipped with canisters. If one is installed and plumbed, connect to its purge port. If it is 3/8"-11/32", it is the PCV port. Connect to the PCV valve in this case. Otherwise capped.
8. Venturi vacuum sense port for EGR, 1973 and later, Not used for 1967.

Port 4 is a good source for your vacuum gauge when testing. The idle increases when the port is opened due to the increased air flow. This may not indicate any issue, but could indicate the idle mixture is otherwise a little rich. Set the idle settings with your vacuum gauge connected, and it will be essentially the same when capped, or nearly the same when connected to the air cleaner assuming a good sensor, if used, and actuator.

This clone carburetor looks like it's modeled after the late 70s Carter, and intended for semi-universal use. If they offer an earlier clone style, it likely has less fittings and may be jetted a bit richer, but this should be workable on most stock or near stock 318s.

The 318 was the base engine in many C-bodies, particularly low line models, polysphere through 1966 in the US, and 1967 in Canada, and LA thereafter through 1970. The 360 became the base engine in many after that. For tuning the LA 318 in your 1967 Canadian Monaco, check against the 1967 US LA 318 settings, although the polysphere settings are likely close enough.

 

[67CBodyGuy]

This is the bottom side of my air cleaner:

I can't be the only one with a fitting like this on a 318 with a BBD. I didn't measure the OD, it's either 3/16 or 1/4. It just opens into the air filter space on the other side. It's larger than the tube (port 4) on the carb, maybe with some struggle it's possible to connect them with the same tubing.

I cold-started the engine today with that port (port 4) open, wow did the engine like it. I'd have to dial down the fast idle setting if I keep it that way.

The 1967 Dodge Monaco / Polara factor service manual (which I have) shows WW3 Series Stromberg (272, 273, 274 and 275) being used with the 318 (auto, standard, CAP, non-CAP). This car did not come with a Stromberg when it was new, with the poly 318. It came with a Carter (AKA Ball and Ball?) BBD.

The lubrication and maintenance section shows an exploded view of the air cleaner and filter, it does not show this port.

 

[Dana67Dart]

The 1967 Dodge Monaco / Polara factor service manual (which I have) shows WW3 Series Stromberg (272, 273, 274 and 275) being used with the 318 (auto, standard, CAP, non-CAP). This car did not come with a Stromberg when it was new, with the poly 318. It came with a Carter (AKA Ball and Ball?) BBD

That's referring to the poly 318...

Different bird.

That's why I recommend you base things on the 273.