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.