Plugs and holes in the 400 B-block intake runners?

[HombreCalgarian]

Looking down into my 400 intake I see a (newish-looking) plug in one (upper) half and there is a round hole and some cavity in the lower section. What are these for, any ideas?
Thanks!

 

[Big_John]

EGR

Exhaust gas recirculation for smog control. Consult your FSM for more details.

 

[HombreCalgarian]

EGR

Exhaust gas recirculation for smog control. Consult your FSM for more details.

Thank you!

 

[1970FuryConv]

EGR

Exhaust gas recirculation for smog control. Consult your FSM for more details.

Is there logic to plugging one side and not the other on a dual plane intake?

 

[Big_John]

Is there logic to plugging one side and not the other on a dual plane intake?

When you have an EGR valve on the top of the manifold, you just block the ports by the valve (with a flat plate) and that accomplishes the same.

 

[1970FuryConv]

On the 400, I'd plug them both.

On the others, that have an EGR valve on the top of the manifold, like a 440, you just block the ports by the valve (with a flat plate) and that accomplishes the same.

Agree with plugging both sides to achieve same air/fuel mixture quality on both sides.
Previous owner only plugging the upper port makes no sense.

 

[Big_John]

Agree with plugging both sides to achieve same air/fuel mixture quality on both sides.
Previous owner only plugging the upper port makes no sense.

I had to walk back what I said about the difference in the 400 and 440. Both can be bypassed by blocking the EGR valve. Minor brain fart... The EGR valve is just activated differently.

But anyway.... What looks like a plug is a "jet". Why they (Chrysler) only put it on one side is a little beyond me, but that's the way I've seen them.

Here's a couple:

 

[HombreCalgarian]

I had to walk back what I said about the difference in the 400 and 440. Both can be bypassed by blocking the EGR valve. Minor brain fart... The EGR valve is just activated differently.

But anyway.... What looks like a plug is a "jet". Why they (Chrysler) only put it on one side is a little beyond me, but that's the way I've seen them.

Here's a couple:

View attachment 553882

Another one I found on the interwebs...
Anyhow, I will plug them all + the heat riser, since I have Holley Sniper EFI and all these chambers and orifices and exhaust leaks just drive its brain crazy.

 

[fury fan]

Another one I found on the interwebs...
Anyhow, I will plug them all + the heat riser, since I have Holley Sniper EFI and all these chambers and orifices and exhaust leaks just drive its brain crazy.

Give some more consideration to NOT blocking the heat riser passage. It functions to warm the intake manifold and help keep fuel atomized, and without it you might get some more fuel wetting of the manifold. Although EFI will compensate for pulling residual fuel off the walls, in my non-expert opinion any EFI setup that sprays fuel above the throttle blades would benefit from a warmer intake. Esp as I see you are in Canada. Although with EFI, it's simple enough to try it both ways, as the ECU will relearn the difference. Maybe there is no difference...


@Big_John
Can you explain the difference on EGR valve actuation between 400 and 440? I would have presumed both would be the same. ???
In recent years I've wondered how well a custom-controlled EGR system would work. (increased timing via MSD module, elec vacuum valve, master control switch, etc)

I had to walk back what I said about the difference in the 400 and 440. Both can be bypassed by blocking the EGR valve. Minor brain fart... The EGR valve is just activated differently.

But anyway.... What looks like a plug is a "jet". Why they (Chrysler) only put it on one side is a little beyond me, but that's the way I've seen them.

Here's a couple:

 

[Big_John]

Can you explain the difference on EGR valve actuation between 400 and 440? I would have presumed both would be the same. ???
In recent years I've wondered how well a custom-controlled EGR system would work. (increased timing via MSD module, elec vacuum valve, master control switch, etc)

The best explanation comes from the FSM. In this case, I pulled up the '73 Dodge chassis manual from MyMopar.

One caveat... I'm really only familiar with the '73, so other years may or may not be the same.

 

[HombreCalgarian]

The first couple of hundred miles with the new setup - there is no differnce, cold or hot. So will keep it this way for now. Thanks everybody for inputs and comments!

 

[1970FuryConv]

The first couple of hundred miles with the new setup - there is no differnce, cold or hot. So will keep it this way for now. Thanks everybody for inputs and comments!

So is the EFI still having brain problems?

 

[HombreCalgarian]

So is the EFI still having brain problems?

The EFI never had any, rather it was my struggle to fathom out all the nuances of its setup - which is rather poorly documented by Holley.

 

[1970FuryConv]

Got it. Vague directions, where you are assumed to be a tuner/expert/etc, are frustrating