Blockage in Holley Baseplate Passage

Keystone · Feb 24, 2020

I have a question about a throttle body / baseplate on a Holley that I'm in the process of rebuilding. The list number is 80457-3 which makes it a 4160, 600cfm.

I have it all torn down, but I noticed something that looks odd on the baseplate. When looking at the passages to the outside of the bores, the one on the... (not sure why it's rotating my picture) but at the top left (which would be the primary on the passenger side) has a blockage in the casting.

You can see there is something in the secondary end of the passage on the same side, but it's broken out:

Same with the two on the opposite side:

So is this how this one is supposed to be?

I went to Holley's site and found the 112-113 part listing, and the image shows all the passages as open, but I do realize they may be using a generic image for all the throttle bodies.

Holley 112-113 Throttle Body Kit, 0-80457

And if this is a dumb question, my apologies. This is my first carb rebuild.

Mattax · Feb 24, 2020

Keystone said:
I have a question about a throttle body / baseplate on a Holley that I'm in the process of rebuilding. The list number is 80457-3 which makes it a 4160, 600cfm.

I have it all torn down, but I noticed something that looks odd on the baseplate. When looking at the passages to the outside of the bores, the one on the... (not sure why it's rotating my picture) but at the top left (which would be the primary on the passenger side) has a blockage in the casting.

View attachment 1715476408

You can see there is something in the secondary end of the passage on the same side, but it's broken out: View attachment 1715476409

Same with the two on the opposite side:
View attachment 1715476416

So is this how this one is supposed to be?
View attachment 1715476414

I went to Holley's site and found the 112-113 part listing, and the image shows all the passages as open, but I do realize they may be using a generic image for all the throttle bodies.

Holley 112-113 Throttle Body Kit, 0-80457

And if this is a dumb question, my apologies. This is my first carb rebuild.

Good observation.
Take a look at where the passage leads.
It takes fuel from the primary idle systems to a secondary idle port.
On your carb, and most carbs, there is no secondary idle port drilled in to this connecting passage.
This secondary idle port was drilled on a few list numbers. I think one may have been a production carb.
Having them slightly improves fuel distribution when needed.
Fuel distribution at idle depends on strong manifold vacuum. On setups with somewhat weaker vacuum the extra ports can help.

Keystone · Feb 24, 2020

Ah, good idea. Ok, so I used a flashlight and found the ends of those passages go to ports that are just under the throttle plates. So the one in question is here:

The ones for the secondary side are tiny:

MOPAROFFICIAL · Feb 24, 2020

There was a big explosive argument about this years ago on how a lot of carburetor still had the idle orifices or idle feeds in the secondary that they were not adjustable but they were still there which made it more important where are the secondary throttle Blade position was set.

None the less, if you only have 2 idle screws up front....dont worry about it.

Keystone · Feb 24, 2020

MOPAROFFICIAL said:
None the less, if you only have 2 idle screws up front....dont worry about it.

That's what I needed to know. Thanks.

Mattax · Feb 24, 2020

Keystone said:
The ones for the secondary side are tiny:

Open up the secondary throttle a little more and you'll see these tiny ports are in line with the transfer slots.

On the primary side, the idle ports are offset. On most Holleys, the idle fuel is taken from the down channel by a horizontal passage with mixture screw forming the control valve.

Looking from the bowl toward the body....
Outer holes go the the idle ports (primary side)