Intake Question - 4bbl upgrade

[MKTSC]

67 Fury with a 400. Currently 2bbl Stromberg. Upgrading to a Thermoquad. I got a Thermoquad manifold, and noticed two ports that go from the exhaust crossover and exit directly under the carb. I made a blank-off plate for the EGR. Can I just tap and plug these holes or do they serve some purpose?

Thanks in advance,

-MK

 

[saylor]

highly interesting, never seen that before. we need someone old to enlighten us.

 

[MKTSC]

Also I see a lot of guys blocking the exhaust crossover. I'd think that would affect the operation of the thermostatic choke. Does anyone see any benefit to this for a stockish vehicle upgrading to a 4bbl?

 

[Darter6]

Yes, you can tap and install flush pipe plugs.The holes were for the EGR that you won't be using.Yes I'm old.......

 

[MKTSC]

Awesome thanks for the info. I figured it was for EGR, but wasn't 100%. Decided to get the valley pan and gaskets that do NOT block off the crossover though. I want my choke to work, and I'll just block off all of the EGR ports.

 

[Darter6]

Clean out the carbon in the cross over, looks like allot of buildup.

 

[MKTSC]

Yeah it's pretty nasty and I don't want to put that in the engine. You have any tried and true methods of cleaning intake runners?

 

[traintech55]

To clean the intake, I use a 1/4" drill bit on low speed and work the bit thru the carbon. Good move keeping the heat crossover passage, it is there to help the fuel on cars in cold climates. Also the E.G.R. block off plate will keep the manifold from leaking. And yes I am an old timer also.

 

[MKTSC]

How do you get all the way in each runner with a 1/4" drill bit? I think I'm missing something...

 

[traintech55]

How do you get all the way in each runner with a 1/4" drill bit? I think I'm missing something...

Everyone I have ever seen clog up is only about half way up the runner. That has always worked for me after numerous small and big block engines. Just put the bit in far enough to get the chuck to grab and tighten.

 

[MKTSC]

Are you just talking about those ports I'm going to plug up underneath the carb? I was wondering if there was a way to clean carbon out of the whole damn intake before installation...

 

[traintech55]

Are you just talking about those ports I'm going to plug up underneath the carb? I was wondering if there was a way to clean carbon out of the whole damn intake before installation...

Start from the side where the intake meets the heads. The port on the drivers side is real short. The passenger side is longer, but like I said I have never seen them clog all the way thru. This is also a good sign of bad valve seals on the engine the intake came off of.

 

[dart4forte]

I made this conversion on my 73 wagon. Plugged the EGR ports. However I went with the valley pan with the blocked crossover. I got an electric choke assembly through NAPA and installed it on my TQ. Motor didn't miss a beat

 

[saylor]

hey OK im a computer guy and NOT a mechanic. . . but . .

you trying to tell me those rusted out lookin holes in the base of the plenum is for an EGR ??

into the heat riser cavity ???

????

FWIW +1 on blocking the port with a felpro 1214 gasket or metal shims + RTV, but im down here in TX. we dont need any extra heat on the carb/intake.

 

[traintech55]

hey OK im a computer guy and NOT a mechanic. . . but . .

you trying to tell me those rusted out lookin holes in the base of the plenum is for an EGR ??

into the heat riser cavity ???

????

FWIW +1 on blocking the port with a felpro 1214 gasket or metal shims + RTV, but im down here in TX. we dont need any extra heat on the carb/intake.

Yes that is how all the auto manufacturers introduced E.G.R. into the intake manifold. And again yes, if you want to drive the vehicle in the cooler climates and not ruin your engine with raw gas washing past the rings you better have the heat riser passage in the intake manifold.

 

[MoPar Maniac]

Based on my experience with a 400 with the TQ I would get a Holley spread bore. That TQ is one thirsty mutha.
My 383 w 600 Holley got real good mileage. The 400 wouldnt pass a gas pump.

 

[traintech55]

Before anyone else chimes in about blocking off the heat riser passages, let me just ask this one question and lets see who is smart enough to answer. If the passages were not needed, why the hell did the engineers we all respect put them in, even on the Hemi.

 

[MKTSC]

Based on my experience with a 400 with the TQ I would get a Holley spread bore. That TQ is one thirsty mutha.
My 383 w 600 Holley got real good mileage. The 400 wouldnt pass a gas pump.

Well seeing as I'm getting a whopping 8mpg with my 2bbl, I'm not too terribly worried.

 

[MoPar Maniac]

Wow I got 10 with the 4bbl. Polara cop car and the 400/2 Monaco coud get 12-14.

 

[dart4forte]

Before anyone else chimes in about blocking off the heat riser passages, let me just ask this one question and lets see who is smart enough to answer. If the passages were not needed, why the hell did the engineers we all respect put them in, even on the Hemi.

The divorced (a.k.a. remote) choke closes due to a coiled bimetallic strip that rotates with temperature change. When the engine is cold, the coil acting through the choke connector rod, closes the choke. Contrary to popular belief unit does NOT open the choke (except for the 1937-1938 Delco unit, which never worked anyway, so the statement is still true). External heat to the divorced choke unit caused the coiled bimetallic strip to “relax” or “unwind” removing the closing tension to the choke plate, and allowing the choke plate to be opened by some other means. Early chokes were opened by a counterweight assembly on the choke arm, or by an offset on the choke plate to choke shaft connection, causing the choke plate to fall open when the tension was relaxed. Beginning in the late 1950’s, external choke pulloffs were used. The choke pulloff had a vacuum source attached, which pulled directly against the tension of the bimetallic strip. As the tension relaxed, the choke pulloff would open the choke plate.




Heat riser was for the choke to operate. Used heat to control the spring in the choke mechanism. If you run an electric choke it's not needed.