Where does the circled hole go to, I assume to the cylinder, and vacuumed?
I'm looking to block it, but I don't want to remove it for machining. I guess I can't tap it with it installed because of the shavings the would fall inside? Any ideas.
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1. EGR Port. 'Exhaust Gas Recirculation'.
2. A plate sits on top with a Vacuum Diaphragm that opens a closes a Valve that allows Exhaust Gases to Mix-In with, and Dilute and Heat the Fresh-AIR/FUEL Intake Charge.
3. Was suppose to Increase MPG and Reduce Actual Emissions?? And Speed-up 'Cold Morning' Warm-up.
4. You could Tap it with threads and the Chips would just fall into the Exhaust port and get Blown Out, into the Muffler.
5. What I Did....Go to NAPA and purchase a 3/8"- 1/2" 'Cup Plug'. They do exist and look like a Small 'Freeze Plug'.. Get One and Drive it in Solid with a Tight fitting Drift. DONE!! Make sure You Buy it in Steel or Brass, ALL Others Will MELT! I have long since UP-graded to an After Market Aluminum Intake.
6. You could also, cut-off a Length of Steel, Copper, Brass, ROD, and Drive THAT In! NOT Lead! It will Disappear!
7. FYI....The Factory EGR Plates are the First thing to Corrode, Seize and Fail. If it was Your aim to Replace it...a New Plate can be Near Impossible to Locate.
MJ
Thanks Marlin, so this hole doesn't need to be sealed off as in vacuum, but just so things don't fall in there?
1. Guess I Wasn't very Clear, That Passageway is Connected to a Exhaust Port.
2. HOT Exhaust Gases WILL Come Shooting Out Of There!
3. You DO NOT Want the Bottom of the Carburetor to Be Constantly BLASTED with Extremely HOT Gases!
4. So PLUG IT! Or, use Intake Gaskets with the Port Closed-Off.
5. The adjacent Larger Hole with the Two smaller Holes, is for the Choke Heater COIL. Or, It too, must be Blocked Off. There are Parts for this.
6. Any Vacuum...went to the 'Vacuum DIAPHRAM MOTER', this controlled the EGR Valve that Had been Mounted on That EGR PLATE, mentioned earlier, and is now missing in your photo. In you case you don't need to worry about a Vacuum Source. Only Leaks to the Carb Base! Carry-On!
MJ
I got it, thanks very much!
Everyone complains what a travesty it was that the smog era robbed the American V8 engines of their performance; carburetor tuning was the major factor in the reduction of horsepower. Ford's '73 and '74 4300D carburetors rob the engine of about 90 horsepower compared to a carburetor in a "pre-1968" state of tune. The fuel bowl is also too small, and is credited for causing a stumble when accelerating out of corners. The booster venturis are quite crude as well compared to the annular booster venturis employed in Ford's earlier 4100 series carburetors.
I find it hard to believe that anyone would want to utilize a 4300 series carburetor. Its like driving the car with 2 plug wires removed. Placing originality above "functionality" is not my bag, especially since a carburetor cannot be seen when the air cleaner assembly is installed. Nobody will notice what carburetor the engine is equipped with … but the driver WILL notice the car's improved acceleration (0 to 60 will drop from 8 seconds to 6 seconds). Thus I am an advocate for replacing 4300D carburetors with better carburetors.
Ray I mention this not to change your mind necessarily, but to simply make sure you (and others) are aware of this situation.
The hole you indicated provides exhaust gas to heat the carburetor and supply exhaust gas to the EGR valve. To disable it thread the hole and screw-in an Allen head type lock screw.
Even with that small hole blocked exhaust heat is still supplied to the cross-over passage below the manifold. You should use the turkey pan type intake manifold gasket, because it provides a heat shield which prevents the motor oil from splashing against the "hot" exhaust heat passage which runs beneath the intake manifold.
If you wish to use the 4300D carburetor, but you don't plan to use EGR, then perhaps consider installing the 1972 intake manifold (D1ZE casting number). It has the spread bore configuration but lacks the big EGR passage on the right hand side.
George, I did replace the 4300 with a Holley 600, not because of the poor performance, but because of the failed attempts to stop the leaking between the top and bottom bowl, I didn't want to replace the manifold at this time. I tapped the hole, 1/2 13 thread, and used the allen style set screw like you listed. Worked well.
It pains me to move away from originality, but the car has to be able to be driven reliably.
