Many of these modifications would also apply to the VW 1.7 engines used in Mopar vehicles from '78 to 82.
You can still get high performance parts for the 1.7, just look for Volkswagon GTIs & Corrados in the junkyard.

Round Filters
Through extensive research I have discovered that K&N sells not one but four different round (oval) air-cleaner assemblies for our carbs.

Part Number	Length	Width	Height
56-1010	9"	5½"	1.75"
56-1020	9	5½	3½
56-1025	7	4½	1.75
56-1027	7	4½	3½

K&N says only 56-1025 & 56-1027 will clear the feedback solenoid on feedback carbs.
The 3½" tall models probably won't fit without cutting a hole in the hood, the 9" long models won't fit without notching the firewall.
K&N also sells a 2½" plenum adaptor perfect for ram-air under p/n: 85-8921, it's designed for Weber DGV carbs but will probably fit non-feedback 5200s as well.

I have 56-1025 on my car and it won't clear the idle-solenoid without stacking a few gaskets under it. However, with the gaskets the air-cleaner studs aren't long enough to hold the filter down so you have to use or make extensions. The air-filter studs on these cars are usually the standard 1/4"x20 thread pattern.
Other then being able to hear the air-intake I haven't seen any performance gains using one of these on the street. Maybe it would show up if you cut a hole in the hood (my car has a header so the underhood air temp is fairly high).

Some chevy vegas and ford pintos use the same carb and have an "old-fashioned" round air filter too. I believe you have to notch the filter in one spot to clear the feedback solenoid and possibly cut out part of the firewall. Lots of foreign cars also use carbs with the oval mounting pattern.
Holley used to make a high performance round air cleaner assembly for our carbs but they don't sell it anymore (p/n: 120-206)

Spark Computer Cooling
Mopar says the spark advance computer uses incoming air to cool it's transistors and will burn out if the air intake hose is removed from it. If you're using a round filter or ram-air setup you won't have this hose hooked up anymore.

A power supply fan from a "mini-tower" PC case power supply works well to pull air through the computer.
Install the fan using a wire and a hose clamp as in the picture below.
The clamp will hold the wire down which will in turn hold the fan up against the air inlet. Make sure the fan is hooked up to a voltage source that is active only when the car is on (You can get switched 12VDC off of the "diagnostic" connector above the computer)

Intake Manifolds & Carbs
There are three different stock intake manifolds for the 2bbl cars. 1981-2 models have oval shaped ports and can only be used with '81-2 cylinder heads. 1983-4 models have the rectangular shaped ports and a removeable water box underneath. 1985-7 is the same as the '83-4 except the water box is cast into the manifold and not removeable.

Mopar Performance may still sell a high performance intake manifold for the 2.2s. It looks the same as a stock one except it has special "stuff" inside it for better fuel distribution. I have never seen one of these up close.

They had a dual carb intake manifold that would work with the factory Holley carbs (see the picture at the top of this page)
and even had a mini B&M supercharger (P4349478) that came with it's own special intake manifold & crank pulley.
See one in the picture below and check out the cast aluminum valve cover they used to sell that had the "TURBO" lettering ground off for installation on carbureted engines.

Their Weber dual carb conversion kits (P4349649 -carb & P4349566 -manifold) were supposed to give 15% more power.
You can still get these kits if you look around hard enough and want to spend around $800.
I managed to pick up a set of manifolds from eBay but do not have plans to install them yet.

The unit in the picture above has the dual weber kit along with the rare "direct connection" valve cover and a unique cam mounted distributor from a 440 V8 (using only half the plug wires)

Regular Weber "downdraft" carbs have the same bolt pattern as the stock carb so they're a direct fit. The throttle linkage will be different though. Mopar Performance used to sell one under p/n P4349300
I recently installed a Weber carb on my Duster and it isn't anything too special. Still a great alternative to the stock computer controlled Holley.

They also had an adapter plate that would let you use a regular 2 barrel Holley on the stock intake manifold (p/n: P4349665)
A Rochester 2GC carb has a similar bolt pattern so a Rochester to Holley 2bbl adaptor should work if you rework the mounting holes on the Rochester side.

Click Here for more info & modifications that can be done to the stock carb itself

Nitrous Oxide Systems has a Nitrous system designed for the stock Holley carb.
Chrysler originally sold it in their Direct Connection program as p/n: P4286598, but you can still buy the kit directly from NOS as p/n: 05011.  It comes with a special carb plate that's designed to spray a mixture of both fuel and nitrous into the intake when the button is pushed.  The only drawback to it is that it costs $548.53 (direct from NOS).
They sell the undercarb injector plate by itself (p/n 12942) for $123.53
Their systems for the the turbos can be found under p/n: 05208
It's a "fogger" system that and will work on most 4 & 6cyl turbo engines.

I'm sure you could make your own nitrous kit out of a CO2 bottle & some plumbing, the only trouble would be getting the bottle filled

The picture to the right shows an experimental Direct Connection Hilborn fuel injected engine from 1985. I don't know if any other similar kits were ever made but it looks cool...

Gaskets & Spacers
Mopar Performance used to say to stack 3 gaskets at the air cleaner to carb junction for better air flow. The older engines, with the fuel vapor separator built-into the fuel filter, have really thick rubber gaskets between the carb & air-box. You won't be able to get more then 2 of these gaskets on without adding longer air-cleaner studs
You can get a decent sized air-filter to carb spacer off a chevy chevette with the 1.6l motor.

Raising the carb is supposed to increase the "ram effect" of air going through the manifold, and keep fuel from sticking to the manifold floor, thus increasing torque. I haven't messed with that yet so I can't say for sure.
Some Chevy & Ford versions of the 5220 carbs come with a 1/4" spacer that goes directly under the carb. One of these will barely fit under a 2.2s carb without replacing the studs in the isolator/adpator. If you have an automatic transmission you might also have to re-adjust the kickdown cable after installing the spacer..

You can add a second bakelite gasket under the stock isolator/adaptor to lift up the carb around a quarter inch. The Mopar part number for these is 4179302. This raises both the carb and throttle cable bracket at the same time so no re-adjustment would be necessesary.

I have seen three different types of intake/exhaust gaskets for these engines. p/n 5214650 is the old copper gasket that can't be reused. I don't think you can even get it anymore. The new "composition" type gasket (p/n 04105745) is thicker then the copper one and can cause problems on some of the carb'd cars because the extra thickness causes the intake manifold bolts not to thread in as far. It is the same as the regular FelPro gasket. The third type of gasket I found came with my MP header. It is a paper (maybe asbestos?) gasket with no part number on it which I haven't ever used.

Intake Heater line re-routing
It's been said that disconnecting the water lines running under the intake will give you a cooler intake charge and thus more horsepower. I did this on my car and I don't know if it went any faster but it did take longer to warm-up when it's cold out (but I don't drive that car in the winter so I don't care).
Hot air gives better gas mileage, cold air gives a little more power.
You can simply connect the connector at the heater core (that used to go to the intake manifold) to the connector at the bottom of the water box.The heater core has a 5/8" connector and the water box has a 1/2" connector, so you have to use a reducer.

Misc. Air Intake Mods
You should probably take a 5/16 fuel filter and put it inline between the charcoal canister (evaporative emissions canister) and the carb. This will keep chunks of charcoal from the canister out of your carb.
When I opened up my carb for the first time there was a whole bunch of dirt in the float bowl.
Don't just remove the canister, all you'll do is hurt your fuel economy. It simply takes fuel vapor, filters it, and puts it back into the intake. It has no effect on horsepower whatsoever.

Also, check the rubber hoses that are in-between the fuel filter & carb. Stick a golf tee inside the hose and remove it. If the end of the golf tee has black dirt on it, the hoses are probably deteriorating on the inside and should be replaced to keep the black gunk from getting inside the carb. This is why the Chevy & Ford versions of the Holley 5200 have fuel-filters that screw directly into the carb.

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