Ideas on Swapping a Weber Carburetor on a Subaru EA82 Engine
In this Writeup:
► Solving problems untold by the Manuals.
► Jetting for the EA82 to be used between Sea Level and ~ 6500 Feet (2000 Mts) Altitude.
► Proper PCV (Positive Crankcase Ventilation) Hoses Setup and installing an (optional) Oil Catch Can.
► A much better Adapter Plate than the one designed for the EA82.
► Intake manifold modifications (optional).
► What to do with ASV, EGR, etc...
► ...and Much More! Pay attention to the "Important Notes"
On early 2006 I Swapped a progressive Weber 32/36 Carburetor on my 1985 Subaru White Wagon (which isn't white anymore),, that swap job took much more things to do than what the Manual included with the kit, stated; so I'll explain everything needed to successfully do the Swap and I will add Photos, describing all the problems I faced and the ideas I had to solve them, here; Hoping that this writeup will Help you to Swap a Weber carburetor on a EA82 Subaru engine.
Many of the Ideas I'll explain here, might be aplicable to the older Subaru EA81 engine as well, almost everything except the adapter plate.
REMEMBER: Use this Ideas at your Own Risk!
First of All: the Redline-Weber K-731 Kit, which is designed to install a Weber carburetor on the Subaru EA82 carbureted Engines, comes with a Progressive Weber 32/36 Carb, an Air Filter Box plus its element, a Throttle Cable Bracket, some Gaskets and a two plate Adaptor, which consists on one Lower plate designed to be mounted directly to the intake manifold, and one upper plate, designed to be mounted over that first plate; this last one will have the studs which are intended to Hold the Weber Carb in place; and needs the Gaskets inbetween... Also it comes with a bag with different screws.
All those Weber carburetors that are Sold in USA comes with a sticker with a Statement that says something like: "For Racing -or Offroading- Purposes Only" due to Smog, pollution and other Legal Regulations that varies from State to State, so They're Not "Street Legal" on certain areas and that statement shall be placed on all brand new Weber Carbs, due to said Legal Regulations; so be sure that you are legally allowed to do this Swap on the Areal where you Live, prior to start.
There are many different Weber Carburetors' Designs on the market, however the two models used more often on Subaru Engines, are those who features two Barrels.
There are two variations of the two barrel design on Weber Carburetors, One design is known as the Progressive Models (Such as the 32/36 DEGV) and the other design is known as the Synchronous Models (Such as the 38/38 DGAS).
Each barrel has its own butterfly that opens / closes according to the Throttle position; if you want to be Sure which model do you have, just take a look at the Linkage that opens the butterflies between both Barrels, it is located behind the throttle plate: If Both Butterflies on both barrels, opens at the same time, always when the throttle position moves, it is a Synchronous Weber (Such like the 38/38 DGAS or a bigger numbered, like the 48, etc...); But if one barrel's butterfly starts to open only after the other one have already reached the half way open, then it is a Progressive Weber. (such like the popular 32/36 DEGV ).
The Synchronous Webers, such like the 38/38 DGAS are more used for Racing purposes due to the Higher Fuel usage (Both identical barrels works / opens at the Same Time, all the time), and thus means that if you use a Car with such kind of carb as daily driver, it will be a Gas guzzler, compared to the Progressive Webers, like the 32/36 like the one I Used, where you commute with only one barrel which is known as the Primary -Low- Stage (with a Smaller Jetting), usually; and the other barrel, which is known as the Secondary -High- Stage (with a Bigger Jetting) is used during deep accelerations only, so you have the Best Balance between Power and Fuel Consumption.
That been said, lets Begin to explain the Problems I Faced during the Swap Job, and How I Solved them.
~► First Problem: The Screws that Holds the Lower Plate.
The lower plate needs four screws to be Held properly in place, directly on the intake manifold; each screw has a cone shaped, flat top head, whose angle is approximately 60° and is designed to fit on the also cone-shaped openings of the Lower plate, letting the screws' Heads to be as Flat as the lower plate's Surface itself, and the inner angles holds that plate firmly in place. Those screws use hexagonal wrenches.
The Redline-Weber K-731 kit came with two different sets of screws to hold that first plate of the adaptor to the intake manifold, one set has the appropriate size and pitch of the Subaru's intake manifold's threads (1/4" ~ 6 mm), but the heads of those screws are very small, around the half size of the cone shaped openings at the first adaptor plate. The other set of Screws provided, are Bigger (5/16" ~ 8 mm) and their heads fills completely the cone shaped openings on the first adaptor plate; but their thread and pitch are bigger and will not fit on the intake manifold's threads.
It is impossible to bolt in a "safe" way, the lower plate to the intake Manifold using the thinner screws provided, but I bet that they included both sets, in order to let the Lazy mechanics to swap the carb fast and easy ... but those tiny screws will make the first plate to fit Loose, and develop vacuum leaks sooner or later.
So, some modifying job to the intake manifold is needed for sure: to re-thread the intake manifold's threads to the size of the bigger screws provided, in order to use them to hold the Lower plate properly, and firmly in place. That is what a true mechanic will do, to seek reliability.
I used the Bigger Diameter Screws, of course! (But continue reading: in further posts of this writeup I'll show you a more safe & Definitive way to solve this problem)
To make those Bigger diameter screws to fit, You'll need to Drill and tap new Bigger Threads to the intake manifold, but Be Careful when doing that: The intake manifold is also a coolant crossover, so you must take the proper measurements to avoid drilling onto a water passage. I Kindly Suggest you to remove the whole intake manifold from the Engine, prior to do the rethreading.
Here you can see how the Intake Manifold Originally was,
with the Craptachi Carb & Gaskets just Removed:
(Notice the Small threads on the Carb's Base)
So I took off the whole intake manifold to Drill the New Oversized Threads
From 6 mm (around 1/4") to about 8 mm (around 5/16")
Also I Sent the intake manifold to a Machine shop, to polish the flatness of the Carb's base:
Here, you can see how the Bigger Screws Now fits perfectly on the Subie's Intake:
Then, I Washed clean the intake manifold using Household Detergents, to remove any debris:
Important note: All the inbetween gaskets should be placed completely Smeared (the two faces) with Shellac, because shellac is Coolant / Oil \ Gasoline Resistant (more info on Shellac ~►Here) other gasket makers will fail in that place.
~► Second Problem: To Seal the (Now Unused) Water Passage for the Old Craptachi Carb.
If this procedure is not done right, the cooling system will spill coolant on the intake manifold, right to the carb's base opening, so be Careful!
My first solution was to place the Gasket completely smeared with Shellac over that water opening, and also I cut in half the tiny Hose which supplies coolant for that Passage, and cap closed both ends of said hose, using screws and clamps... That worked fine for five years, but you must consider that there is still a coolant flow inside the water crossover of the intake manifold; so there still will be coolant flowing on that Area, even without said hose.
You might use Cold Welding Compound such like the 4 minutes "JB Weld" to fill close that opening ... as I wrote, I ran my subie for years with only a Shellac smeared gasket and a removed hose without problems, but that setup was about to Fail after five years. Continue reading, in further posts of this writeup I will show you another Idea which is a definitive and permanent solution for this problem.
After placing the Gasket, smeared with Shellac on both sides,
inbetween the intake and the first plate, I bolted it there:
(Notice the Bigger Screws and how their Heads fills the Plate's openings)
Then, the Upper plate went over that first one,
Also with a gasket smeared with Shellac on both sides, inbetween:
And Then you can place the Weber Carburator.
~► Third Problem: Power Steering Equiped Models.
If your EA82 engined Subaru, has a Power Steering Pump, the Choke's Spring mechanism on the Weber Carb, will hit the Power Steering Pump's reservoir ... ... and even removing the Choke's Spring, the base for the said spring, impacts the bolt's head at the back of the power steering pump.
(the Choke spring was already Removed from the Weber Carburator)
Here at the Caribbean Tropics we don't need the choke too much, so my first solution was to Remove the Choke's Spring, but also I Needed to cut Half of the head from one of the Steering Pump's Rear Bolts, to prevent the Base for the choke's spring from hitting the power steering's back bolt. ... Another Solution is to Completely Remove the Choke's Spring Base from the Carb and its Butterflies (choke plates), so you'll not need to cut anything. Continue reading, because in further posts of this writeup I'll show you yet another and better Solution I found, later.
Important Note: I did installed on the Weber Carb, the throttle's Cable Plate Taken From the old Craptachi carb, plus the part of it that works with the Air Conditioner Accelerator Actuator, which with a simple twist on its metal plate (due to the new carb's different angle) I managed to made it work good.
So the Intake Manifold + Adaptor Plates + Weber Carb ended looking in this Way:
(Yes: Those are my dirty Hands)
Once installed, the EA82 Engine started at the Very First Try and Purred like a Kitten...
a Boxer Kitten! ... ... you know.
The Weber carb reveals somehow the Hiding potencial of the engine, and the Boxer Rumble Sound of the Carburated EA82's at its Best! ... While lets you Clean the crowded engine bay, removing lots of unused smog stuff. It is a Win-Win Deal for sure.
I Noticed a Huge Improvement inmediately! ... Summarized in a quicker Engine Response and Faster Acceleration, smoother Idle and a really noticeable Better Low end torque.
Fuel Consumption remains close to the Stock Specs... (if you drive carefully) ...but the Weber swap could make you to want to keep the gas pedal floored ... ... in that case, fuel consumption will increase for sure
Edited by Loyale 2.7 Turbo, 30 September 2015 - 12:36 PM.