BRN2RUN
Active Member
There's more about it in my garage, so i'll try to limit this (mostly) to the ongoing build. I wanted this car as an FI car to mess around with and improve upon, and hopefully to de-mystify them a bit, in case anyone is thinking about doing a swap. Originally, I was thinking about doing an M90 conversion on my Mustang, but figured that it would probably just be easier overall, if I had got a 'Bird in good condition to work on, and continue on with my N/A 3.8 Mustang build. Mostly this is just to geek out with some people to kind of expand on something that's often discussed or considered on a Mustang setup, but abandoned due to the split port/ single port conversion hassles. Whether someone is doing an engine swap, or can custom fab up some sort of side mounted M90, it's some sort of small victory in keeping it Ford power, but a more unique type of build than most may expect to see at a car show.
The great thing about the SC engines is that the crank is forged, so are the rods, and the pistons are a reinforced hyper alloy. But more often than not, the weak point in the system is the head gaskets......too much heat and stress on them has led to many an SC sent to the wrecker, so part of my intention here is to have a smart, daily driver build, that minimizes heat and maximizes power on an affordable budget--some DIY stuff, a little MacGuyver thrown in there for good measure, too.
I've done a few modifications to mine last year before putting it in storage--Ken Wagner double intercooler, K&N panel air filter, heavy duty supercharger belt tensioner springs, air silencer removed, new plug wires, spark plug change (difficult on these cars), but the best modifications (many of them) are coming soon.
Why install a 94/95 supercharger and injectors? It is a more efficient, revised Eaton M90 that in conjunction with the 36 lb injectors (as opposed to 30 lb injectors on 89-93 SC's) delivers 20 hp/ 20 ft lbs more of torque. The rotors are a more efficient design, that create less heat and less stress on the engine, with a slightly less overdriven supercharger pulley (for example, you can put on an 89-93 pulley on the 94/95 supercharger and get a bit more overdrive). The 94/95 blowers are a little more difficult to find, but if you can find them, it's much more worthwhile to put them on your build.
Ported and polished/ modded stuff that I did in the last little while:
Ported/ polished 94/95 Eaton M90 as I had received it:
Draining the fluid (it is true what people say--it smells horrible):
Prying the rotor pack away from the case:
The rotors! They are in great condition:
The case as I received it after removing the rotor pack:
The case and ported outlet as I had received it--a pretty good job:
Cutting off the bolt bosses:
Supercharger case ported and polished (slightly more of a "smile" look):
S-port in the supercharger, bevelled/ rounded edges to smooth airflow:
The outlet from the outside, with bevelled/ rounded edges to smooth airflow:
In comparison, here is a Magnum Powers outlet size (left), compared to a stock outlet size (right)--mine is fairly comparable to the MP dimensions, though mine are rounded (don't know if that would increase power or not, but I wanted sharp edges to be as minimized/ eliminated as possible):
Here's a pic of the step inside the mouth of the plenum at the 75mm Professional Products throttle body that i'd bought, to show what type of sharp edged step exists when it's not port matched to the larger throttle body:
This was the ported plenum as I received it:
After smoothing/ easing the transition of most of the throttle body port in the plenum, I used some Prussian Blue and put the throttle body on to figure out exactly where the idle bypass area had needed smoothing. Not sure if this would add any power, but figured that there was no point to having a stepped area preventing idle air flow. Could be my OCD kicking in, I dunno
:
The finished plenum port to the throttle body, polished to a 400 grit and then using metal polishing paste--the weak link in the plenum is still the vacuum lines/ egr port/ etc. Even if you block those things off, you still have all those weird entrance shapes in there:
The throttle body matching up to the plenum (it is true about what people say of the stock plenum bottlenecking down to 68mm or so.....though removing the step at the TB port and polishing it should increase flow and velocity through the plenum). It's a bell-like shape, with the mouth of the plenum having a bit of a venturi, which, if you think of velocity stacks, should draw in a good amount of air still, but should keep velocity high in the plenum. Notice that the throttle body is half shafted, and the sharp screw ends are ground down flush with the shaft (I used some Loctite to prevent the screws from loosening):
Some in depth plenum pics.
Getting further into the plenum with a flexible drill extention:
Using a piece of wood as a lever to act as an additional way to direct the grinding bit, to get at areas that would otherwise be impossible to get at:
I had to put my hand in the other end of the plenum to stabilize it for another area, and there was no way to do this visually to find out where I was getting at......reminds me a lot of doing the spark plugs on the driver's side on these cars--you have to MacGuyver it in from below and feel around for the spark plug hole. I had to go by the grinding sound, comparing it to when the casting marks were removed on the rest of the plenum. Didn't take a huge amount of time, but it did take patience:
Smaller flapper wheel used to get at yet another area (went through the air bypass valve port):
This isn't the finished picture of this edge, but I had rounded this off to provide a slightly less torturous angle for air to flow on the short side of the plenum.
Plenum opening into supercharger. I am aware of how little metal there is here to seal on the bottom edge--it's possible that there could be vacuum leaks here, but i'm going to seal it the best that I can. If there's problems, I could just redo another plenum, no problem. I wanted to have as much area opening into the supercharger as possible.
View of the plenum connection to the case--the opening has a venturi/ bell type of rounded edge, which should help the supercharger draw air in through the case:
I took a look at the air bypass valve area, and perhaps there's no power to be gained here, as the valve closes at boost. Could be more of my OCD, but one would think that at cruise speeds, the throttle would be more efficient/ responsive. This is essentially a secondary throttle blade, and a very small one, at that. It may have been a design from Ford, so that the car wasn't too jumpy and uncivil. Look at the huge step from the plenum to where it meets the bypass valve port throat area. Would this ease a transition between n/a power and boost? I don't know. Sounds like a cool theory, though:
Here's the stock area (though with the blade removed). Lots of sharp edges:
This is with the step ground down and the throat transition area eased:
Here's with the air bypass blade, assembled and half shafted (with the screws ground down, and with Loctite on the threads), to increase the available airflow. The shadow makes the ground down step look like it's still there; in reality, it's yet another one of those bell shaped venturi shapes:
Here's a picture from inside the plenum, in how the opening is smoothed and rounded into the air bypass port, before the throat area:
Picture of the ported supercharger inlet as I had received it, as the rotors see it (the blue dye is prussian blue, to gauge the amount of material contacting the surface between the plenum and supercharger. I'd figured that a better way to match it up was just to take the case and attach the plenum):
Another picture--a fairly rough porting job as I received it:
My revised version, again with a 400 grit finish and then metal polishing paste:
A closer look:
The great thing about the SC engines is that the crank is forged, so are the rods, and the pistons are a reinforced hyper alloy. But more often than not, the weak point in the system is the head gaskets......too much heat and stress on them has led to many an SC sent to the wrecker, so part of my intention here is to have a smart, daily driver build, that minimizes heat and maximizes power on an affordable budget--some DIY stuff, a little MacGuyver thrown in there for good measure, too.
I've done a few modifications to mine last year before putting it in storage--Ken Wagner double intercooler, K&N panel air filter, heavy duty supercharger belt tensioner springs, air silencer removed, new plug wires, spark plug change (difficult on these cars), but the best modifications (many of them) are coming soon.
Why install a 94/95 supercharger and injectors? It is a more efficient, revised Eaton M90 that in conjunction with the 36 lb injectors (as opposed to 30 lb injectors on 89-93 SC's) delivers 20 hp/ 20 ft lbs more of torque. The rotors are a more efficient design, that create less heat and less stress on the engine, with a slightly less overdriven supercharger pulley (for example, you can put on an 89-93 pulley on the 94/95 supercharger and get a bit more overdrive). The 94/95 blowers are a little more difficult to find, but if you can find them, it's much more worthwhile to put them on your build.
Ported and polished/ modded stuff that I did in the last little while:
Ported/ polished 94/95 Eaton M90 as I had received it:
Draining the fluid (it is true what people say--it smells horrible):
Prying the rotor pack away from the case:
The rotors! They are in great condition:
The case as I received it after removing the rotor pack:
The case and ported outlet as I had received it--a pretty good job:
Cutting off the bolt bosses:
Supercharger case ported and polished (slightly more of a "smile" look):
S-port in the supercharger, bevelled/ rounded edges to smooth airflow:
The outlet from the outside, with bevelled/ rounded edges to smooth airflow:
In comparison, here is a Magnum Powers outlet size (left), compared to a stock outlet size (right)--mine is fairly comparable to the MP dimensions, though mine are rounded (don't know if that would increase power or not, but I wanted sharp edges to be as minimized/ eliminated as possible):

Here's a pic of the step inside the mouth of the plenum at the 75mm Professional Products throttle body that i'd bought, to show what type of sharp edged step exists when it's not port matched to the larger throttle body:
This was the ported plenum as I received it:
After smoothing/ easing the transition of most of the throttle body port in the plenum, I used some Prussian Blue and put the throttle body on to figure out exactly where the idle bypass area had needed smoothing. Not sure if this would add any power, but figured that there was no point to having a stepped area preventing idle air flow. Could be my OCD kicking in, I dunno

The finished plenum port to the throttle body, polished to a 400 grit and then using metal polishing paste--the weak link in the plenum is still the vacuum lines/ egr port/ etc. Even if you block those things off, you still have all those weird entrance shapes in there:
The throttle body matching up to the plenum (it is true about what people say of the stock plenum bottlenecking down to 68mm or so.....though removing the step at the TB port and polishing it should increase flow and velocity through the plenum). It's a bell-like shape, with the mouth of the plenum having a bit of a venturi, which, if you think of velocity stacks, should draw in a good amount of air still, but should keep velocity high in the plenum. Notice that the throttle body is half shafted, and the sharp screw ends are ground down flush with the shaft (I used some Loctite to prevent the screws from loosening):
Some in depth plenum pics.
Getting further into the plenum with a flexible drill extention:
Using a piece of wood as a lever to act as an additional way to direct the grinding bit, to get at areas that would otherwise be impossible to get at:
I had to put my hand in the other end of the plenum to stabilize it for another area, and there was no way to do this visually to find out where I was getting at......reminds me a lot of doing the spark plugs on the driver's side on these cars--you have to MacGuyver it in from below and feel around for the spark plug hole. I had to go by the grinding sound, comparing it to when the casting marks were removed on the rest of the plenum. Didn't take a huge amount of time, but it did take patience:
Smaller flapper wheel used to get at yet another area (went through the air bypass valve port):
This isn't the finished picture of this edge, but I had rounded this off to provide a slightly less torturous angle for air to flow on the short side of the plenum.
Plenum opening into supercharger. I am aware of how little metal there is here to seal on the bottom edge--it's possible that there could be vacuum leaks here, but i'm going to seal it the best that I can. If there's problems, I could just redo another plenum, no problem. I wanted to have as much area opening into the supercharger as possible.
View of the plenum connection to the case--the opening has a venturi/ bell type of rounded edge, which should help the supercharger draw air in through the case:
I took a look at the air bypass valve area, and perhaps there's no power to be gained here, as the valve closes at boost. Could be more of my OCD, but one would think that at cruise speeds, the throttle would be more efficient/ responsive. This is essentially a secondary throttle blade, and a very small one, at that. It may have been a design from Ford, so that the car wasn't too jumpy and uncivil. Look at the huge step from the plenum to where it meets the bypass valve port throat area. Would this ease a transition between n/a power and boost? I don't know. Sounds like a cool theory, though:
Here's the stock area (though with the blade removed). Lots of sharp edges:
This is with the step ground down and the throat transition area eased:
Here's with the air bypass blade, assembled and half shafted (with the screws ground down, and with Loctite on the threads), to increase the available airflow. The shadow makes the ground down step look like it's still there; in reality, it's yet another one of those bell shaped venturi shapes:
Here's a picture from inside the plenum, in how the opening is smoothed and rounded into the air bypass port, before the throat area:
Picture of the ported supercharger inlet as I had received it, as the rotors see it (the blue dye is prussian blue, to gauge the amount of material contacting the surface between the plenum and supercharger. I'd figured that a better way to match it up was just to take the case and attach the plenum):
Another picture--a fairly rough porting job as I received it:
My revised version, again with a 400 grit finish and then metal polishing paste:
A closer look: