T-Bird SC 3.8 build


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:


Sideshow Bob

Active Member
Real nice job on the porting. I did the same thing to the Eaton on my 2003 lightning. I used JB weld on the silencers to close them up. I don't no if it will work on the M90 but in the photo the Magnum Powers don't have them. It can give about a 1/2 pound of boost on a Eaton. But it will be a lot louder. :)


Active Member
Thanks! Were you afraid of the JB Weld breaking off? I was thinking of welding the silencers shut, but had decided against it.


Very good info! Ive not had the supercharger on my 89 SC apart like that so it was very interesting!


Active Member
I'd bought a return plenum off of Bill at SC Performance. I could have just re-used mine, but I want to have everything ready and done to install the car instead of taking a while longer to put it on after porting/ polishing. Plus, any snags with the work/ parts and I can still drive the car.

Used return plenum as I had received it--this is the inlet. I'm guessing that this was from a somewhat high mileage car, based on the overall condition of it on the outside and inside. The casting was the worst in here out of everything that I've ported so far.....stampings, uneven metal distribution, plus that ridge that you can see almost an inch or so into the plenum. Based on the oil and gunk that has built up in here, there's a pretty good case for an air/ oil separator, just to keep the blowby and oil and gunk out of the engine:

The same one, but ported and polished:

Boost bypass throat area:

Boost bypass throat area ported and polished. There's a somewhat sharp edge that it has to maneuver as it transitions into the larger plenum area, and I had rounded this edge a fair bit. No idea if this will create any power (especially as it is an N/A thing for when the bypass is open), but i'm hoping that small improvements like this may improve the N/A power a small bit and may smooth the transition from N/A to boost and from low vacuum to boost:

8" intercooler fan for the custom double intercooler. I had wired this up myself to always be on with 12V switched ignition. I may eventually put it on a toggle switch, but it's good enough for now. After "spirited" drives on the highway, I felt the upper IC tube and IC and both were barely warm (ie: it would take a little while to melt butter). The lower IC tube wasn't even warm at all, though this was on a chillier spring day and the real test is in the heat soaked months of the summer. I'm hoping that it doesn't rise much above ambient, because the difference in the car last year from spring to summer back to fall, you can tell that the computer pulls a bunch of timing to avoid detonation.

The fan makes a huge difference in lowering air charge temperatures, because it moves a ton of air. It's also wired to draw air and pull it out/ through the IC, and oddly enough, the stream of air is also fairly close to the lower IC tubing and not that far away from the driver's side manifold which may further lower underhood temps:


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Active Member
I decided to port and polish the supercharger top hat, that connects to the intercooler tubing (the tubing and intercooler will be the next to be P&P'd). Most guys buy the Magnum Powers raised top hat, but there's too many people out there saying that they've dynoed their cars with the setup and it didn't improve anything--no psi drop, no power gains. I got to thinking that despite the MP raised top with a much better exit/ throat area into the intercooler tubing, that the idea of flow versus velocity may come into the picture--where a bigger tube/ port size may lose some pressure.

After doing mostly bolt on modifications and various cooling mods (removing the front A/C condenser to get more air into the radiator and double intercooler; installation of an intercooler fan), there was some airflow modifications (K&N panel filter, Dynomax Ultraflow duals, catalytic converter delete, air silencer delete) that dropped the stock 12 psi to just a little over 10 psi (10.25-10.5 on the boost gauge). I was pleased to see that the ported/ polished top hat dropped the psi on the boost gauge to 9.25 to 9.5. It definetely did not scrape the 10 psi mark. The result with the lowered psi is that the low end torque may have been dropped a little bit (still roasts the rear tires though for a burnout of a few feet), but the top end feels improved. The lowered psi should make it much safer to run a 10 percent overdrive pulley, which adds about 3 psi.

Top hat exit stock--not too bad, but the inner tube part doesn't match the outer collar connector part, a step which would cause some turbulence going into the connection at the top IC tube:


Ported and polished--no trace of any inner tube with the collar connector transition or step:


The inside of the stock top hat--the two round casting bumps in the middle can't be good for flow, nor can that nasty assed weld. The fins are pretty good in stock form:


Ported and polished:


The inside mouth of the exit to the intercooler in stock form (the roughness of the welds show here a little more on this angle).


Ported and polished version--I speculate that if one were to do a real quick, crude version of this (all in all, this was about 10 1/2 hours) you could get away with a few hours' work in just grinding down the two round casting flaws, as well as the welds, and this throat area:


6 Shooter

Well-Known Member
Think the reduced boost may be the result of less restriction in the system due to your amazing porting. That is what showed up on a lot of porting on the old ProCharger system and upper/lower intake.

Phil II

Cone Destroyer
I agree that your porting and polishing is amazing. I don't think that it makes it any safer to run an over-drive pulley.

Generally speaking your compressor is working less to move nearly the same amount of air. Meaning that engine is making the same or more power. Stepping up the pulley will likely push the motor closer to its mechanical limits.

If you're concern is pre-detonation then I suppose the above is for nought.


Active Member
I agree that your porting and polishing is amazing. I don't think that it makes it any safer to run an over-drive pulley.

Generally speaking your compressor is working less to move nearly the same amount of air. Meaning that engine is making the same or more power. Stepping up the pulley will likely push the motor closer to its mechanical limits.

If you're concern is pre-detonation then I suppose the above is for nought.

I do run 94 octane, just in case. 91/92 is recommended by Ford, but of course, when one runs a smaller pulley, there are always risks. :) The intercooler upgrades keep the boost heat way down.....granted, it's spring right now and the temps are cooler than the heat soaked months of the summer, but right now, the upper intercooler tube/ intercooler is barely warm, and the lower intercooler tube is cool to the touch after the car gets up to operating temps and even after a spirited highway run. Keeping the intercooler fan all the time really helps--it moves a lot of air.
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Time for a little improvement on the dull grey colour of the stock supercharger top and upper IC tube. The IC tube, surprisingly, took about 45 minutes, as I had just used a flapper wheel to sand off the paint and make it a brushed aluminum finish. The supercharger top, originally I wasn't going to do, but the paint was flaking off, so I had decided to take a wire wheel and give it a brushed aluminum finish. A very small grinding bit (1/16" or so of a head) was used to detail around the lettering and remove the last bits of the original paint. The brushed aluminum finish looks good, I thought , but the raised 3.8 lettering and the raised stripes were looking too plain, so i'd painted those, as well. Fully finishing the top took longer than I thought, because of all the curved surfaces and around the lettering and was starting to fall into the "gee, i'd rather pay someone to do this" category, heh heh.



Active Member
I'd spent the other portion of last Saturday doing the inside of the upper intercooler tube, and the custom double intercooler. Even on the SC forums, the number of people that have done this is few and far between, but this is the first modification that really feels like it added a lot of upper end, rather than adding low end torque. These engines make a lot of low end torque, but by 4000 rpm, they really drop off and in between 4000-5000 rpm, it feels like the car has lost a gear or two. From 4000-5000 rpm, it still wants to pull hard now, and more specifically, between 30-70 mph (and beyond!), it just doesn't let up anymore.

Another upside to removing the paint from the supercharger top and giving the upper IC tube a brushed aluminum finish (also removing the paint), is that i'm wondering if the part from the supercharger to the intercooler isn't dissipating more heat into the engine bay instead of being trapped in the tubing/ intercooler. At any rate, the car is approaching the "hold on for dear life" feel in the upper revs that it's always had in the lower rpms, and the throttle is more responsive.

The upper doesn't appear to be much of a restriction--there's no sharp bend, although there are several casting marks in it (kind of looks like little sewer covers), and the rectangular part where the tube cuts in to make room for other parts in the engine bay is somewhat jagged. There's probably a 2-3 mm enlargement in the whole tube, and the mouths/ connecting areas have been enlarged by a few mm, as well.

Inside of the intercooler tubing from the supercharger top, stock:

Ported and polished. Note that the casting line in the middle part of the tube is fairly difficult to remove to be flush with the surrounding metal, plus I didn't want to weaken the metal too much:

Stock upper IC exit into intercooler:

Ported and polished:

On the ported/ polished versions, I had used a flexible drill extention to get into it with a flapper wheel, and had sanded it to a 400 grit finished and used metal polishing paste as far as I could get in with my fingers.

Double intercooler inlet, stock. Not too bad, but it's the super sharp edges on the inner opening part of the inlet that would likely be a killer on airflow as they try to negotiate their way around the outer perimeter into the larger part of the intercooler

Ported and polished:

I forgot to take a picture of the stock DIC outlet, but here's the ported/ polished version. Note the weld on the inside--not much can really be done about it (and I didn't want to weaken the welds too much), I had knocked down a bit of it and gave it a somewhat smoother surface, but the overall area is large and the outlet throat area is most likely more important on flow (especially with the same sharp inner edge on the opening into the throat. The connection area for the lower intake tube was massaged and opened up a little larger to match the intercooler tubing opening.



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These tires were done. They were on the car when I bought it last year and they were in dire need of replacement:


New Continental ContiExtreme DW (dry/ wet summer only) 225/55/16's. I wanted to keep the stock sleeper look of the car, plus the tires/ rims weigh the same as the factory (maybe a little less with the 55 height instead of the stock 60 height)


Well, you could say that with only a bolt on/ exhaust setup already on a mostly stock '89 engine, the throttle will require modulation to get a decent launch without tire spin, and perhaps dropped tire psi will help. More impressive is that this road had a slight incline to it. The cooling/ intercooler mods have definetely helped, and at this point, all of the modifications are just working with what's already there. Still 17 MPG-ish in town, and keeping that smooth, luxo-cruiser feel, so far.

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I'd put the 1994/1995 s-port and polished supercharger case/ plenum on the car today, along with a 10 percent overdrive pulley, and it being my first attempt at supercharger port/ polish work, I was a bit nervous to turn the key after i'd double checked all of the connections, bolts, hoses and other things. I fired the car up and it ran perfectly--no boost or vacuum leaks, and I took the car out on the highway and did a WOT run, and it ran great--and incredibly fast. The boost was higher than I thought it would be--15 psi, as i'd dropped the psi from the stock 12 to just under or around 9.75 psi with some exhaust improvements and intercooler piping improvements. It may even be more than 15, as the gauge only goes up to that level, but the 10 percent od pulley usually gains about 3 psi, so it was at least 2 psi more than i'd thought there would be.

The most noticeable difference is how much louder the supercharger is now, and even at part throttle. The underhood temps, temperature gauge read where their normal levels should be even after the WOT runs, and the temperature of the supercharger top/ upper IC weren't very hot, and the lower IC return tube was even cooler than that. Even with the added boost and air out of the supercharger, the engine doesn't seem to be anywhere near as strained as it was in stock form, as the 94/95 SC supercharger is a much better design (bigger inlet, coated rotors, etc)
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Update: i'm still a little hesitant to give it a full 0-100 or something run, but a 0-70 run, at least, nothing has blown apart. :) I say this because the weak link now is the stock 30 lb injectors and stock pump. I would do 'em, but alas, funds are short (I have 36 lb injectors, but won't have the $$ for a tune for a while. I'll probably get it dyno tuned). Most reputable sources say that the stock 30 lb-ers are good to 275 crank HP, and less safe to 300 crank HP, because the injectors start working at a less reliable 80 percent duty cycle (and beyoond) in that range. I'm not hearing any detonation, but you never know.

The car is at the "holy geezus, something is gonna break" stage, and it's about a 5.5 second 0-60, if I can get the traction modulated correctly off the line. For a nearly 4000 lb automatic car, that's a pretty good accomplishment, as the stock auto's are about 7.4-7.5 seconds from 0-60. It doesn't matter if it's in first, second or third gear, it spools up ridiculously fast and though it is still a bit slower in the upper rpm's than the lower ones, the drop off that was felt after the 1st gear in stock form after the torque curve goes down isn't much of a difference anymore, where it feels almost as fast when the torque peak hands off to the horsepower end of things. The boost gauge is burying the max psi on the gauge at 15 in short order, and I think that i'll get an aftermarket boost gauge that can read beyond that to see how much boost is actually being made.

I had bought a Professional Products 75mm throttle body last year from the same guy that i'd bought my late model blower off of. The PP throttle bodies are notorious for being hit and miss, and mine was a miss......i'd tuned the TPS to the right voltage at idle (.92-.96 or so), and it had a hanging idle that couldn't be solved (checked the IAC, adjusted the idle bypass screw, etc) and no luck. At full throttle, it didn't seem to make a difference, anyways--though i'd ported the opening of the plenum to 75mm, the stock plenum necks down to about 68mm, anyways.

Stock TB front:


Ported and polished version. Time to let that gold shine! The screws were also rounded off a bit, enough so that the sharp edges were mostly gone, but enough of the screw left that I could use a ratchet to get them off or on. I think that the TB is about a 60mm size or so, but if you look at the velocity stack type of mouth on it, it would keep the pressurized flow high through the TB:


See through view of the stock throttle body before modifications. The screws protrude quite a bit, but I give Ford credit: they half shafted the TB at the factory, so overall, it's still decent in factory form:


After modifications--the threaded area of the screws is gone, and the shaft is shaved down. I Loctited the screws:


Rear view of the stock TB, unmodified:


Stock TB, but ported/ polished:


Also, as the throttle body runs coolant through it, I disconnected the hoses and connected them with a tee connector with hose clamps. Most people seem to think that the coolant run through design is meant for cars in the winter so that the throttle body doesn't stick. Seems to make sense, and Ford discontinued this idea, anyways. I don't drive my car in the winter, and if the bypass helps keep the TB a little cooler because coolant isn't heating it up, that's good, too.


Active Member
I'd installed a 76mm C&L mass air flow that i'd picked up in a package deal off of a guy that sold me my 94/95 SC blower, mainly because it was used, cheap, and available. I just couldn't get the thing to run right, at all. The car idled terribly; bucked, surged, etc. It's the proper sampling tube (gold/ yellow) for 30 lb injectors. I drove it a couple of blocks and decided that I was going to take it off. It's not worth the hassle of trying to clock it or trying to straighten out the air or whatever. The C&L's when calibrated properly, I might assume work awesome and might deliver good power, but it's just that the threat of going lean at 15+ psi isn't something I want to happen. C&L says that with the air silencer removed, and K&N filter panel and stock airbox, that it should work well, and that things like cone filters mess up the calibration.

In fairness, I did drill holes in the bottom of my airbox--so there is the chance that it's drawing in way more air or maybe more turbulent than C&L intends it to be, but some guys just haven't got their to run right on Fox body 5.0's or SC's, without modifications. The stock intake system is somewhat restrictive (partially as an attempt to reduce blower noise for those that want it to be fast, but quiet), but if the gains incurred by reducing those restrictions have to be precisely dialed in on a MAF, you'd have to have a wideband O2 gauge or be on a dyno to really adjust things anyway, which would defeat the purpose of a bolt on modification.

This is a great tutorial (cnlperformance.com) but there's too many ifs and variables in there...for me, at least.
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6 Shooter

Well-Known Member
Do you have any way to data log the car as it currently sits? If you do not have an XCal 2 or 3, maybe there is someone in your area who does have one that you could borrow for a half day. If yes, reply back as there will be some settings that you may have to have SCT tech assistance help you match up. You will also need a laptop with a printer cable. It's also a pain to learn new software settings, but I posted a list of data elements to data log when creating a config.sys file for the laptop. Pretty cool once it is all setup and the data spits out in spreadsheet form.

From your explanation, the MAF is either not wired correctly or the calibration is pretty far off, for starters.


Active Member
This is an OBD1 setup, so it's more difficult to do. Oh how I wish there was SCT assistance. :) Compared to today's tuning options, the tuning capability is like driving a covered wagon. Then you have the AOD, with no electronic tuning capability and only shift kits (as far as I know).

There's a Moates Quarterhorse and Binary Editor that you can tune and adjust things in real time, so when cash flow dictates it, that's what i'm getting next.


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The original gauges have a decent, understated look, but could use a bit of color to liven things up:


Got some vinyl overlays/ inserts from Whitefacegauges.net, and they look fantastic, I think. Especially considering that my car has a white exterior. It was also a good time to change a burnt out light bulb in the cluster, as well, and I had dusted out and cleaned the cluster and the inside of the see through plastic to give it an almost new look:


Wrapped the lower intercooler tube with Thermo Tec exhaust wrap, which flows the cooled down air. Coupled with the custom double intercooler, 8" puller fan on the IC, this keeps the boosted air barely lukewarm. Even on a hot, heat soaked day, I peeled back the wrap a bit to touch the metal below it and it was still lukewarm, almost as if the car wasn't running. It's a good idea to wrap the lower IC tube as well, since it is extremely close proximity to the exhaust manifold.....a couple of inches away, and picks up a lot of heat from it.

Everything else in the engine bay on a hot summer day is either near scalding or getting there (including throttle body, etc), but the lower IC tube is virtually unaffected. Being that this is a daily driven car, I want the boost temps to be low, even if there's not much I can do about underhood temps (cowl hood or vented hood will eventually be ordered):


A view with all of the intercooler tubing re-assembled--it has a nice, stealthy, unassuming look on the lower IC, but the custom brushed aluminum supercharger top and upper intercooler tube with brushed "supercharged" pops out, nicely. Apologies for the dirty engine bay, it needs to be cleaned:


Painted the Thunderbird logo in the wheel center caps, using DupliColor spray paint. The center caps are pretty easy to find, so there's no need to worry in horror as a fairly rare car gets a custom touch. :) I masked off the caps, and then put clear tape over the logo, and then took an X-Acto knife to cut around it. The cut was a little off, so while the paint was still wet, i'd removed the tape and then dragged the X-Acto knife around the edge of the logo. I may eventually put a thin line of black around the logo, too, which would make it stand out even more:


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A picture of the car with the painted center caps. It adds a custom touch, but is subtle and is in keeping with the classy, understated look of these cars:



Active Member
I had re-ported the supercharger yet again. I had widened the top part of the "V", to mirror the rotor blades a bit better, and had gave the main edge a flatter edge, though there is still a beveled angle at the top. Feels like it added power, and the blower seems to have a higher pitched sound at part throttle at 5-7 psi.

latemodelm90re ported.JPG