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R-Spec Supercharger Kit For The 4.6L 3v

R-Spec Manifold

2005-2010 Mustang with 4.6L 3v

Make 650-1400rwhp!



We started working on the R-Spec when we realized that none of the available blower kits were big enough to support the horsepower numbers that have become common place amongst the hard core end of enthusiasts and hot rodders. The Kenne Bell 2.8L just doesn’t get the job done. The most we have ever seen one make is 844hp and that was on e85. That was it, the blower had no more. On pump gas we have never seen one make over 700hp. Big numbers yes, but in this day and age that is not at the top of the spectrum and to get those numbers the Kenne Bell is all maxed out and not real happy. Additionally the Kenne Bell has serious belt problems (which can be fixed with one of our belt kits, but that costs some coin), they run very hot (which can not be fixed without some serious custom fabrication) and we were never happy with the packaging of the Kenne Bell kits in general. So we decided to make our own kit based around the Whipple 3.4L Crusher (2.9L, 4.0L and 4.5L are options) which is an absolute monster capable of 1200+hp.

We have made 776hp on pump gas on our test car (octane limited) at 19.5psi and 981hp on race fuel at 24psi. Our test car’s motor is really not set up for this combination either. It is still a 4.6L, Stage I heads, Comp 127350 cams, 1 5/8” headers and 2.5” exhaust. If the motor were a 5.0L or a 5.3L Big Bore, had Stage III heads, 127550 cams (or custom), 1 3/4” headers and 3” exhaust it would make well into the mid 800’s on pump, well over 1000 with race fuel and probably as much as 1200 on e85. And the blower is still not being spun to its maximum RPM. If you want something you can make big power with on pump gas it doesn’t get any better than this. And if you want to make STUPID power on race fuel or e85 it can do that too.

Our first priority with the R-Spec kit was cooling. And we took a real hard look at this. These days it is not too hard to make boost, keeping the intake air temperatures (IAT’s) down to the point where they don’t hurt power on the other hand is the trick.

We already had the most efficient, best flowing, best cooling air to water intercooler (IC) designed and manufactured for the S197 Mustangs in our GT450 manifolds. So we took that design, made it even better, and ran with it.

Then we started to look at other cooling solutions. The IAT’s are not completely a byproduct of the blower discharge temps. The IAT’s are also effected by the heat being soaked into the intake manifold from the cylinder heads which run at 200+deg and the engine coolant that runs through the intake manifold which is anywhere from 175-225deg. Additionally there is a lot of radiant heat in the valley of the motor which heats the bottom of the manifold (the “pan”). These three heat sources transfer a LOT of heat into the aluminum intake manifold. And the intake manifold heats up the IAT’s considerably. When you want your IAT’s at about 100deg it doesn’t do you a whole lot of good to run them through a box (the intake) that is almost 200deg.

During our testing/investigation of IAT’s we found that the intercooler (IC) was actually not only cooling the blower discharge temps which is its job, but it was also cooling the body of the intake manifold because it was getting so warm from the heat transferred from the motor. Which is not not its job. You only have so much cooling energy at your disposal and you want to use that to cool the blower discharge temps, not the intake manifold.

1st mockup of the final production unit

Proven Design:

This design/combination is proven. There are a few other forced induction options out there that are not. Buyer beware. Just because something is for sale, doesn’t mean that it’s completely tested and proven.

We use Whipple superchargers. That’s pretty much all that needs to be said about that. Whipple has proven themselves in the performance industry over and over again. There is nothing out there that has higher quality standards than a Whipple.

As far as our stuff goes there isn’t much to prove. All we have done is design a few glorified adapters (that’s basically what a manifold is) and make them. A very nice, well thought out adapter, but an adapter none the less. There aren’t even any moving parts. That said the R-Spec design is a progression of our very popular and very proven GT450 manifold design. This isn’t our first rodeo.

The R-Spec intercooler is also a progression of our GT450. Same basic design, machining and production principles, just refined for this application.

The R-spec engine cooling changes are, to be frank, a rip off from the GT500. A prettier and more “custom” version, but a rip off none the less. The design principals were proven on the GT500 and our version proven out on our test car.

The belt system is based on our Kenne Bell 10 rib belt drive conversion kits. They have over 10,000mi of very hard testing on them.

We are exhaustive in our testing and product development. We do not use customers as our last step in our development process like some other manufacturers do.

Thermal Features:


Our GT450 IC (in the GT450 manifolds) is already the best performing intercooler you can get for a positive displacement S197 blower. But the R-Spec is something that we wanted on the cutting edge so we kicked things up a notch and designed an intercooler that absolutely CRUSHES everything else out there.

The start of this design process was to build a IC test rig with a “configurable” IC. The rig allowed us to test different IC designs, different restrictions, different pumps, etc. It was very, very educational. As far as we know no one has ever done this.

Right now the best performing IC available for a S197 aside from our GT450 is the stock GT500 unit which is a good benchmark. The Kenne Bell, Whipple, Roush TVS, Eforce, Saleen, etc IC’s range from “almost as good” as the GT500 to “not even close”. The GT500 IC’s are pretty good, but most of these guys have IAT problems still. So that is what we benchmarked our R-Spec IC against.

The R-Spec IC uses a Bell core and our own billet tanks. Bell is one of the biggest names in IC’s and their cores set the benchmark for the industry. The R-spec core has exterior dimensions that are 11% larger than the GT500. You can only stuff so much IC into an intake manifold, so doing something like using a core that is 2-3x the size simply is not an option. That’s not a problem though, core size is not what holds most IC’s back, water flow is. It sounds wrong at first but the IC is not what cools the IAT’s, the water running through the IC is. It’s pretty simple really, no or little water gets you no or little cooling. The water is what soaks up the heat and removes it from the IC/manifold. So, on a basic level you run the largest/best flowing core you can stuff in the manifold then feed that sucker a LOT of water. And water flow is where almost every IC out there has its problems.

The GT500 IC (and most others) have 5/8 fittings/restrictions…..and some smaller. And all of the other ones out there have sharp bends, some times more than a few, in their system. These small passages coupled with sharp bends are horrible for water flow. Yes, a lot of them use 3/4” hoses, but 3/4" hoses don’t make 5/8” restrictions bigger. The R-spec IC uses 1.25” fittings. Big deal right? 1.25” isn’t a whole lot bigger than 5/8”, is it? The answer is yes, a LOT bigger. A 1.25” passage flows up to 4 times the water a 5/8 passage does (depending on the pump used). That is a massive difference! And you want all that water flow. You may be thinking “But isn’t there a point where you are flowing too much or an unneeded amount of water?”. Yes, there is a point way out there where you are not getting any more returns on your water investment. But that is a long way off. You would have to run a fitting size/hose that is so big that it would literally be too big to get in/out of the IC core. So running too much water is effectively impossible.

In simple terms the R-Spec IC has up to 400%+ more cooling capacity than the next best one out there, the GT500. Mission accomplished!

The dirty little secret in the forced induction world is IAT’s. IAT’s are easy to keep under control on the dyno. So people see their 500-600-700-800hp dyno graph and happily drive off into the sunset thinking that they have that power all the time. Reality is a lot different than that. In real life, when you are driving around “heat soaked” you have a LOT less power. The computer starts to pull ignition timing (and therefore power) starting at an IAT of about 100deg (there are other factors though like coolant temp, etc). At an IAT of 136deg the computer starts pulling lots of timing and the hotter the IAT’s get the more power is pulled. Most people don’t realize (I would say 95% of them) that when they are driving around their IAT’s are in the range where timing is already being pulled. When they make a “pass” they will see IAT’s in the 150-200deg range, and have no power left. It is not uncommon for a 600hp car to make 500hp in real life. And the more power that is made the more power is lost. A lot of the IC’s out there are so underdeveloped that even the drag race cars that start with a cool system (at the track) and run ice water through the IC during a pass will have IAT’s high enough at the stripe that they will be pulling timing. And the guys on the street don’t have any of those advantages.

I don’t have to “sell” you anything when it comes to IC’s. Just set one of your gauges, SCT tuner, etc up to read IAT’s and go drive around. You will be horrified that you almost never have full power.

Engine Cooling Modifications

The first solution was to get the engine coolant in and out of the manifold as fast as possible (least amount of water touching the inside passages of the manifold). For this we looked to the GT500. On the GT500 the coolant goes straight up from the cylinder heads into the intake manifold, turns 90 deg and exits the motor. The water is only touching a small portion of the intake manifold. To accomplish this we had to run an external thermostat housing/bypass (like a GT500). We would have liked to keep everything “internal” like the 2007+ 3v’s do so there was less going on in front of the motor (mostly for aesthetics) but it has to be external if you want that heat out of the intake. An added bonus is that the new external system will flow a lot more water and unlike the stock 3v engine cooling system the R-Spec engine cooling system runs both banks of cylinders at the same temperature. On every other 3v setup one bank of cylinders runs hotter than the other.

Creating A Insulator/Heat Barrier Between The Manifold And the Motor

A TON of heat is transferred from the cylinder heads into the intake manifold. To prevent this we made the “bottom” of the manifold out of a composite. Basically the same stuff that Ford uses in their OEM composite manifolds. This composite barrier all but eliminates heat transfer from the cylinder heads into the intake manifold body. Additionally it is lighter than aluminum. This was a big move and as far as we know no blower manufacturer has gone to these lengths to prevent heat transfer and heat soak.

We also have the “Pans” ceramic coated to greatly reduce the radiant heat being transferred from the valley of the motor into the manifold.

The above thermal modifications greatly reduces the amount of heat being transferred into the intake manifold and therefore the heat being transferred to the IAT’s.

Alternator Upgrade:

Fitting a 3.4L on a 3v is no easy task. The biggest obstacle was that there wasn’t enough room between the back of the alternator and the fire wall unless we raised the blower considerably. Which would have had it sticking through most hoods. Obviously not a good solution. The second option was to remove the A/C compressor and move the alternator to that spot. For those that want to retain their A/C, which is most people, not a great plan. Add to that the stock Motorcraft alternators are JUNK we went with a custom alternator we have been designing for a while. The stock Motorcraft is a 6G based design that is nothing but problems. They don’t make much power (135A) and when spun up they come apart inside. There are 200A 6G’s out there, but they have the same issue with coming apart internally and they are even bigger than the 135A units, which is a real-estate issue. Ford stopped using the 6G alternators in 2010 because of too many warranty claims. Working with a friend who owns a very large alternator manufacturing company we came up with a 4G based design that allows us to run a smaller alternator that doesn’t come apart at high RPM’s and makes 215A. We custom modify the cases and the alternator “shop” hand builds each alternator. The alternator is necessary because it has to fit in very tight confines and most cars running big HP power need the extra power (amps) to run all the additional pumps, fans, etc that come along with that big power. Alternators aren’t sexy, but in this case much needed.

Belt Drive:

Belt drives are a huge issue on PD blowers. Even the most basic ones require a high zoot tensioner. Up the boost and RPM’s and either an 8 rib conversion or a 10 rib dedicated belt system are needed. Both cost some coin. And when you are looking at spinning the bigger blowers hard and making some serious boost a 8 rib conversion is not enough to get the job done, it has to be a 10 rib dedicated belt drive to be 100% reliable. When playing with a 3.4L Whipple the only choice is to go with a dedicated 10 rib belt drive. So we took what we learned from designing 10 rib belt drives for the Kenne Bell 2.6 and 2.8L blowers and applied it to the R-Spec. What you get is a bulletproof belt system that doesn’t slip, doesn’t chew up belts and for all intents or purposes is maintenance free. We even designed it around readily available belts that can be purchased at multiple sources. No custom belts involved.

Blower to manifold adapter plate:

Because we were starting from scratch we were not trapped into using a GT500 blower to manifold adapter plate bolt pattern which are absolute nightmares for getting the fasteners in and torqued. We designed or own adapter plate with easily accessible fasteners. This may not sound like much, but as GT500 guys with Whipples how much fun they are to get put on and how long it takes. It’s a mess. I’ve heard of some guys having their little kids get the fasteners started for them because they are the only ones with hands small enough. This is not something you have to deal with on the R-Spec.

Another nice “feature” is that you can remove the fuel rails and injectors while the blower is bolted to the manifold. In a lot of the big blower/big elbow combinations you have to remove the blower to get to the injectors/rails. That sounds like a nightmare!

Kit Includes:

-R-Spec intake manifold. Billet and composite
-Blower to manifold adapter plate. Billet
-3.4L Whipple supercharger with Crusher inlet and custom snout built to Department Of Boost Specs by Whipple
-10 rib dedicated belt drive system. Billet
-Thermostat housing/bypass block. Billet
-Lower radiator hose water manifold/bypass. Billet
-Engine coolant expansion tank. Aluminum
-215A 4G alternator with custom cases
-All required fasteners for items supplied

Kit Does Not Include:

-Fuel rails
-Fuel pump(s)
-Throttle body
-Cold air intake
-Heat exchanger
-Intercooler water pump
-Intercooler degass bottle/tank
-Fittings & hoses

This is a tuner kit. It would be impossible to put an entire kit together that would suit everyone's goals, tastes, budget, etc. A fuel system for 650hp on gas is a whole different story than a fuel system for 1200hp on e85 as an example. And supplying every kit with entry level stuff (which is what all complete kits do) would not be good enough for most buyers. You will need to figure out the rest of your combo based on your needs. We will of course be happy to help with that.

Additionally we have found that most buyers for this kit already have a blower (a small one). There isn't much point in re-selling them all of the ancillary items again.


R-Spec Manifold


(If paid by cash, check, money order, bank transfer)



2.9L Whipple -$550
4.0L Whipple +$650

Polished blower +$500
Powdercoated blower +$700

Polish manifold +$450
Polish belt kit +250

Anodize manifold +$350
Anodize belt kit +$200


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