Boost is a wonderful thing. That's why Carroll Shelby added the Paxton supercharger to the '66 GT350's option list. If you've never been in a blown Mustang, we recommend you avoid the experience unless you're prepared to install a supercharger on your own. Once you've experienced boost, you'll never want to go back to natural aspiration.
This is the Paxton supercharger system for '65-'68 small-block Mustangs. Major components include the NOVI 1500 supercharger and mounting bracket, the carburetor enclosure, the crankshaft pulley, elbow and ducting, a boost-referenced mechanical fuel pump, a belt, and a cleanable air filter. Our kit is for a driver-side installation, which isn't compatible with the factory configuration air conditioning or power steering. Passenger-side kits requiring battery relocation are also available. A separate system is available for '69 small-block Mustangs.
In 2002, Paxton reintroduced its supercharger system for '65-'68 Mustangs with carbureted small-blocks. Utilizing the modern, gear-driven NOVI 1200 supercharger and a carb enclosure similar to the original, Paxton's kit made supercharging accessible to the masses, not just to those who were able to piece together the rare and expensive components from Shelby's original system. This kit provides everything needed to supercharge a carbureted Ford small-block, including the mounting bracket, a boost-referenced mechanical fuel pump, a bypass valve, a crankshaft pulley, and a belt. Recently, Paxton made the NOVI 1500 available with the carburetor kit, so now there's a choice: boost, or even more boost.
Before embarking on a supercharger installation, there are some things you need to know. Boost works best with 8:1 to 9.5:1 compression ratios. If your small-block is set up for 10.5:1, consider replacing or modifying the pistons to drop it to 9.1:1, which Paxton considers ideal. If your engine is equipped with two-barrel induction, you'll need to swap to a four-barrel intake and carb. If you already have a street four-barrel with vacuum secondaries, you'll need to switch to a carb with mechanical secondaries because boost throws off the vacuum signal to the secondary diaphragm. In that case, consider upgrading to a carburetor from QuickFuel that offers more tuning possibilities than a standard Holley or Autolite. With a stock or Edelbrock Performer intake, the carburetor enclosure will fit under a factory hood; taller intakes may dictate the use of a hood with a cowl rise or scoop.
The NOVI centrifugal superchargers use engine oil for lubrication-oil needs a way to flow from the engine, through the supercharger, and back into the oil pan. Paxton provides fittings and hoses to obtain oil pressure from the oil-pressure sending-unit port in the engine block. Some cringe at the thought of punching and tapping a hole in the oil pan for installation of the oil return-line fitting, but the Paxton instructions detail how to do it in the car without the risk of metal shavings or paint chips falling in.
Paxton offers the NOVI 1200 and 1500 superchargers with the vintage Mustang kit. We elected to go with the 1500 for Steven's modified 289. Similar to all NOVI superchargers, it features Paxton's race-proven gearcase, steel helical-cut gears, and direct engine oiling.
You may have to make some sacrifices for the pleasures of boost. Paxton offers options for installing the supercharger on either side of the engine. The passenger side requires the relocation of the battery; with a driver-side installation, you have to give up air conditioning and power steering unless you're willing to improvise.
Paxton supplies a comprehensive kit designed to bolt on to a stock '65-'68 small-block, but it can't anticipate the various modifications made to older Mustangs. Wider radiators can interfere with the crankshaft pulley, aluminum Cobra-style oil pans require removal for drilling and tapping for the oil return fitting, and carburetors may require linkage modification to fit inside the enclosure. Be aware of possible interference problems with larger, late-model-style distributor caps and some valve covers. On '65-'66s with the factory 5/16-inch fuel line, plan to upgrade to at least a 3/8-inch line. In other words, be prepared to replace components and tweak others. Don't worry-it will be worth it.
The other major component of the Paxton system is the carburetor enclosure. Made from cast aluminum, its finned top maintains a vintage appearance, similar to the enclosure from the '60s. The lower half includes a linkage for simple throttle connection and adjustment. Factory '65-'68 hoods clear the enclosure when used with stock or low-riser aftermarket four-barrel intakes. High-riser intakes require the switch to a taller hood, such as an aftermarket cowl-induction version. | 
Steven wanted to retain his stock hood, so additional clearance was gained by utilizing Ron Morris Performance adjustable motor mounts from Mustangs Plus. The mounts lower the engine 1/2 inch, and they're adjustable from front to rear and side to side. Steven's Edelbrock RPM Air-Gap intake was also swapped for a lower-profile Edelbrock Performer. | 
When we arrived at Cobra Restorers, tech Patrick Kelley had already installed the fitting for the oil drain line in Steven's aluminum Cobra oil pan. Paxton's instructions detail how to punch a hole in standard sheetmetal oil pans for the fitting, but for the aluminum, Patrick pulled the pan for drilling and tapping. In either case, take care to prevent shavings, paint chips, and other debris from falling into the pan. Paxton provides detailed instructions. |
Paxton supplies a T-fitting for the oil-feed line, but Patrick felt a modified factory-style fitting would work better with the vintage theme of the car. It's actually an oil-pressure sending-unit extension that was used on GT350s. Patrick drilled and tapped the extension for the oil feed line. Also shown in this photo is the Paxton-supplied boost-reference fuel pump. It allows the pump to increase fuel pressure in proportion to boost. | 
Paxton's crankshaft pulley replaces the factory pulley to provide a spot for the supercharger belt. Paxton provides bolt patterns for three- and four-bolt balancers. In our case, the pulley was bolted to an SFI-approved ProSport balancer, replacing the 289's original crankshaft version. | 
For Steven's supercharged 289 application, QuickFuel recommended its 650-cfm street carburetor (PN SS650AN), with annular boosters and mechanical secondaries. Before bolting it on the 289, Patrick mocked up the carburetor and enclosure installation on a nearby 302 so he could determine if there were any linkage and clearance issues. |