Clevor Engine Intake Manifold Upgrade - Box Score

We're always talking about next-level performance for late-model Mustangs. Handling and engine-performance are the main points of focus, and typically, our mantra is the more, the better. This never- ending quest for performance has us always on the lookout for new products or methods of increasing-and-improving performance for '89-'13 Ponies.

In 2011, commissioning Coast High Performance to build a fuel-injected, 408ci Windsor with Trick Flow's new PowerPort 225cc Cleveland cylinder heads and R Series intake manifold (a Clevor engine) was one of the ideas we followed through on. Since that project's first report ("Hot In Cleveland," July '11), Greg Montoya nailed the hammer to the mat in our hard charge to learn more about the potential of this unique combination.

On this particular leg of the continued effort, we want to see the impact--negative or positive--of a simple intake- manifold swap on this Pony's unique bullet. This idea came about after Tech Editor KJ Jones and Gregg Changet at Trick Flow--although pleased with the Clevor's initial chassis-dyno results (432 hp/428 lb-ft without nitrous)--thought there was "a lot more power where that came from." We thought the Box R upper plenum intake manifold would be the best place to find it.

As we've explained in past reports, Trick Flow's Cleveland-style heads offer bigger valves, canted valve angles, large intake/slightly raised (0.100-inch) exhaust ports, and closed chambers. That makes them comparable to the Ford Aussie 2V and 4V heads of the '70s--heavy breathers that proved to be great performers on stroked engines.

Horse Sense: The dragstrip segment of this test, while successful, left us just on the edge of crossing one of the major performance plateaus for any regularly driven street/strip Mustang--the 10-second zone. Post-track investigation showed us that the clutch in Greg Montoya's '89 GT was thoroughly fragged, and it more than likely had been since our first runs on the chassis dyno. We're noting all this to reinforce how important it is to seat a new clutch before hammering a 'Stang on the chassis dyno or track. A new Centerforce Dyad will be backing up the 408 Clevor engine by the time you read this.

When you think about our Clevor's original induction setup, it's easy to understand how the long runners of the engine's Trick Flow R Series upper manifold actually decrease intake-air's (drawn through Anderson Ford Motorsports' 4-inch Power Pipe, Abbaco's 97mm DBX mass air sensor and a 90mm throttle body) velocity and efficiency, before passing into and through the large openings in the heads.

Replacing the standard R-Series upper-intake manifold with Trick Flow's famed Box R topper (PN TFS-51500008; $395.99) is a move that we're excited about. It should increase air volume in the manifold and shorten the distance that it actually has to travel. We strongly believed it would take the Clevor's naturally aspirated performance to a level that's more in line with the horsepower and torque values we all optimistically forecasted at the outset of the project.

Like many of you, Greg's a more-than-capable do-it-yourselfer and has handled all of the bolt-on assignments for Project Leave It to Clevor since the effort really hit full stride in our Sep. '11 issue ("Turning Tricks"). So with that said, check out the photos and captions highlighting the upper manifold exchange, and the compelling data that is a result of hitting both the dyno and the dragstrip immediately after the operation was completed.

On The strip

Shortly after the dyno test, we took advantage of a private test session at Auto Club Dragway that featured several project cars and motorcycles from Source Interlink Media's SoCal-based performance mags. Despite 85 degree temperature, density altitude that reportedly was close to 4,000 feet, and a clutch that was not doing well at all (see Horse Sense), Project Leave It to Clevor put down solid low-11-second runs across the 1,320.

While Greg's run notes are included in the caption for each timeslip, we must add that the GT carried a full fuel tank and tipped the scales at 3,500 pounds with Greg in the seat. Perhaps if we had removed the spare tire, jack, and full nitrous bottle (which we weren't using), approximately 50 pounds would have been gone and "official" 10-second e.t.'s could be claimed.

Run 1 (11.14/124.63 mph)
Run 2 (11.06/124.51 mph)
Run 3 (11.02 124.72 mph)

Of course, some tuning was necessary for achieving the mark, so we called on B&D Racing's Brian Schapiro for assistance in that area. Brian's nearly 20 years of experience with Anderson Ford Motorsports' PMS engine-management system has been huge for this project, as calibrations for naturally aspirated and nitrous-oxide performance have been spot-on every time. (For this effort, Brian only slightly modified his original WOT/dyno calibration for the Clevor, which resulted in the engine making just shy of 500 rear-wheel horses using Rockett Brand 100-octane fuel).

Conventional thought would lead one to think that taking away so much runner length (nearly 6 inches) would knock down rear-wheel torque by several lb-ft. As the data shows, this notion is totally dispelled for the Clevor engine.

Like the increased horsepower, torque with the new manifold is impressive. The peak hits 400 rpm in front of the torque generated with the R-Series plenum. Of course, with 3.73 gears and spool socked into the 8.8 rear of Greg's '89, we're pretty sure the tire-frying will be fairly instant through three gears whenever Greg nails the throttle on traction-limited pavement.

On The Dyno