I’ve finally found a valid comparison and it turns out that the common belief is is wrong. In fact, the TFS Box R is the better set up for a street-oriented 302-based stroker combo. I’ve really wondered about this for a long time, and have always thought about swapping my box upper for a standard TFS-R upper.
Hopefully, this will help someone out there that tries to do the research prior building their combos.
From “Dyno-proven Small-block Ford Performance”:
From Caption one, a picture showing the upper intake dismantled:
From Caption two, a picture showing the Box R upper side by side with the standard TFS-R upper:
From Caption three, a dyno graph comparing the horsepower curves from 3000 rpm to 6000 rpm:
From Caption four, a dyno graph comparing the torque curves:
Now, the following dyno comparison test in this book makes the Box R’s advantage even more clear. On the same motor with the box upper, a 75mm TB is swapped with a 90mm TB and yields a max of a 14hp gain at 5800 rpm and 12 ft-lbs at 5600 rpm. I don’t think the standard TFS-R upper will even accept a 90mm TB. Peak power jumps from 441 to 454 hp on this motor. I think this number would be the more valid comparison to the standard upper.
So in conclusion, the difference of 39 peak hp (415 vs. 454) without any loss in low end TQ on a 331W with otherwise very street-oriented parts dispels the myth/conventional wisdom that Box intakes are only for high revving strokers. Additionally, based on the author’s experience, the common belief that Box intakes are somehow advantageous to their counterparts in boosted applications is also false.
If this surprised you, be honest It surprised me. Frankly, I expected the Box to come out on top at peak, but also expected it to suffer in low and midrange power, whereas it matched on the low, and outmatched even in mid-range. Thoughts?
Hopefully, this will help someone out there that tries to do the research prior building their combos.
From “Dyno-proven Small-block Ford Performance”:
Before getting to this test, I have to admit not being a big fan of these so-called box upper intakes. Testing in the past, both for my previous 5.0L book and a great many magazine articles, has revealed the lack of runner length to be terribly ineffective for the vast majority of street applications, including supercharged and turbocharged engines. This test demonstrated the importance of keeping an open mind and continuing to test. The 331 test engine consisted of a Coast High performance stroker assembly with a 4.030-inch bore, a 3.25-inch stroke, and a set of forged connecting rods. The 331 was further equipped with an XE274HR cam, providing a .555/.565 lift split, a 224/232 duration split at .050”, and a 112-degree lobe separation. This cam has proven effective for a great many street-oriented 5.0L-based buildups. Both TFS upper intakes were fed by a 75 mm Holley throttlebody and matching EGR spacer, while the fuel was supplied by a set of 36lb injectors. The engine was also equipped with an MSD distributor, a set of Hooker headers, and the FAST management system. The heads were CNC ported 185cc TFS Twisted Wedge Heads.
While I was hard pressed to recommend a box upper intake for anything but a high-rpm or possibly a large-displacement stroker combination, the new TFS Box R upper had something going for it that the other designs did not, namely increased runner length. Unlike early attempts, the TFS Box R upper intake featured extended runners into the common plenum. It is this extra runner length, combined with a straight shot from the upper through the effective lower and into the head port, that helps produce an effective power curve. Swapping in the new Box R upper intake in place of the TFS R upper intake resulted in a significant jump in power, from 415hp to 441 hp. Even more impressive, given the box design, was the fact that the increase in power from 4800 rpm to 6,000 rpm cost little to no power elsewhere in the rev range. There was a slight drop in power, roughly 4 ft-lbs, at 3700 rpm, but this was offset by a gain of the same amount at 3200rpm. Unlike the previous testing on these box-style upper intakes, the TFS version offered impressive power gains from below 4000 rpm without any low-speed penalty. That it looks cool and fits over raised valvecovers is just icing on the cake.
From Caption one, a picture showing the upper intake dismantled:
“A peek inside the Box R upper intake reveals the short runners and radiused port entries. This design also lends itself to porting to further improve air flow.
From Caption two, a picture showing the Box R upper side by side with the standard TFS-R upper:
“Both TFS intakes relied on the same lower manifold. The difference in runner length between the two designs is evident in this photo. The TFS R (right) offered longer runners while the Box R offered shorter runners and increased plenum volume.
From Caption three, a dyno graph comparing the horsepower curves from 3000 rpm to 6000 rpm:
“Obviously the Box R upper intake was the clear choice for this 331 stroker engine. Though the power gains posted by the Box R were most prevalent past 4500 rpm, the gains came with little or no tradeoff in power below that point.
From Caption four, a dyno graph comparing the torque curves:
“With the exception of a minor drop at 3,700 rpm, the Box R upper intake bettered the TFS R upper intake from 3000 to 6000 rpm. Note the huge torque gains between 5,000 and 5,500 rpm. Torque production with the Box R upper intake was up by as much as 21 ft-lbs at 5,200 rpm.
Now, the following dyno comparison test in this book makes the Box R’s advantage even more clear. On the same motor with the box upper, a 75mm TB is swapped with a 90mm TB and yields a max of a 14hp gain at 5800 rpm and 12 ft-lbs at 5600 rpm. I don’t think the standard TFS-R upper will even accept a 90mm TB. Peak power jumps from 441 to 454 hp on this motor. I think this number would be the more valid comparison to the standard upper.
So in conclusion, the difference of 39 peak hp (415 vs. 454) without any loss in low end TQ on a 331W with otherwise very street-oriented parts dispels the myth/conventional wisdom that Box intakes are only for high revving strokers. Additionally, based on the author’s experience, the common belief that Box intakes are somehow advantageous to their counterparts in boosted applications is also false.
If this surprised you, be honest It surprised me. Frankly, I expected the Box to come out on top at peak, but also expected it to suffer in low and midrange power, whereas it matched on the low, and outmatched even in mid-range. Thoughts?