It's safe to say we've built a few 350 Chevys in the pages of Car Craft the last couple decades or so. The same cannot be said about Ford's similarly sized counterpart, something we will remedy this month and in subsequent issues this year. Like our Blue Collar big-block Chevy, we will keep the recipe simple: start with stock parts first, then make sensible upgrades in search of the best-bang-for-the-buck parts. IMM Engine & Dyno in Indio, California, tackled this build, with owner Brian Hafliger even doing double duty as builder and photographer while your author was road tripping in an Oldsmobile (see page 56 of this issue).
Let's spare the drama and get to the results right away. Starting with a bone-stock 351W truck engine, we bored the block 0.020-inch over, fitted KB flat-top pistons to the stock crank and rods, installed a Crane hydraulic roller cam, and reassembled the engine with GT40 cylinder heads. That combination was good for 391 hp at 5,900 rpm and 405 lb-ft at 4,300 rpm. After that, we dropped Trick Flow's 11R cylinder heads on the same short-block and made 505 hp at 6,700 rpm and 451 lb-ft at 5,200 rpm. Along the way, we shuffled a few intake manifolds and carburetors across this engine, and the test results are interesting.
The foundation of the build is simple: a truck engine from the 1990s. It came with a roller cam and a one-piece rear main seal from the factory. We got the long-block for free from a guy who was running it in a turbocharged Fox-body Mustang. It was past worn out; he decided to upgrade to an aftermarket block and just wanted to get rid of this engine.
This engine had detonated quite a bit under boost and needed to have the main cap registers repaired and the main caps align-honed. The crankshaft and connecting rods all checked out OK, though. The cylinders cleaned up with a minimal 0.020-inch bore and hone that Brian performed using BHJ torque plates.
The crank and rods were reused, and Brian installed a new Melling high-volume oil pump. We spec'd ARP bolts throughout the build.
For this iteration, we decided to use a set of KB flat-top hypereutectic pistons. They come with 6.5cc valve reliefs and 1⁄16-, 1⁄16-, and 3⁄16-inch rings. Brian mocked up pistons in all four corners to measure, then surfaced the block to set the pistons at zero-deck. In nearly all circumstances, you can reuse stock roller lifters, but ours were pretty rough from sitting for a while, so Brian replaced them with a set of Crane's OE replacement roller lifters. The cam measures 228/236 degrees duration at 0.050-inch lift and 0.552/0.574-inch lift. It's an off-the-shelf Crane cam, but Brian asked for it to be custom-ground on a 108-degree lobe-separation angle instead of the standard 112-degree LSA.
The GT40 heads needed some machining prior to installation. Brian first cut the guide bosses and spring pads for valvespring locators. Next, he used a reamer to increase the diameter of the GT40's bolt holes to match the 351's thicker-diameter head bolts.
He also machined the rocker-arm stands for Crane's stud conversion kit. We used Crane's 1.6:1 roller rocker arms, and using a set of checker valvesprings, piston-to-valve clearance with the GT40 heads was an ample 0.180 inch. For the test, we used Crane's 448-lb/in dual valvesprings to match the cam. Valve float was nonexistent, even at engine speeds approaching 7,000 rpm.
Here is the GT40 combination ready to run. With 0.040-inch head gaskets, the compression ratio was 10.0:1. We used Doug's headers for all the tests. Brian chose them because the combination of 30-inch-long, 13⁄4-diameter primary tubes and short 3-inch collectors complemented the cam and heads better than most other headers available with longer primaries. Per his normal dyno setup, Brian used MSD's Ready-To-Run distributor and their electric water-pump drive. We used Torco 10W-30 oil and 91-octane gasoline from the local Chevron. This combination made best power with 29 degrees total timing.
The heads were machined to accept a set of 1.90/1.55-inch valves (the intakes are slightly larger than the stock 1.87-inch valves). Brian selected a set of Ferrea valves, and no other machining or porting was done to the GT40 heads other than the valve job.
We used this opportunity to test a few different intake manifolds. From left to right: Edelbrock Victor Jr., Summit Racing dual plane, and Edelbrock Performer RPM Air Gap. Each manifold fit both the GT40 and Trick Flow heads flawlessly.
In addition to swapping manifolds, Brian cycled through a trio of carburetors, starting with Edelbrock's Thunder Series 650-cfm AVS. "This engine just wanted more air," Brian exclaimed. No matter which cylinder heads were installed, the engine made best power with the bigger carb. With GT40 heads, the 750 Double Pumper worked best; with the 11R heads, the 1,000 HP carb was the winner.
After making pretty decent power with GT40 heads, Brian removed them for Trick Flow's relatively new 11R heads. Available in 205- or 190cc intake runner sizes, we choose the latter for this test. Both versions of the 11R are fully CNC ported.
On the Dyno
All testing was performed on IMM's DTS engine dynamometer, and the results listed are adjusted according to the SAE correction factor. Doug's 13⁄4-inch primary tube headers were used throughout.
Test 1: GT40 heads, Edelbrock 650 AVS, Summit Racing intake manifold
Test 2: GT40 heads, Holley 750 Ultra Double Pumper, Summit Racing intake manifold, 1-inch open spacer
Test 3: 11R heads, Holley 750 Ultra Double Pumper, Edelbrock RPM Air Gap intake manifold
Test 4: 11R heads, Holley 750 Ultra Double Pumper, Edelbrock Victor Jr. intake manifold
Test 5: 11R heads, Holley 1,000 HP, Edelbrock RPM Air Gap intake manifold
Test 6: 11 R heads, Holley 1,000 HP, Edelbrock Victor Jr. intake manifold
Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 RPM HP TQ HP TQ HP TQ HP TQ HP TQ HP TQ 3,000 211 369 215 378 224 393 216 379 — — 222 389 3,200 233 383 238 390 247 406 238 392 — — 241 395 3,400 250 386 257 397 264 408 257 397 — — 256 395 3,600 265 387 272 398 282 411 271 396 284 415 272 397 3,800 280 388 289 400 304 420 290 401 308 425 291 402 4,000 299 393 306 402 326 429 313 411 330 434 313 411 4,200 314 393 323 404 350 438 334 418 352 440 338 423 4,400 327 390 337 403 371 443 358 427 373 446 362 433 4,600 336 384 349 398 391 446 381 435 395 451 386 441 4,800 346 378 358 392 410 448 400 438 414 453 407 445 5,000 355 373 368 387 425 447 420 441 431 453 428 449 5,200 363 366 376 380 442 447 440 444 448 452 447 451 5,400 371 361 384 373 452 440 456 444 459 447 461 449 5,600 375 352 387 363 465 436 470 441 469 439 475 446 5,800 379 343 390 353 476 431 484 438 472 427 487 441 6,000 378 331 388 340 478 418 489 428 482 422 494 433 6,200 — — 384 325 478 405 490 415 484 410 495 419 6,400 — — — — 480 394 489 401 485 398 503 412 6,600 — — — — 482 383 497 395 491 390 504 401 6,800 — — — — 482 378 494 387 490 384 505 395
The 11R's combustion chambers are fully CNC-profiled as well. The valve angles differ slightly from the traditional Twisted Wedge design. Pistons with valve reliefs specifically made for Twisted Wedge heads will still work with these heads, though. Two combustion chamber sizes are available: 56cc and 66cc. We chose the former, yielding a 10.7:1 compression ratio, in conjunction with Trick Flow's Cometic MLS head gasket.
Because they're simply taller than production Ford cylinder heads, the 11Rs needed pushrods that were nearly 2 inches taller than stock. Brian chose a set of 5⁄16-inch, 0.080-wall-thickness pushrods from Manley. These measure 8.250-inch. The stock pushrods were 6.375 inches long.
Doug's 13⁄4-inch headers were used again to test the 11R heads. Brian installed a set of NGK FR5 spark plugs, and this combination ran best on 30 degrees of total timing.
Our KB pistons weren't designed with Twisted Wedge valve reliefs, so Brian paid close attention to valve clearances. He needed to grind the intake valve relief angle slightly, but was able to create a safe 0.120-inch clearance on the intake side with the cam installed straight up.
Though tested with an RPM Air Gap (installed here) and 750-cfm Ultra Double Pumper, this combination made best power with Holley's 1,000 HP carburetor on a Victor Jr. intake. Compared to the best power made with the GT40 heads, just the addition of Trick Flow's 11R heads yielded an increase of 121 hp with no loss in torque anywhere in the powerband. Want even better news? This cam really isn't big enough to take advantage of the full potential of these cylinder heads. We will explore that limit more fully in our next installment with a bigger cam and more displacement. No matter what, Trick Flow's 11R cylinder heads offer an incredible bang for the buck. End
