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400 Small Block Chevy - Vortec Heads

400ci Engine Blueprinted

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Testing Day

With an increase of two full points of compression and good ring seal, we expected some serious power improvements over the stock baseline, and we weren’t disappointed. Right at the first pull on the dyno with 36 degrees of timing (versus 44 degrees with the old engine), the 406 grunted out 486 lb-ft of torque compared with the previous 458 and produced between 20 and 30 lb-ft of torque increase across the board with similar gains in horsepower with the peak of 436 hp at 5,200 rpm. The biggest problem now seemed to be that we needed some way to make the engine breathe better at higher engine speeds to make more horsepower. The limitation seemed to be valve lift, so we thought the simple addition of a set of 1.6:1 rocker arms might help.

Generally, an increase from 1.5:1 to 1.6:1 rockers is usually worth about 0.030 inch of valve lift, and since our cam barely made 0.490-inch lift, that seemed like a good solution. We also tried a 1-inch-tall Wilson tapered spacer that was worth roughly 3 hp at the peak with no loss of torque down low. We also drained the 10W-30 break-in oil and tried some thinner-viscosity Lucas 0W-20 race oil, hoping to push over the 500-lb-ft plateau. All these little efforts really paid off. The rockers alone were worth almost 20 hp, which helped us excel to 501 lb-ft of torque and upped peak power to 466 hp at 6,000 rpm, and the engine responded positively to nearly all the changes. All this really proves that quality machine work and proper engine assembly techniques really do pay off with big rewards. We are already thinking about how to make even more power with this 406ci, and we might have to start calling it the BFH because it brings down the big freakin’ hammer on torque.

Power Curves

This graph illustrates the big differences in torque between the previous combo and our latest version. Note how the shape of the curves remains basically the same, since we did not change the cam, heads, intake, or exhaust. But look carefully at how the horsepower curve dips slightly between 5,300 and 5,900 on Tests 2 and 3. The dip is more pronounced in Test 3, which is where we added the rocker ratio. Our theory is that the valvesprings are right on the ragged edge and became “fussy” in this rpm range. The fix is a different (not necessarily higher load) valvespring that would probably take care of this. The big news is the huge gain in torque between Test 1 and Test 3. This would make an excellent street engine.

Dyno Numbers

Test 1 is the best power we pulled from the original test of the engine from the May ’11 issue. Test 2 is with the same Bow Tie Vortec heads, Comp cam, Weiand intake, Holley carb, and dyno exhaust with no mufflers. Test 3 added a Wilson-tapered carb spacer and a set of Comp 1.6:1 roller rockers and performance pushrods.

Power Curve

RPM Test 1 TQ Test 1 HP Test 2 TQ Test 2 HP Test 3 TQ Test 3 HP TQ/HP Gain
2,800 392 209 --- --- --- --- ---
3,000 389 222 --- --- --- --- ---
3,200 410 249 450 274 449 274 +39/25
3,400 433 280 462 299 468 303 +35/23
3,600 447 307 474 325 483 331 +36/24
3,800 457 331 484 350 495 358 +38/27
4,000 458 349 486 370 501 381 +43/32
4,200 452 361 485 387 501 401 +49/40
4,400 444 372 480 402 497 417 +53/45
4,600 438 383 473 414 491 430 +53/47
4,800 430 393 465 425 482 440 +52/47
5,000 418 398 455 434 472 449 +54/51
5,200 404 400 440 436 453 449 +49/49
5,400 390 401 417 429 434 446 +44/45
5,600 374 399 400 427 423 451 +49/52
5,800 355 393 388 428 417 461 +62/68
6,000 333 380 373 426 408 466 +75/86
6,200 --- --- --- --- --- 454 ---
Peak 458 401 486 436 501 466 ---
Avg.* 417.2 357.2 450.4 390.0 465.5 400.3 ---

*Average power numbers were calculated between 3,200 and 6,000 rpm to ensure a fair comparison.

Parts List

Description PN Source Price
Used 400 short-block Used Junkyard $120.00
Scat crank, rod, piston balanced Call Scat Summit Racing 1,496.95
Scat 6.00-inch I-beam rods 26000 Summit Racing 251.95*
Icon forged piston, -51cc dish IC758 Summit Racing 475.95*
Vortec Bow Tie, large-port 25534446 Scoggin-Dickey 985.70
Comp 1.6:1 roller rockers 1016-16 Summit Racing 351.95
Comp Muscle Car 10W-30 oil 1594 Summit Racing 39.75
MSD Distributor, pro billet 8361 Summit Racing 212.95
ARP 400 main studs 234-3701 Summit Racing 77.18
ARP head bolts 134-3701 Summit Racing 108.95
Federal-Mogul cam bearings 1404 Jeg’s 23.99
Federal-Mogul main bearings 140M Jeg’s 65.95
Federal-Mogul rod bearings 7100CH Jeg’s 56.99
Federal-Mogul rod bearings -1 7100CH-1 Jeg’s 86.99
Fel-Pro align bore main seal 2909 Summit Racing 23.95
Fel-Pro 400 head gasket 1044 Summit Racing 141.98 pr.
Fel-Pro 1-pc pan gasket 1880 Summit Racing 40.95
Fel-Pro Vortec intake gasket 1255 Summit Racing 32.99
Professional Products balancer, 6.75 80000 Summit Racing 54.95
Federal-Mogul oil pump pickup Z2241246 Summit Racing 11.95
Federal-Mogul cam bearings Z1235M Summit Racing 17.95
Federal-Mogul oil pump drive Z2246146 Summit Racing 8.95
Sealed Power brass freeze plug Z381 Summit Racing 18.95
VHT Chevy orange paint DE1620 Summit Racing 6.95
GMPP self-align 3/8-inch rockers 12495490 Summit Racing 61.95
Weiand Speed Warrior intake 8501 Summit Racing 209.95
Holley 750 mechanical-secondary carb 0-4779 Swap meet 150.00
Comp nitrided Thumpr hydraulic cam 12-601-20 Summit Racing 274.95
Comp Pro Magnum hydraulic lifters 858-16 Summit Racing 94.95
Bosch Super + spark plugs 7975 Auto Zone 15.92
Wix oil filter 51069 Summit Racing 5.95
Wilson tapered 1-inch spacer 004110 Wilson Manifolds 128.75
Subtotal 4,929.34
Machine Work 810.00
Grand Total $5,739.34

Machine Work

Operation COST
Hot tank block $60.00
Bore and torque-plate-hone 290.00
Align-hone block 190.00
Deck block 190.00
Install cam bearings 60.00
Hone damper 20.00
Machine Work total $810.00

*These separate part numbers and prices for the pistons and rods are for reference.

SOURCES
Scoggin-Dickey Parts Center
5901 Spur 327
Lubbock
TX  79424
800-456-0211
www.sdparts.com
Wilson Manifolds
Ft. Lauderdale
FL
954-771-6216
www.wilsonmanifolds.com
Comp Cams
3406 Democrat Road
Memphis
TN  38118
800-999-0853
www.compcams.com
United Engine & Machine Co.
Carson City
NV
800-648-7970
www.kb-silvolite.com
Summit Racing
Akron
OH
800-230-3030
330-630-0240
www.summitracing.com/
Barrington Engines
Van Nuys
CA
818-442-9409
GM Performance Parts
P.O. Box 33170
Detroit
MI  48232
800-577-6888
www.gmperformanceparts.com
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