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495 HP at 7,400 Small-Block Ford Build

This is the correct way to build a 500hp small-block Ford that just begs to be revved. Trust us.

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While car crafters are more into horsepower than math equations, the one formula most performance enthusiasts are intimate with is: horsepower = torque x rpm 5,252.

Big engines rely on lots of displacement to make torque and horsepower, but with smaller engines, the approach is to rev it high. Push the torque higher in the rpm band, and you'll make more horsepower. As an example, 400 lb-ft at 4,000 rpm equates to 304 hp. But that same 400 lb-ft at 6,500 rpm is a smokin' 495 hp.

Among the little V-8 engines, the most popular has to be the 302ci small-block Ford. While the rest of the world is building ever-larger engines, the little Blue Oval pushrod 5.0L continues to surge in popularity. Lately, Car Craft has been playing around with different 302 Ford combinations, so this time we decided to punch up the displacement a little while still relying on rpm to deliver a big horsepower number. While 347ci strokers are OK, we decided to go with the shorter 3.25-inch arm and build a 331ci screamer.

Our goal was aggressive yet simple: build a normally aspirated pump-gas 331ci small-block Ford that could make 1.5 hp per cubic inch that wouldn't explode all over the place. You've probably already skipped down to the dyno test, so you know we came really close 500 with 496 hp at 7,400 rpm that is dead reliable.

CC contributor Tim Moore built this engine, and it's currently scheduled as the motorvation for his Dan Gurney Trans-Am-tribute '67 Cougar. Just the thought of spinnin' this small-block up to 7,500 rpm and bangin' Fourth gear coming off Turn 6 at Willow Springs sounds like a great way to spend a Saturday afternoon.

Building Blocks
The 331ci small-block Ford is a classic stroker package that combines an excellent bore and stroke combination that can withstand the kind of rpm abuse Moore had planned. The stock 302 Ford small-block combines a 4.00-inch bore with a 3.00-inch stroke. To get to 331 inches, Scat offers a forged steel crank with a slightly longer 3.25-inch stroke that matches nicely with a 4.030-inch bore.

Heads And Cam
The one place "bigger is better" works is where the goal is lots of horsepower at high engine speeds. Since Moore is aiming for engine speeds in excess of 7,000 rpm, he was less concerned with low-speed torque. That's why he decided on a set of Air Flow Research 205cc runner wedge heads for his 331 spinner. AFR offers four different intake-port-volume cylinder heads, from the high-velocity 165cc and 185cc heads to the larger 205 and top-billing Outlaw 225cc monsters. Moore decided to go with the 205cc Outlaw castings that AFR claims will flow more than 300 cfm above 0.550 inch of valve lift on the intake. Packaged with 2.08/1.60-inch intake and exhaust valves, these heads can get with the program, especially with their much more efficient exhaust ports AFR says can generate 225-cfm-plus numbers above 0.500-inch lift. Taking nothing away from the impressive intake flow numbers, it's important to have good exhaust ports if you want to make serious horsepower. With strong exhaust port flow we can minimize the amount of additional camshaft exhaust duration necessary to make maximum horsepower.

Moore went with a Comp Cams mechanical roller, since there's really no reason for a hydraulic cam to be spinning more than 7,000 rpm. The advertised specs look especially big at 274/280 for a 331ci engine, but at 0.050-inch tappet lift, the numbers come in at 236/242 degrees. To be technically accurate, we also have to subtract 1/2 degree per 0.001 inch of lash that is required for clearance to compare these mechanical lifter numbers with what most enthusiasts recognize as hydraulic cam numbers. With 0.16 inch of intake lash, subtract 8 degrees from the 0.050 duration numbers, which reveals the true specs of 228 degrees of duration at 0.050-inch tappet lift. We combined good Comp mechanical roller lifters, 0.080-inch-wall-thickness Comp Hi-Tech pushrods, and a set of 1.6:1 Pro Magnum roller rockers, tied in with the ARP 7/16-inch rocker studs and AFR roller cam valvesprings-and never once experienced valve float difficulties. This immediately motivated us to consider swapping to a set of 1.7:1 roller rockers, but we ran out of time before we could take this engine to that next level.

CAM SPECS
Camshaft Duration
(Advertised)
Duration
(at 0.050)
Lift LASH Lobe
Separation
Comp roller (intake) 274 236 0.602* 0.016-inch 110
35-770-8 (exhaust) 280 242 0.608* 0.018-inch  

These are gross valve-lift numbers that do not take into account the lash. Subtracting the lash creates a net intake lift of 0.586 inch and an exhaust lift of 0.590 inch. These numbers are based on a 1.6:1 rocker ratio.

Test Day
Our first pull to check the air/fuel ratio indicated where we were headed when torque was still climbing at 5,000 rpm. We ran a Holley 750-cfm Street HP carburetor and an Edelbrock Super Victor single-plane intake manifold, and the fuel curve was incredibly steady allowing us to concentrate on optimizing the package. With peak torque at 5,600 rpm, the horsepower peaked at 7,400 rpm with 480 hp. Not only is this almost directly on top of our 1.5hp/ci goal, but it's also very repeatable with several runs at that level. Timing and jetting changes produced a few minor improvements, and then we bolted on a Wilson 1-inch open spacer that finally helped us kick the peak power up to 496 hp.

With an 1,800-rpm powerband between peak torque and peak horsepower running a solid 1.5 hp/ci and plenty of durability, there's little more we could ask of this stroked-block Ford other than maybe 4 more horsepower so we could claim 500. In post-testing discussion with AFR's Tony Mamo, he suggested the 185cc Outlaw Street heads would probably have made the same peak power while also pumping up the midrange torque slightly. Here's a case where being a little more conservative might have made even more power. How can you lose on a deal like that? We also have to admit that in the car, these numbers will drop a little after fitting the engine with chassis-style heads, an accessory drive, an air cleaner, and other accouterments that must accompany a street-driven engine. But the fact remains that this is one stout small-block Ford.

Dyno Tales
Test 1 is the initial test as configured in the initial buildup of the engine, including the AFR 205cc heads, Comp mechanical roller cam, Edelbrock single-plane Victor intake, 750-cfm Holley HP carburetor, and 13/4-inch headers with open exhaust.

Test 2 added a 1-inch open spacer to the intake manifold, with all other components remaining the same.

  TEST 1 TEST 2
RPM TQ HP TQ HP
3,600 368 252 367 251
3,800 375 271 371 268
4,000 378 288 378 288
4,200 385 308 384 307
4,400 390 327 390 326
4,600 395 345 393 344
4,800 400 366 397 363
5,000 408 389 405 393
5,200 414 410 408 404
5,400 416 428 412 423
5,600 416 443 413 440
5,800 416 456 412 455
6,000 410 468 411 469
6,200 406 479 407 480
6,400 399 486 398 485
6,600 388 488 389 489
6,800 375 486 377 488
7,000 366 488 366 488
7,200 359 493 359 493
7,400 350 493 352 496
Peak 416 493 413 496
Average 390.3 411.2 391.3 412.2
PARTS LIST
DESCRIPTION PN SOURCE PRICE
AirFlow Research 205cc heads 1450 Buyafr.com $1,838.19
ARP head studs 154-4203 Summit Racing 149.95
ARP intake bolts 454-2001 Summit Racing 31.95
ARP flywheel bolts 200-2802 Summit Racing 10.95
ARP balancer bolt 150-2501 Summit Racing 20.95
ARP oil pan stud kit 254-1901 Summit Racing 42.95
ATI balancer 918895 Summit Racing 369.95
Autolite spark plugs, race plugs AR-3923 Summit Racing 21.52
Clevite main bearings MS590H Summit Racing 69.95
Clevite rod bearings CB634H Summit Racing 10.25
Clevite cam bearings SH1321S Summit Racing 21.69
Comp Cams street roller cam kit CL35-770-8 Summit Racing 599.95
Comp Cams roller rockers, 1.6:1 1332-16 Summit Racing 285.95
Comp Cams timing chain set 3135 Summit Racing 69.95
Comp Cams pushrods 7937-16 Summit Racing 153.39
Edelbrock Super Victor intake 29285 Summit Racing 389.95
Ford Mexican 302 block used Swap meet 300.00
Holley 750-cfm HP carb 80528 Summit Racing 663.95
Mahle piston, 4.030-inch bore SBF165030F06 Summit Racing 680.95
Milodon oil pan 31600 Summit Racing 349.95
Milodon oil pump 18800 Summit Racing 78.69
Milodon oil pump pickup 18485 Summit Racing 57.39
Milodon oil pump shaft 22500 Summit Racing 20.95
Milodon windage tray 32210 Summit Racing 49.95
Milodon install kit 81157 Summit Racing 37.95
MSD billet distributor 8598 Summit Racing 268.60
MSD plug wires, universal 31189 Summit Racing 80.60
Scat 4340 steel, crankshaft 43022 Summit Racing 561.95
Scat H-beam rod, 5.400 inches 65400927 Summit Racing 399.95
TFS Ford main girdle 51500700 Summit Racing 204.95
Victor MLS head gasket MLS-54290 N/A --
Victor oil pan gasket OS32491 N/A --
Victor rear main seal JV730R N/A --
Victor timing cover gasket JV856 N/A --
Victor intake gasket 95197SP N/A --
Victor valve cover gasket VS50203 N/A --
Victor header gaskets 95177SG N/A --
Wilson 1-inch spacer 000010 Summit Racing 89.95
SOURCES
AirFlow Research (AFR)
28611 W. Industry Dr.
Valencia
CA  91355
Holley Performance Products
1801 Russellville Rd.
Bowling Green, KY 42101
KY  42101
270-782-2900
www.holley.com
ATI Performance Products
800-284-3433
www.atiperformanceproducts.com
Mahle/Clevite (Victor-Reinz)
Ann Arbor
MI
Autolite/Honeywell
Danbury
CT
Milodon
2250 Agate Ct.
Simi Valley
CA  93065
805-577-5950
www.milodon.net
Automotive Racing Products (ARP)
531 Spectrum Circle
Oxnard
CA  93030
805-278-7223
Scat Enterprises
3-10/-370-5501
scatenterprises.com
Autotronic Controls Corp. (MSD)
El Paso
TX
9-15/-857-5200
msdignition.com
Trick Flow Specialties (TFS)
1248 Southeast Ave.
Tallmadge
OH  44278
COMP Cams Wilson Manifolds
4700 NE 11th Ave.
Ft. Lauderdale
FL  33334
954-771-6216
www.wilsonmanifolds.com
Edelbrock
Dept. 5.0
2700 California St.
Torrance
CA  90503
310-781-2222
www.edelbrock.com
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