Proven Horsepower Engine Combinations - 500hp Engine Combos

Small-Block Ford 408ci
We've seen naturally aspirated 500hp 302s, and they're rowdy and right on the verge of disaster. On the other hand, the 351 Windsor-based engine that came in fullsize cars and trucks from 1969 all the way to about 2003 has the displacement for good torque and with the right combination of parts can make an easy streetable 520 hp.

Wow, that looks pricey.

The guys at Coast High Performance build Windsor-based 408s with 4.00-inch strokes and 4.030 bores using tall-deck 351s and 6.2-inch rods. The preferred block is from the Ford Lightning truck that has a factory roller cam already installed, but short of that, the '82-and-later block has the one-piece rear main seal, and you can buy a roller-cam retrofit kit with a small base circle so the lifters will clear the dog bones. Then you just drill and tap for the lifter galley spider. All the blocks require clearancing for the rod bolts when using the stroker crank, and Coast suggests using a main girdle for combinations approaching 500 hp and engine speeds nearing 7,000 rpm. For only $169, the girdle is cheap insurance. Another trick is finding a '69-'70 block that has thicker cylinder walls and will take a 0.060 bore for a rebuild later. You can also step up to a Ford Motorsports block for another $1,000 to get the thick walls, one-piece rear main seal, and roller cam in one package.

The cam choice is the Crane 248/256 at 0.050 duration hydraulic roller with 0.595/0.605 lift ground on a 110 lobe center. It may sound a little radical, but at 408 inches, Coast reports it is actually very docile and driveable. Coast uses the AFR 205 street/strip heads that flow 306 cfm right around 0.600 lift. It can be used out of the box after you set the seat pressure to match the cam. For carbureted applications, Coast uses the Edelbrock Victor Jr. single-plane intake, Holley HP 750, and an engine compression ratio of 9.5:1. The fuel-injected applications get 10.0:1-10.5:1 because they usually have better fuel and timing control.

The 408 will fit in your Fox-body or Cobra kit car with a cowl hood, and there are off-the-shelf headers for '64-'66 Mustangs. The Fox engine mounts are the same for the 351 and the 302, you'll just have to use a Fox oil pan.

Using 1 3/4 long-tube headers, this combination should make 520 at 6,300 rpm, which is the limit of the lifters, and 490 lb-ft at 4,200 rpm. The typical Fox-body will be around 3,200 pounds with a five-speed, and a 3.73 gear will give you mid-11s at 120 mph.

Coast High Performance
Torrance, CA
310/784-1010
www.coasthigh.com

Pontiac 455ci
At 4.210 inches, the Pontiac 455 has one of the largest factory strokes available. The bad news is that you just don't see them laying around like you used to. Instead, Bruce Fulper at PontiacEngines.com (aka Rock 'n' Roll Engineering) showed us that the easiest way to build a 455 is to buy any '67-'75 400 block and use a 455 crank. Fulper has experimented and says the two-bolt block will live up to 900 hp with proper care and a main stud kit. The '76-'79 blocks have thinner main webs and should be avoided for anything other than a mild street build.

If you do not have a stock 455 crank and block, a 4.210-inch-stroke aftermarket crank is available in two main diameters. Stock, which is 3.250 inches and will fit a 421, 428, or 455 block, or a 3.00-inch-diameter that will fit into a 326, 350, 389, or 400 block. These cranks inspected and balanced are only about $500. When using a 3.00-inch-main 455 crank, you will need to grind 0.100 off the block in the area where the front counterweight touches.

Fulper warns against using an aftermarket crank assembly that uses a 4.250 stroke but comes with a heavier 6.800 rod length for this combination. The Pontiac's stock rod length is 6.625 and in his opinion it's already too long. Moving from a 4.210 to a 4.250 only adds 0.040 to the stroke, which isn't enough to measure on a dyno. Retaining the stock-length rods and stroke makes replacing parts easier with the added benefit of a lighter rotating assembly for less money. Fulper recommends forged I-beam rods with ARP bolts.

We ran across two Pontiac 400s in the wrecking yard. Even the early ones are still out there.

We ran across two Pontiac 400s in the wrecking yard. Even the early ones are still out the

The large bore and stroke can make a lot of torque, even with stock cast-iron heads, but even using ported cast-iron heads, it takes a large roller cam to make 500 hp. So the horsepower is limited by the head selection. The secret to Fulper's low-rpm power is in his ported Edelbrock castings. He buys them bare, ports them, and assembles them with some finish work on the valve angles and matching valve springs. The heads are priced at about $800 more than the complete unported version, but because the aftermarket crank is inexpensive and you don't need an aftermarket block, you can spend the money on head work instead.

Fulper also says the large dual-plane Edelbrock RPM intake manifold can feed an 800-horse 455 with a 150-shot of nitrous. You can use it unported, as the runner volumes are already large enough for the job.

For the cam, Fulper recommends the least expensive route using a custom solid flat-tappet grind with hydraulic lifters. Only certain grinds can do this, so don't try ordering a different profile without consulting Fulper or Dean Harvey at Comp Cams, who also worked on this combo. A recent 455 build using this cam made 500 hp at 4,800 rpm and more importantly 558 lb-ft at 3,000 rpm. With the right street converter, this combo will push any 3,500-pound car into the mid-11s and do it with a 3:55 gear. Here are the specs: Intake opens 10 degrees BTDC and closes at 46 degrees ABDC. Exhaust opens 56 degrees BBDC and closes 4 degrees ATDC. The duration is 236/240 at 0.050 on a 112 lobe separation angle installed on a 108. Fulper uses Harland Sharp 1.5 rockers for $225 a set or the more budget-minded Comp Cams 1.52 ratio roller-tip rockers.

Pontiacengines.com
Grand Terrace, CA
909/370-0389
pontiacengines.com

By Douglas R. Glad

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