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.
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.
Description PN Source priceCast steel 4.210 stroke crank RRE4210C RRE $500.00I-beam forged rods CR455 RRE 350.00Edelbrock RPM intake 7156 RRE 185.00Edelbrock ported RPM heads 60569 RRE 2,500.00ARP two-bolt main stud kit 194-5401 RRE 95.00Harland Sharp 1.5 full roller rockers 6001 RRE 230.00Comp Cams roller tip 1.52 1451-16 RRE 150.00Speed Demon 750 1402010 RRE 439.99Speed Demon 850 1563010 RRE 439.99CP pistons, custom RREcp455 RRE 595.00Cam ground by Comp Cams 51-000-S RRE 265.00
Pontiacengines.com; Grand Terrace, CA;909/370-0389; pontiacengines.com