Modified Mustangs & Fords
460 Big Block - Colossal Kaase Combo
Our Large and In Charge Big-Block Dyno Mule Returns
OK, we know it has been more than a year but we finally got around to Part 3 of Large and In Charge. Those with better-than-average memories will recall that we started out on this adventure with a stock 460 Ford (circa 1968) pulled from a wrecking yard. Step-by-step the big-block was upgraded with an intake and carb, roller rockers, mildly ported stock heads, and a small performance cam. The upgrades we showed you in the first part (May '11) pushed the power output from 349 hp and 492 lb-ft of torque to 437 hp and 507 lb-ft of torque. Part 2 stepped things up even further, with forged flat-top pistons, fully ported heads from MPG Heads and a custom solid flat-tappet cam from Cam Research Corp. These upgrades (June '11) combined with a single-plane intake and Holley carb allowed the 0.060-over 460 to exceed 600 hp, with peak numbers of 609 hp and 557 lb-ft of torque. This was a stout 460 to be sure, especially when you consider the use of iron heads, but we knew there was more power lurking within the 460 just waiting to be unleashed.
As big-blocks go, the factory 460 Ford was already sporting some impressive displacement, easily eclipsing the 440 Dodge, the 454 Chevy, and the 455 Buick and Pontiac offerings--only the massive 472- and 500-inch Cadillac engines offered more displacement. The stock displacement on the 460 came courtesy of a 4.36-inch bore combined with a 3.85-inch stroke. Though the big-bore combination suggested a candidate for high-rpm use (even more so for the smaller 429 with the 3.59 stroke), the 460 was primarily used by Ford for low-rpm towing and heavy hauling applications.
As big as the 460 is in stock configuration, the best way to improve the power (and more importantly torque) output is to make it even bigger. A little math here goes a long way toward explaining the benefit of the extra inches. Suppose we choose a power output for our racy 460 of 800 horsepower. Producing 800 hp from a 460 equates to a specific output of 1.739 hp per cubic inch, about the equivalent of a 525hp 302. Reaching this specific output with the 460 would be difficult, but not impossible. It would, however, require a whole slew of expensive components designed to allow the race engine to rev to the moon to achieve the elevated specific output. The downside of an elevated specific output is that the combination of compression, cam timing and head flow would certainly decrease driveability (an 800hp 460 would definitely be considered a race-only engine). Simply put, the smaller the engine, the wilder the combination required to reach a given power output.
One way around the driveability (or race-only) issue is to increase displacement. Increasing the displacement reduces the specific output required to reach a given power output. If we retain our goal of 800 hp but increase the displacement of our engine to 557 ci, we see that we have reduced the specific output to just 1.436 hp per cubic inch (the equivalent of a 433hp 302). It is not only much easier to produce 800 hp using a 557 than a 460, but the resulting combination will offer improved torque production, driveability, and engine life owed to the decrease in operating speed. An 800hp 460 will likely make peak power at or near 7,800 rpm, while the same power output from this 557 came at just 6,800 rpm. The 557-inch stroker kit will not cost any more (and likely less) than the rotating assembly required for building a dedicated 800hp 460 motor, but it will be more than pulling a used 460 from the wrecking yard.
Our 557-inch stroker kit came courtesy of L&R Automotive and included a 4.5-inch steel crank combined with a set of 6.70-inch, forged steel, H-beam rods from Procomp Electronics. The 4340 forged-steel crank and rods were originally teamed with a set of forged flat-top pistons from Probe Racing. We had a major oiling system failure on our first attempt and the high-compression pistons were replaced with a set of dished pistons to reduce the static compression ratio to a streetable 10.7:1. Different bore sizes are available, but this particular build up featured an increase in bore size from 4.36 inches to 4.44 inches (0.080 over). When combined with a jump in stroke from 3.85 inches to 4.5 inches, the result was an increase of nearly 100 ci (to 557 cubes). Obviously, making 800 hp with a 557-inch engine is much easier than producing the same output with a smaller 460-inch combo, but the big Ford required more than displacement to eclipse the 800hp mark. What the stroker needed was the ideal combination of what we like to call "the big three," or more specifically the heads, cam and intake manifold.
The displacement obviously plays a major part in the power production, but ultimate power production and even the shape of the entire curve are primarily dictated by your choice of the heads, cam and intake. The heads must flow enough to support the intended power level, while the cam and intake must be chosen to operate effectively at the intended rpm range. Teaming stock heads with a high-rpm single-plane intake and (long duration) solid roller cam would result in a less than desirable power level. The same goes for fully ported race heads, a stock cam and a two-barrel intake. Every component of the big three must be matched to optimize power production in the desired rpm range to maximize power production. Knowing that our goal of 800 hp would come to the high side of 6,500 rpm, we combined the Kaase P51 heads with a single-plane intake and healthy roller cam. All three of these would offer a sizable step up in performance compared to the components used in parts one and two on the smaller 460.
Jon Kaase knows a thing or two about Ford performance and his P51 heads are proof of that. The P51 heads offered flow numbers only dreamed about by fully ported stock, Cobra Jet, or even Super Cobra Jet heads. The aluminum construction was the first major step up compared to the ported iron heads used previously, but the differences didn't stop there. The P51 heads featured 310cc intake ports combined with 2.25-inch valves that flowed near 400 cfm (our testing indicated 391 cfm at 0.800 lift). The 145cc exhaust ports featured 1.760-inch valves and checked in at 248 cfm. The revised valve locations featured an 8.3-degree intake valve and 4.7-degree cant combined with a 4.0-degree exhaust valve angle and 3.2-degree cant. To further improve valve geometry, the P51 heads featured 0.100-inch-longer valves and 11/32-inch valve guides. The combustion chambers checked in at 72 cc's, meaning there was plenty of compression to be had with flat-top pistons on a typical 460, and why we had to resort to a 33cc dish on our 557 stroker to come in under 11.0:1.
With plenty of head flow, we took a hard look at the cam and intake. The intended power level required plenty of camshaft so we turned to Crane Cams for one of its powerful roller profiles. The cam (PN 358211) featured a healthy 0.742/0.718 lift split, a 264/278 duration split, and 112-degree LSA. The cam was teamed with Crane's 35570-16 lifters, 35975 timing chain and 1.73 ratio Gold Race rockers. Crane also supplied the necessary hardened pushrods for our stroker. The cam was combined with a single-plane intake from Ford Racing designed to accept a massive 4500-series Holley carburetor. We chose to top the intake with a new 1050 Ultra Dominator from Holley. Additional components employed on the stroker included a Ford distributor, Hooker headers and Meziere electric water pump. We originally intended to upgrade the oiling system, but the dyno schedule mandated that we get by with the stock pan and pick up. The completed engine was run through a pair of break-in procedures using Lucas break-in oil before subjecting it to full-throttle power runs. After dialing in the carb, performing a timing sweep and lash loop, the Kaase combo more than reached our goal. Let's see how it faired.