Words And Photos: Richard Holdener

Back in Part 1 of our Junkyard Warriors saga, we pulled a pair of big blocks from the wrecking yard and subjected them to the dyno. The idea was to compare a stock 454 Chevy to a 460 Ford, the age-old Ford vs Chevy rivalry. Obviously there were a great many different Fords and great many different Chevys that fit the bill, but in the end, we chose a pair of comparable big blocks. No muscle-car engines here, our test motors came straight from the engine bays of work trucks.

The 1993 7.4L Chevy was originally sporting TBI fuel injection and came with power ratings of 230 hp and 385 lb-ft of torque. Similar in specs, the carbureted 1986 Ford 460 offered 245 hp and a Chevy-matching 385 lb-ft. The reason for choosing these combatants was a trio of price, availability, and potential. The motors were dirt cheap from the wrecking yard, there were plenty to choose from, and based on sheer displacement alone, they had a ton of power just begging to be unleashed.

Rather than throw the kitchen sink at them, we decided to demonstrate a few different levels, since readers will differ in their approach. For obvious reasons, big blocks are popular race motors, but they make excellent power plants for tow rigs as well. I mean, come on, they came from trucks to begin with! It is for this versatility that we designed the upgrades on our warriors.

First on this list was a cam upgrade, or more accurately a valvetrain upgrade. The wimpy, stock truck cam was obviously not intended for performance use, but the cam was just one part of the valvetrain equation. We enlisted COMP Cams, who supplied a complete K-Kit for each motor. To keep the competition even, both the 454 and 460 received the same (RV-ish) XE256H cam profile. Both big blocks featured factory hydraulic flat-tappet cams, so both received flat-tappet cam upgrades. We may perform a hydraulic-roller upgrade in the future, but for now we will stick with the tried-and-true (and less expensive) flat-tappet design.

Supplied by COMP cams, the K-Kit included not only the XE256 cam, but also new lifters, timing chain, valve springs, retainers, locks, seals, and even assembly lube. The Chevy version of the XE256H cam offered a .480/.485 lift split, a 212/218-degree duration split and 110-degree lsa. The Ford version differed only slightly in the lift, with a .487/.493 lift split, the same 212/218-degree duration split and 110-degree lsa.

To ensure proper break-in and a long life, we made sure to liberally coat the cam lobes and lifters with mold-based assembly lube then filled the crank case with COMP Cams Break-In Oil. Both cams were then treated to 25-minute break-in cycles to ensure the cam and lifters were properly acquainted before running the motors in anger. It was necessary to replace the factory valve springs with the upgrades supplied in the K-Kits, as the stock springs greatly limited rpm and cam lift potential. There is nothing worse than the sound of valve float on the dyno. The cam kits allowed the big blocks to rev cleanly past their respective power peaks.

As expected, the COMP cam offered plenty of extra power. The XE256H cam increased the power output of the Chevy from 334 hp and 448 lb-ft of torque to 381 hp and 484 lb-ft. The extra 47 hp and 36 lb-ft was welcome, but so too was the fact this cam offered more power everywhere, even down below 3,000 rpm. The cam increased the power output of the Ford 460 as well, from 299 hp and 339 lb-ft to 340 hp and an even 450 lb-ft of torque. The extra 41 hp demonstrated the value of the COMP Xtreme Energy cam, but something was still amiss with the Ford.

After running the 460 in Part 1, we suspected the difference in power between the Ford and Chevy was the use of an aftermarket Weiand Stealth intake on the Chevy (to replace the TBI). For this round, the Ford got a matching Stealth but still never managed to catch up to the power offered by 454. At least part of the culprit was revealed when we performed a leak down of both motors. The extra seven years of age, mileage and likely neglect had obviously taken it toll on the 460, as the leak down showed the 454 was sealed up tight as a drum. We will rectify this situation with a quick rebuild before Part 3, but look for higher compression, wilder cam timing, and even some fancy new head gear. Score to date: Chevy 2, Ford 0!

The mild XE256H cam offered impressive power gains, and the 911-16 spring kit allowed the Gen V BBC motor to rev to its full potential. The cam upgrade increased the power output from 334 hp and 458 lb-ft of torque to 381 hp and 484 lb-ft of torque. The cam upgrade even improved the power output below 3,000 rpm.

Like the Chevy, the XE256H cam upgrade improved the power output of the 460 substantially. The peak numbers jumped from 299 hp and 439 lb-ft of torque to 340 hp and 450 lb-ft of torque, but we expected more. Our hope was that the Weiand intake would put the Ford on par with the Chevy, but a leak down test of both motors showed that the extra seven years of age (and mileage) had taken its toll on the Ford.

Sources

COMP Cams
compcams.com

Holley/Hooker/Weiand
holley.com