Bolt On 230+ HP to a Motorhome 454CI Big-Block
We bolt on Trick Flow top-end kit and find over 230 horsepower hiding in the crusty engine
Hot rodding is a hobby—not a career—for the vast majority of us. We drool over billet, but settle for cast, and we pinch pennies to eke the most out of our performance purchases. Horsepower per dollar is worth its weight in gold, and with this 87-octane-compatible, 567-hp barnstormer of a build, welcome to El Dorado.
It all started when Car Craft friend Curtis Mowery inherited a 1986 Suncrest Motorhome. The interior was decrepit, and the external fiberglass paneling was cracked and rotting. The engine, however—a 454-cu in. Mark IV big-block Chevy-was healthy and showed only 35,000 miles on the clock. Behind it was a TH400 that had been treated to a recent rebuild. As a whole, the RV was an ungainly eyesore. Under the skin, it was a perfect drivetrain donor.
Although vehicles of this stature aren't the most common—or practical—platforms out there, including Ford, Chevy, and Dodge all offered big-blocks for motorhome service. We have seen several make appearances at junkyards over the years, though they present a much more challenging engine-pull scenario, which we'll attest to firsthand.
Knowing the RV was a lost cause from the get-go, no time was wasted being gentle pulling the engine. Sawzalls buzzed, pry bars levered, and cutting-torch flames licked away obstacles. Soon the grease ball of a big-block was out and headed to Westech for a dyno and some mandatory speed parts. Afterward, it would find a new home between the fenders of a 1962 GMC truck project.
At the Dyno
Smog-era big-blocks get a bad rap. Their sub-8.0:1 compression rations, tiny cylinder-head ports, and anemic camshaft grinds are the main culprits. But what would the 31-year-old engine crank out on the engine dyno? Although it had a relatively conservative odometer reading of 35,000, lugging around a multi-ton motorhome isn't an easy life.
Westech's Troy Goldie buckled the big-block into the dyno cell, and Steve Brul worked the throttle for the first pull. Through the stock Quadrajet carburetor and a set of uncorked dyno headers, the engine delivered an oddly quiet 335 hp and whopping 485 lb-ft of torque. It was definitely healthy and far livelier than expected.
But who can leave well enough alone? The goal wasn't simply to validate a stock RV engine, but to see what kind of grunt was locked inside those 454 cubic inches by installing a better-breathing top end. To accomplish that goal, we turned to Trick Flow Specialties for one of its complete top-end kits (PN: TFS-K413-580-560). The kit included gaskets, valvetrain and camshaft, fasteners, and a set of PowerOval 280 as-cast cylinder heads. The kit bottom-lined at $3,499.97 on Summit Racing. That is certainly a significant amount of coin, but it's feasible for most gearheads with a project-car piggy bank—or during tax return season. The only thing not included in the kit was an intake and carburetor, so we ordered a Professional Products single-plane (PN 53037) from Summit Racing for the price of $209.97. Brul did note that a dual-plane intake would have likely provided more torque down low without giving up much on the top end due to the engine's planned conservative redline.
The old top end was unceremoniously yanked from the virgin motor, revealing carbon-coated but undamaged pistons. We cleaned the deck surfaces and laid fresh Felpro gaskets in place. The Trick Flow heads were installed with included ARP head bolts. This kit utilized a roller cam ground with 236 degrees of intake duration and 242 of exhaust duration as measured at 0.050-inch tappet lift. The lobe-separation angle was cut at 112 degrees and valve lift measured 0.600 inch on the intake and exhaust.
Because this engine was not equipped with a cam-stopper plate (as some later big-blocks are), it was necessary to control camshaft endplay. Brul grabbed a roller thrust bearing from Westech's parts stores and installed the camshaft, timing chain and sprocket, lifters, and the remainder of the valvetrain. The intake was then bolted in place and the factory HEI distributor was reused. We opted to borrow one of Westech's Holley Ultra HP carbs because of the tuning parts on hand, but in theory, the Quadrajet, with its 800-plus cfm, could've been reused.
With the engine buttoned up, it spun the dyno once more, recording 560 hp and 530 lb-ft of torque—a 225 hp improvement over stock! Is a head and cam swap a bolt-on affair? We'll gladly stand on our soapbox and say yes! On a pushrod engine, the job can easily be accomplished in a day, requiring no specialized tools and with no need to pull the engine from the car—sounds like a bolt-on to us. Thrilled to have bolted 200-plus horsepower onto an otherwise-stock RV engine, we began to ponder where else power was hidden. After some quick math, it was determined the engine only had an 8.2:1 compression ratio—as pump-gas friendly as compression ratios come. So to verify the affliction for cheap gas, we purged the dyno tank, refilling it with run-of-the-mill 87-octane from a local station. If detonation were to occur, the dyno would show a reduction in power and torque. Instead, it showed a 7-hp increase and 5-lb-ft rise in torque. This was a legitimate pump-gas big-block—for a total of $3,709.94. Next time you're perusing the local boneyard, give that monstrous motorhome a second look.
Holley; 1.866/464.655; Holley.com
Professional Products; 323/306-5067; Professional-Products.com
Summit Racing; 800/230-3030; SummitRacing.com
Trick Flow Specialties; 888/841-6556; TrickFlow.com
Westech Performance; 951/685-4767; WestechPerformance.com