454 Engine - How To Build An Affordable Big-Block Budget Rat

A trick set of BBC aftermarket heads and a quality rod/piston combination will easily approach three grand. It's numbers like this that send guys running back to the small-block camp, but there's an alternative: Save a ton of green by starting with a good core motor. The better the core, the more stock parts you can recondition-and most of the stock BBC equipment will suffice nicely for a naturally aspirated street mill. The concept with this build is to disassemble, clean, and recondition as many stock parts as possible and use affordable, proven aftermarket parts when the stock ones truly compromise our goal of high performance. Our strategy here is exactly what most of you set out to do: build a reliable combination decent enough to turn respectable times at the track-without requiring a vacuum canister, a car trailer, or a second mortgage.

The Right Core
To keep things on the cheap, we found a 454 that didn't need to be bored; in fact, it still held the original standard-bore cast pistons with discernable cross-hatching on the cylinder walls. Even better, the stamped suffix ID'd it as a '70 390-horse variant out of a Caprice, otherwise known as an RPO LS5. Fitted with closed-chamber, oval-port heads, 10.25:1 compression, and a steel crank, it was well worth the $1,000 asking price, we figured. Days later the original intake, distributor, exhaust manifolds, and smog stuff netted an astounding $734 on eBay, slashing our initial investment to a laughable $266. Really. If you're having trouble locating a musclecar-era BBC, you can build the near-equivalent of this motor using a smog-era 454 Gen IV short-block and a set of closed-chamber, oval-port heads. Any of the large oval-port castings from '65 to '70 will have small, 98-101cc chambers to achieve approximately 9:1 compression with smog-era 454 pistons, and these heads are still quite plentiful and cheap.

Autopsy
With the engine apart, we found the crank had been cut 0.010 inch under on the mains and rods. Scarred main bearings and excessive wear on a few rod bearings told the story of a rebuild gone wrong. With parts in hand, we headed to the experts at Johnson Machine Service (JMS) in Monrovia, California, to formulate a game plan for reconditioning. Owner/operator Mike Johnson gave us mostly good news: The block, pistons, and crank were all usable, and the heads weren't cracked, although everything was a little tired. As expected, the big end of each rod was out-of-round and needed to be resized; one was replaced because it showed evidence of overheating. The JMS advantage became clear when Johnson plucked an identical specimen from a huge barrel of core BBC rods. Years of churning out high-performance big-blocks has created a huge stock of cores, so every-thing is available in-house if you'd rather not put forth the effort to search for the parts yourself.