You’ve got to love the Chevy big block for its raw ability to make aggressive amounts of bone-crushing torque without breaking a sweat. It also loves high-revving horsepower, giving you the best of both worlds.
Most of you who love the Bowtie understand the origins of Chevrolet’s powerful big blocks, which began in 1958 with the W-Series Mark I at 348ci, followed by the legendary 409 in 1961—and later the super rare RPO 427ci Z11 in 1963. (And, yes, you could actually order one from Chevrolet.)
There were also the Mark II
and Mark IIS “Mystery Motors” displacing 409ci and 427ci (the latter was the
only version actually raced). The Mark III would have been a Packard design and
tooling, however, GM said no to this one. It never got off the ground and
that’s okay with us.
Before you is Chevrolet’s Mark IV big block, which was introduced in 1965 with 396 cubic inches. There was also the lesser-known 366 back in the day, which was a low-revving truck engine designed to make good low-end torque. The 396 swiftly led to what already existed in terms of displacement—the 427, which led to the 402 and 454 in 1970.
At the cusp of the 1990s, GM not only changed the name “Mark” to “Generation,” it also changed the engine. The big block Chevy (BBC) became the Generation V big block. The block got a one-piece rear main seal for leak prevention. Four-bolt main caps became standard on all one-piece rear main seal 1991-up blocks, and that’s okay with us too. The oiling system changed significantly for the better. GM changed the valvetrain from stamped steel rockers, to non-adjustable aluminum. There were also significant improvements to the block.
The lower displacement 366ci truck engine became the 6.0L. The 454 stayed. GM added the 502/8.2L and 572/9.4L to its aftermarket performance parts division, producing a new family of power stump pullers.
Making Affordable Big Block Chevy Power
The big block Chevy has always been about great low- and mid-range torque—real street power where you need it for the freeway and for the traffic light. However, the BBC can also make high-rpm horsepower for the drag strip. But you don’t have to take this engine to 7,000 rpm to make real power. You can drop it into a classic Chevelle or a C-Series pick-up and scorch the earth at 5,000 rpm.
It is so easy to make power with this engine. We’re with internal combustion technician Jeff Latimer in Los Angeles, California, building more Chevy iron like we’ve always done with this guy. Jeff’s going to show you how to make plenty of torque without selling off the farm.
“I built this engine for a good friend of mine. This was a junkyard engine and he had only cleaned and painted it with a new intake, timing set, and oil pump.” Jeff goes on to say, “He’s putting it in a body-off full-scale restoration on a 1967 El Camino. I felt his El Camino deserved better. I grabbed this engine and hauled it back to my shop.”
Jeff found a lot of problems
as he was tearing the engine apart. It had badly blown head gaskets. It was a
1980s vintage 454ci truck big-block with small port heads. It was never going
to impress anyone the way it was. “I was able to source a pair of 1973 vintage
large oval-port performance cylinder heads for this effort. The heads were
rebuilt using Manley stainless steel valves to eliminate the expense of
hardened exhaust valve seats. They were also machined and assembled with new Howard
valve springs and Viton valve seals.”
Down below, Jeff opted for a good flat tappet hydraulic cam from Howard’s Cams along with GM lifters, which Jeff feels are the best choice. “I used genuine GM hydraulic lifters because they are in my opinion the only ones to use on a Chevy with a flat tappet cam. They have a separate hardened face at the base of the lifter.”
“A big block Chevy with a 1.7:1 rocker ratio is one of the engines that could have the cam go flat during break-in. I opted for better quality OEM and aftermarket parts.” He went on to tell us the stock 1.7:1 stock rocker ratio worked just fine with the grooved rocker fulcrum balls for durability. Stock pushrods were also cleaned and reused in the interest of saving money.
Jeff added the block was thermal cleaned and magnafluxed at JGM Performance Engineering, then, bored and honed for the Keith Black .030-inch over forged pistons with floating pins and 1/16 x 3/16-inch low friction rings. The block was also decked to achieve a tight quench.
Jeff tells us this is not a racing engine and shouldn’t be treated like one. It is built for cruising and brute acceleration for the freeway and open road. “It’s for cruising…” Jeff confirms. On JGM’s dyno, the 454 made 410 horsepower and 545 lbs.-ft. of torque. It did all of this at well under 6,000 rpm. What’s more, it will turn these numbers all day long on pump gas.
Chevrolet 454 Street Torque Recipe
1987 7.4L #14015445 Block
1973 #353049 Oval Port Head Castings (122cc chambers)
Before you can degree the cam, Jeff stresses you must first ascertain true top-dead-center (TDC) at #1 cylinder. He adds if this isn’t right, nothing else will be right in terms of cam timing. You’re going to need a dial indicator and a degree wheel along with a bridge-style mount in order to check true TDC.
Get the dial
indicator centered on the piston, with the piston at TDC.
Slowly crank the
engine until the piston reaches its maximum height—which can be above or below
Install a degree
wheel with a pointer attached to the block. Set the degree wheel at zero. Zero
the dial indicator.
Slowly crank the
engine backwards until the piston travels .050-inch downward. Note the
indication on the degree wheel.
Slowly turn the
crank back until the piston tops out and then descends in the bore .050-inch.
Note the number on the degree wheel.
If the degree wheel
reads the same on both sides of top-dead-center (TDC), you’ve found true TDC.
If the numbers do
not match, adjust the degree wheel until they do match.
“In reality, when I turn the engine backwards, I would likely go .100-inch down in the bore, then, turn it back until it read .050-inch,” Jeff tells us. He adds, “Determining true TDC is vital before degreeing the cam because all your numbers would be adversely affected by slack in the timing chain.” He goes on to say, “This is not necessary when checking TDC, but it is the only way to do it when checking camshaft numbers. It is always best to check true TDC while turning the crank in normal operating direction.”