Tech / Tech Articles

Budget Big Block Chevy Street Torque!

(Image/Jim Smart)

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.

“The engine was dyno’d for camshaft break-in with Driven BR30 oil, then, changed with Valvoline VR1 10w30 weight High Zinc oil, which is something you should do with any flat tappet camshaft in the interest of durability,” Jeff comments.

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

Our foundation for this BBC build is a 1987 vintage #14015445 454 block that has been precision machined by JGM Performance Engineering in Valencia, California. (Image/Jim Smart)
Here are all the goods for solid reliable Chevrolet power. A stock polished cast iron crank, Eagle I-beam rods, KB hypereutectic pistons, and a host of Summit Racing parts within. Jeff was able to get it all from Summit Racing. What’s more, this classic big block doesn’t have to be old school either. You can top this guy with carburetion or electronic fuel injection. (Image/Jim Smart)
We like these traditional #353049 big-Chevy heads with their 122cc chambers, 2.065/1.725-inch stainless valves, and 255/119cc volume intake/exhaust ports. No port work done here because it is unnecessary. This guy will make a tremendous amount of power without going much over 5,000 rpm. (Image/Jim Smart)
Jeff’s running a Howard’s Cams flat tappet cam (#12002112) with 112° LSA and GM hydraulic lifters for durability. This cam promises plenty of low-end torque and comes on strong at high rpm. Jeff uses moly lube on the cam lobes and engine assembly lube on the journals. He used a good break-in oil with plenty of zinc for the initial fire-up. (Image/Jim Smart)
We’ve worked with engine builders who suggest staggering the rear main seal ends with two-piece rear mains to prevent leaks. Jeff tells us you run the risk of having the seal halves bunch up and distort at the ends that way. He suggests having the seal ends end-to-end where the #5 main cap meets the block and using a daub of Permatex Right Stuff Gasket Maker at the seal ends. You also want to apply a thin layer of sealer between the cap and block. (Image/Jim Smart)
Jeff demonstrates his approach to rear main seal installation, with seal ends positioned at the cap and block contact points. The seal lip must be pointed toward the crank. Crankcase pressure leans on the seal lip to further secure the seal and prevent leaks. Sealer must also be applied between the cap and block. (Image/Jim Smart)
Crankshaft endplay is checked, which should be .004- to .008-inch. (Image/Jim Smart)
Jeff opted for a stock timing set. There wasn’t the need for a dual-roller. Chevrolet tells us to get the cam and crank sprockets with the timing marks together—12 o’clock at the crank and six o’clock at the cam sprocket. True accuracy comes when we check for true top-dead-center and degree the cam. These timing marks are a starting point. (Image/Jim Smart)
Budget doesn’t have to mean cheap. Jeff opted for durability with Keith Black hypereutectic pistons with coated skirts for reduced friction along with Eagle rods, which involved less expense than if he would have had the rods reconditioned and fitted with new ARP bolts. This is money well spent in the long run for durability. (Image/Jim Smart)
Jeff pushes the issue of cleanliness because even the most finite elements can harm an engine. I’ve learned from other builders that even simple house dust will score bearings and cylinder walls. Here, Jeff does a thorough wipedown with a tack cloth and Akerly & Childs ring lube until cylinder walls come clean and are lubed. (Image/Jim Smart)
Jeff maintains a battery of more common sized billet piston ring compressors. This makes quick work of engine assembly. The ring compressor and piston are generously bathed with ring lube for ease of installation. (Image/Jim Smart)
Rod bolts are hand-snugged, then, torqued to specifications. Jeff has chosen Clevite CLE-CB-743P rod bearings for this street 454. (Image/Jim Smart)
Jeff has chosen Eagle #SIR-6135B I-Beam connecting rods, which are optimum for this particular 454. These new Eagle rods cost about the same as reconditioning the 454’s factory rods and you wind up with a better rod. These are great rods for the money. (Image/Jim Smart)
Eagle connecting rod bolt threads are moly lubed, then torqued to 63 ft.-lbs. in one-third values, then, rechecked. (Image/Jim Smart)

Getting True Top-Dead-Center

(Image/Jim Smart)

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 deck.
  • 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.”

Every camshaft should be degreed to accurately determine valve timing events and how they relate to the manufacturer’s cam card. Rare is the production camshaft that is spot on per the cam card. Once you understand actual cam timing events, it becomes easier to determine what needs to happen next. (Image/Jim Smart)
Jeff is using Dorman cylinder head bolts from Summit Racing. These bolts are wet-deck ready with Teflon on the bolt threads. Cylinder head bolt torque is 75 ft.-lbs. long bolts and 65 ft.-lbs. for the short ones tightened in proper sequence using sealer on the threads. Torque them in one-third values, then, recheck final torque. (Image/Jim Smart)
Time proven Fel-Pro cylinder head gaskets are a brand we look to time and time again because we don’t want the disappointment of leaks. Jeff has checked contact surfaces for cleanliness. He has applied Permatex “The Right Stuff” gasket maker to the corners (arrows), which tend to leak if assembled unprotected. (Image/Jim Smart)
These 1973-vintage 454 cylinder heads have the 122cc chambers, which is what you want for your 454 project. We have 8.8:1 compression. Chambers became larger in the mid-1970s, which means a greater loss of compression. The quickest path to power is compression. (Image/Jim Smart)
Cylinder heads are seated at this time. Install all bolts and hand snug for security. (Image/Jim Smart)
Jeff lubricates bolt/washer contact surfaces to ensure honest torque readings. Never tighten bolts dry. (Image/Jim Smart)
There’s a lot to be learned about applying fastener torque. Never jerk a torque wrench to get the click. Apply nice smooth torque to the fastener and do it in one-third values. Again, once all fasteners are torqued, go back and check torque readings. (Image/Jim Smart)
Jeff stresses the use of genuine GM tappets if you’re opting for a flat-tappet camshaft. Apply moly lube to the lifter contact surface and fill the pan with a zinc additive engine oil when the time comes to fire the engine. GM lifters have a hardened base, which can handle the torture of a rough ride over the cam lobe. Roller tappet engines do not require moly lube or zinc. (Image/Jim Smart)

We’ve opted for stock GM valvetrain components. Before you here is a ball-type pushrod, which is fine if you’re on a tight budget. Stamped steel 1.7:1 GM rockers will be adequate for what our 454 is expected to do. (Image/Jim Smart)
Screw-in rocker arm studs and guide plates will keep pushrods centered and in perfect alignment. (Image/Jim Smart)
Jeff stresses the use of the right lubricants during assembly. Cam lobes and lifter contact surfaces get moly lube (molybdenum grease) for proper break-in and work-hardening of cam lobes and lifters. Lifter bores and pushrod tips get engine assembly lube. (Image/Jim Smart)
Valve adjustment is best taken one cylinder at a time. Take valve adjustment one cylinder, one bank at a time. Slowly crank the engine. As the intake valve is closing, adjust the exhaust valve. As the exhaust valve is opening, adjust the intake valve. For mechanical lifters, use a thickness gauge. With hydraulic lifters, slowly tighten the rocker arm adjustment until you can feel a slight preload at the pushrod. The rocker arm adjustment can be anywhere from zero lash to a half-turn. For racing, zero to an eighth-turn. For street, a quarter-turn. (Image/Jim Smart)
Because we want a good power band, Jeff suggested the Edelbrock Performer for big block Chevys. This is a nice dual-plane manifold, which is terrific for street and strip. It delivers great low- to mid-range torque while coming on strong at high rpm. It is all done around 5,500 rpm. The big block Chevy doesn’t have to rev sky-high to make abundant power, which is great for your Camaro, Nova, Chevelle, or C-Series truck. (Image/Jim Smart)
Although gasket sets include end gaskets, most of us never use them. Jeff applies a bead of Permatex’s The Right Stuff, which is the only sealer to use. He applies just enough to fill the gap between manifold and block, then, wipes the bead clean. (Image/Jim Smart)
Jeff uses modest amounts of Permatex The Right Stuff around cooling passages. (Image/Jim Smart)
It is a matter of personal choice whether you use the heat riser passage or not. Fel-Pro provides this reducer to limit exhaust heat to the intake manifold. You can completely block off the heat passage, which will help your intake manifold run cooler. (Image/Jim Smart)
Torqueing the intake manifold is not a task to be taken lightly. Once the manifold is seated, fasteners are snugged to get the manifold fully seated. Full torque is 25 ft.-lbs. with the bolts tightened in crisscross fashion. Once again in one-third values. Never over-torque intake manifold bolts. Check them twice once tight. (Image/Jim Smart)
Dyno time at JGM Performance Engineering netted 410 horsepower at 4,800 rpm and 545 lb.-ft. of torque at 3,400 rpm. Terrific low- to mid-range street torque. This works exceedingly well in both a C-Series pick-up or a classic Chevelle, Camaro, or Nova. You get good street power where you need it most without spending a fortune. (Image/Jim Smart)

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