Building An Affordable Big Block Chevy Engine - Budget Rat

How to Build an Affordable Big-Block Chevy Engine

Tony Nausieda Aug 1, 2006 0 Comment(s)

Putting It Together
Don't be afraid to assemble the short-block yourself if you've got access to the proper tools and a clean workspace. From cheapest to costliest, you'll need a piston ring expander, engine-cleaning brushes, Simple Green, a dead-blow, plastic-face hammer, and a tapered ring compressor. Optional are ARP's trick aluminum-rod bolt protectors.

Before you clean the bare block, do yourself a favor and run ARP's thread chasing taps through all the holes, espe-cially those that restrain the cylinder heads and are often corroded and packed with dried-out sealant. This step is required for accurate torque readings when you're reassembling the motor. In our case, we cleaned every accessible oil passage in the block using Milodon engine brushes saturated with Simple Green, then blew the passages dry with compressed air. We wiped each bore with a series of ATF-soaked paper towels. Now that the block was really clean, we painted it and began assembly. We used proven Federal-Mogul pregapped moly piston rings and Com-petition-series bearings, which are high-quality and reasonably priced. ARP studs replaced the factory bolts, ensuring the caps stay put and allowing the Milodon louvered windage tray to bolt up. No, we didn't check the alignment of the main saddles after installing ARP's studs--although you probably ought to--but since the crank spun nicely after installation we figured the caps had to be close enough.

Coating each bearing shell and journal with STP helped prime the oil system and guard against galling. We lubed other metal-on-metal sliding surfaces (pistons, rings, and cylinder walls) with 20W-50 oil. Possibly the most critical metal-on-metal contact is the cam lobe and lifter interface, and we used two blister-packs of Crane's gray moly assembly lube on these areas. Before you bolt the heads onto the motor, have a close look at those stock head bolts and decide if you really want to reuse them. We didn't, so we picked up Milodon's engine fastener kit, which includes an assortment of engine bolts and studs, as well as the company's trick head bolts featuring stronger, rolled threads. The entire bolt kit costs less than most quality aftermarket head bolts alone, so it's still appropriate for a budget build. Before we installed the intake and carb, the Holley vacuum-secondary pod was swapped for its ingenious quick-change kit. The quick conversion makes spring changes a simple two-minute affair, perfect for tweaking at the track.

Alive!
Once the 454 was buttoned up in our '69, we used a homemade oil primer to spin the pump until oil flowed from each rocker arm. BBCs have an oft-noted reputation for cam destruction during the critical break-in time, so it's important to make sure all the oil passages are flowing properly before the combustion starts. To ensure minimal cranking time, fill each of the Holley's float bowls by carefully pouring fuel into each vent tube until it flows from the sight plug. Leave the thermostat out to prevent overheating, and it won't hurt to direct a large household fan into the grille area to initiate airflow through the radiator. Our motor fired right up with 80 psi of oil pressure--just the way we like it--and after checking the timing, we ran it at 2,000-2,200 rpm for 20 minutes. If your headers start to glow a dull red, add a little more ignition lead and check the idle mixture screws. After break-in, we backed down the idle to 750 rpm, where we observed 17 in/Hg of vacuum. Running the car at the track sounded like a lot more fun than strapping it to a chassis dyno, so we don't have real power numbers to post. But given our 106-mph quarter-mile, we think it's delivering around 335 hp to the rear wheels, which should put us solidly in the 12s...eventually.

Track Proven
Halfway through this story, your author relocated to Detroit, where there lies one giant obstacle to street machining: winter. We'd planned to go through the front sus-pension and install slapper bars on the rear, but instead rushed to the track armed only with a pair of 27x10.50 M/T ET Streets and a tired 36-year-old chassis. Wheel hop plagued our 60-foot times and some throttle lift was needed to keep the car straight through the quarter. The good news? This combo still trapped at 106 mph with no changes--jetting, timing, or otherwise, and we drove it 60 miles home after topping off the tank with a few gallons of 93. It's not the fastest and it's certainly not the prettiest, but we're hoping to address the former concern with a few low-buck chassis mods spread out over the long winter months. Pretty can wait.

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As installed, our stock piston/rod combo measured 0.015 inch below the deck--not great for quench, but typical for a stock GM-delivered configuration.

Before the Crane dual valvesprings were installed, we lubricated the guides with red assembly lube and pressed the Teflon valve seals over the guides using a deep-well socket. Ask your machine shop for a few extra seals--they're easy to mangle.

For proper installed torque, we coated the under-side of each Milodon head bolt with assembly lube. ARP offers a proper lube for fastener assembly, but conventional moly lube will suffice. Don't forget to coat the threads with a Teflon pipe sealant to prevent coolant from seeping to the surface.

We slathered the Powermax cam with Crane's assembly lube before stabbing it into the block. A quality Crane double-roller timing chain tied it all together.

On the top end, Crane's 3/8-inch one-piece push-rods and long-slot rocker arms comprise the remainder of the valvetrain. Given our conservative choice of cam grind, 110-pound seat pressure, and quality American-made parts, valvetrain durability should rival a factory install.

ARP main studs are admitted overkill for this motor, allowing a two-bolt block to withstand 500-plus horsepower. The textbook Milodon oiling system consists of a high-volume pump and hardened steel drive, plus a low-restriction pickup coupled with an 8-quart pan and windage tray. Together it delivers no less than 30 psi at idle and 70 psi at speed. Most importantly, we observed no appreciable pressure drop during a quarter-mile pass.

Much of our budget was wisely spent on the Holley 850-cfm carb and World Products dual-plane intake, buttoned up with Fel-Pro's composite gaskets. A set of Trans-Dapt valve covers (powdercoated Chevy Orange) lend a period look--and actually fit properly without leaking.

Quick Notes
Combo
A freshened 454 dropped into one '69 RS/SS
Bottom Line
We didn't break the bank and it hit bottom 13s in the quarter-mile.
Price (approx)
$2,500

454 CAMARO PERFORMANCE
Best e.t.:
13.16 at 105.7, 2.17 60-foot
Best mph:
13.39 at 106.1, 2.23 60-foot
Idle vacuum:
17 in-Hg at 750 rpm (in Neutral)
Average fuel economy:
11 mpg (street and race use)

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