It's good to know what you want when you set out to build an engine. It's even better to actually get it.

As Ken Sink formulated a replacement Rat motor for his original big-block-powered '68 Chevelle SS, he wanted two things: torque and fun. It's a concise set of goals, especially since in a street car, the two are synonymous. There's a sure way to achieve lots of fun-inducing grunt, and that's with a big bore and a long stroke. Accordingly, Sink turned to Speed-O-Motive to create a muscular yet very reasonable 9.4:1 540ci fat-block. The result is a powerplant that will tolerate any type of pump-gas swill, handle anything from around-town cruising to a cross-country journey, and make a grin-inducing 659 hp and 620 lb-ft of torque while doing it.

The basis for this big-block creation was a GM Gen VI block. This piece, which is the basis of GMPP's 502 crate motors, has a number of advantages when creating this type of big-bore, big-stroke combo. Right off the bat, it has four-bolt mains and will clear up to a 4.500-inch stroke. The Gen VI block also has Siamesed bores. Put simply, this means there is thicker wall material with no water jackets between the cylinders, allowing for bores as large as 4.500 inches in diameter.

Sink set out to make the combo bulletproof, teaming the four-bolt mains with a Speed-O-Motive forged steel crank, Carrillo forged H-beam rods, and JE forged flat-top pistons. The bore-by-stroke dimensions to create 540 ci are 4.500 by 4.250 inches. It's a good combination, simply because it has more of everything. More stroke equals more torque. Bigger bore equals more power. And with a 9.4:1 compression ratio, this thing will most likely even run on California 87-octane without complaining.

While a lower end certainly costs plenty of change, the single biggest investment a big-block builder will make is the cylinder heads. Sink chose a set of Brodix Race-Rite BB-R series lungs, and they proved to be ideally matched to the rest of the combo. These heads flow plenty, as you can see in the accompanying chart, but the 294cc intake ports also maintain good air speed, meaning torque levels and low-rpm throttle response are also good. The RRs also have their exhaust ports in the stock location, so header installation in the '68 Chevelle won't be a problem. They're also drilled to accept factory-style brackets, so outfitting the new engine with accessories will be problem-free as well. In fact, except for the fact that a Gen VI block has no provision for a mechanical fuel pump, Sink figures that no one looking under the hood will be able to tell the difference between the original Rat and his new 540 brute.

In accordance with the "able to be driven anywhere" ethos Sink followed for this engine, moderation was the name of the game when it came to the camshaft. A Comp solid roller got the nod, so occasional valve lash settings are really the only (small) hitch in this mule's leave-it-alone, plug-and-play guise. In our book, the cam plays to the strength of the heads with its 0.653/0.660-inch intake and exhaust lift figures. These specs take full advantage of the heads' excellent flow numbers, getting as much mixture into the cylinders are possible. On the other hand, the cam's 248/254-degree duration figures are fairly moderate. So while this engine definitely makes good horsepower (659 at 6,200 rpm), it has a very broad torque band, averaging 556 lb-ft from 3,200 to 6,500 rpm.

On the one hand, there's no doubt that this 540 combo could make loads more power. One indication of that is the massive 54 lb-ft average torque gain we saw by adding more intake plenum space with a 2-inch open spacer; this one's a no-brainer for this engine. The other indication is the moderate cam, creating a powerband that's done by 6,500 rpm. This thing could certainly make beaucoup horsepower with a more-aggressive 'stick. On the other hand, that would defeat the whole purpose of the thing. "I don't need a screamer," Sink explained. "This is kind of a reasonable motor to build, and the whole goal is just fun." Oh, and don't forget about the torque. With what this 540 has on hand, we don't think the fun part will be a problem.

Quick Notes
What We Did

Followed along as Speed-O-Motive built a serious street 540 big-block

Bottom Line
There's grunt to spare on tap, and plenty of horsepower to go with it.

Cost (Approx)
$13,000

WHAT'S IT FLOW?
BRODIX RR BB-R HEADS
Valve Size 0.200 0.300 0.400 0.500 0.600 0.650 0.700
2.250 intake 160 226 276 314 337 341 342
1.880 exhaust 116 145 172 196 217 230 236
CAM SPECS 540CI BUILDSHEET
Manufacturer Comp Cams Displacement 540 ci
PN 11-772-8 Bore x Stroke 4.500 x 4.250
Grind Number XR286R Compression 9.4:1
Type solid roller Rod Center-to-Center 6.385 inches
Valve Lift 0.653/0.660-inch, intake/exhaust Piston Deck Height 0.000
Duration at 0.050 248/254 degrees, intake/exhaust Chamber Volume 119 cc
Lash (hot) 0.016/0.018, intake/exhaust Rod Bearing Clearance 0.0025
Lobe Separation Angle 110 degrees Crank endplay 0.0075
  Piston Ring  
  Endgap 0.021 top, 0.018 second
  Main Bearing Cap Torque 100 ft-lbs (moly lube)
  Rod Bolt Torque 75 ft-lb (moly lube)
  Head Bolt Torque 70 ft-lb (moly lube)
PARTS LIST
MFG PN ITEM
ARP 135-3701 Head bolts
135-2001 Intake manifold bolts
100-7504 Valve cover bolts
200-2401 Carb bolts
Brodix RR BB-R Assembled rectangular-port cylinder heads
Carillo C-427>-76385H Forged H-beam rods
Comp Cams 1320-16 Pro Magnum roller rockers, 1.7:1 ratio
11-772-8 Solid roller cam
897-16 Solid roller lifters
Federal Mogul 1075 Head gaskets
1275 Intake gaskets
Z2920 One-piece main seal
GM Performance
Parts 10237292 Gen VI Block
Holley 80514-1 1000 HP carb, annular boosters
JE Pistons 257965 Flat-top pistons, -3.0 dome volume
Mahle Clevite MS 829 H Main bearings
  CB 743 H Rod bearings
Manley Performance
Products 25835-8 8.350-inch pushrods
25940-8 9.400-inch pushrods
42288 7/16-inch rocker studs
42164 pushrod guides
Milodon 84510 Balancer bolt
85680 Breather
22010 Dipstick
30955 Low-profile oil pan
81137 Main studs, with windage tray
41002 One-piece oil pan gasket
81151 Oil pan studs
18760 Oil pump
18201 Extreme-duty pick-up
14875 Timing cover
15055 Timing chain
85600 Valve covers
32200 Windage tray, louvered
MSD Ignition 95551 Pro Billet distributor
31379 Super Conductor wires
Professional Products 53030 Hurricane intake manifold, rectangular port
90005 PowerForce+Plus harmonic damper
Speed-O-Motive SOM-3-454B 4340 forged steel crank
Trans-Dapt 2461 2-inch plastic spacer
DYNO DETAILS 1
Headers Dawson 2 1/8-inch long tubes
Advance 36 degrees
Fuel 91-octane unleaded
Carb Holley HP 1000
Jets 84/88 with 6.5 power valve
Max Torque @ rpm 619 @ 4,600
Max Power @ rpm 645 @ 6,200
Avg Torque 512
Avg Power 346
DYNO DETAILS 2
Headers Dawson 2 1/8-inch long tubes
Advance 36 degrees
Fuel 91-octane unleaded
Carb Holley 1000 HP
Jets 84/88 with 6.5 power valve
Other 2-inch Trans-Dapt open spacer
Max Torque @ rpm 620 @ 4,200
Max Power @ rpm 659 @ 6200
Avg Torque 566
Avg Power 383
SOURCE
Carrillo Rods COMP Cams
GM Performance Parts
www.gmperformanceparts.com
Milodon
2250 Agate Ct.
Simi Valley
CA  93065
805-577-5950
www.milodon.net
Brodix
301 Maple P.O. Box 1347
Mena
AR  71953
Manley Performance Products
Lakewood
NJ
732-905-3366
www.manleyperformance.com
Mahle Clevite
Ann Arbor
MI
8-00/-338-8786
Engineparts.Com
Trans-Dapt
Federal Mogul (Fed-Pro gaskets) JE Pistons
Speed-O-Motive
131 W. Lang Ave.
West Covina
CA  91790
6-26/-869-0270
speedomotive.com
Holley
ARP
531 Spectrum Circle
Oxnard
CA  93030
805-278-7223
MSD Ignition
El Paso
TX
9-15/-857-5200
msdignition.com
Professional Products
Hawthorne
CA
3-23/-779-2020
professional-products.com
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