Not long ago, in a land infested with high-compression musclecars and four-speed bruisers, the 396ci Chevelle was a respected performance car even when predators like 428SCJ Mustangs and Boss 429s prowled the boulevards looking for prey. The little 396 could hold its ground against the more nimble small-block cars and could certainly beat up on many 383 Mopars and 390 GT Fords. The 396 wasn't a heavyweight like an LS6 454, but it enjoyed a respected performance legacy.
The '66 SS 396 Chevelle was the first full-production-run Chevelle to get the 396. There had been 201 Z-16 Chevelles built in 1965, which became the prototypes for the following year. The '66 396s came in three versions: the Q-jet-topped 325hp version, the 600-cfm Holley-fed 360hp version with oval-port heads and a hydraulic cam, and the more radical 375hp 396 with a mechanical cam and rectangular-port heads.
Back in the day, everybody wanted the 375hp version. When the author bought his '66 Chevelle in 1971, it came with the 360hp version with the "lo-po" oval-port heads. Now fast-forward to rebuild time for this aging musclecar. The engine suffered through an early rebuild and made a disappointing 342 hp on the dyno at 5,000 rpm complete with oversized 17/8-inch headers and a single-plane intake back in the mid-'80s. We decided to freshen it up and rebuild it close to an original 360hp engine with a few refinements.
The steel-crank bottom end was virtually new, using forged pistons, but it had been built in 1980 when the only people using torque plates for honing were Pro Stock racers. We figured we could improve the ring seal with a "round" cylinder wall prep, so we pulled the engine completely apart. This was good because the bearings were less than perfect, although the crank survived unscathed. After taking >> the block to Jim Grubbs Motorsports in Valencia, California, our concerns were justified when owner Jim Grubbs reported significant shadows on the cylinders after the first honing pass with the torque plates installed, which indicated that the bores were anything but round with the heads bolted on. For the freshen-up, we used new Federal-Mogul rings and bearings, but we had to resort to using a second set of +1 performance bearings to mix with the standard rod and main bearings to establish the proper bearing clearances. The original 396 oil pan had seen better days, so we replaced it with a Milodon pan, oil pump, and windage tray to update the lubrication system. Combined with a one-piece oil-pan gasket from Fel-Pro and a Milodon timing chain cover, we had the bottom end dialed in with little difficulty.
Next came time for the cam selection. Since this engine was destined for mostly Saturday-afternoon cruising duties with an occasional blast down the 1,320, we wanted power, but also something similar to the original factory 360hp hydraulic-lifter cam. After a little research we came upon the Crane PowerMax 272 cam, which offered very similar timing numbers at 0.050-inch tappet lift. The Crane was within 2 degrees of the factory cam at 0.050-inch tappet lift on the intake but offers 10 degrees more exhaust duration. That all sounded good, so the Crane got the chance to prove its mettle.
Next on our priority list came the heads. Conventional wisdom has shown us that oval-port heads are the right choice for a 454. If anything, our 260cc oval ports are perhaps a little big for a small 396 Rat, but that's what the factory bolted on, so we intended to make the most of these castings. We employed new stainless steel valves from Federal-Mogul and then hit the area directly underneath the valve seats with a die grinder doing a quick, two-hour pocket-porting job. We removed what was necessary to improve the radius into (or out of) the combustion chamber, but we didn't try to unshroud the valves by moving the chamber walls back. The final modification was to include a set of Viton rubber positive valveguide seals to ensure very little oil would enter the chambers.
Once the long-block was reassembled, we also added a set of Crane hardened pushrods and a set of 1.7 roller rockers because we remembered having to constantly battle rocker-arm problems with the original Rat. Topping off the valvetrain was a slick set of PML cast-aluminum Chevrolet-script valve covers that gave our 30-something Rat a contemporary look with a hint of nostalgia. Since we were looking to maintain the general appearance of our 396, we also decided on an Edelbrock Performer dual-plane rather than a Performer RPM, which is much taller with more power potential. The original 360hp intake was a cast-iron monster that belongs in a museum and not on the car, so we elected to go with the Performer.
We cheated in a way with the dyno test, since we went with an HEI distributor much larger than the original points-type distributor, to which we added a set of universal MSD plug wires. We will probably change this to a Pertronix or other conversion to maintain the original image.
Of course, we couldn't just run cast-iron manifolds on this engine, so it had to have a set of Hedman headers. Combined with a Flowmaster exhaust system complete with the larger Big Block II mufflers, this will make this combination quiet yet powerful.
Since we intended to keep this engine within the confines of its stock mild-hydraulic-cam
The '65 and '66 big-blocks required a grooved rear-cam bearing along with a grooved rear j
This engine had very little time on the forged Federal-Mogul pistons, so we just added new
We measured all the bearing clearances, which required using portions of +1 rod and main-b
We didn't have the right sized tapered-ring compressor, so we had to resort to old-style c
We don't build an engine now unless we can torque the rod bolts using an ARP rod-bolt stre
We somehow managed to align the wrong marks on the timing set, because the circle on the c
We also wanted to tune up the cylinder heads, so we performed a minor porting effort on th
Many engine builders do not recommend lapping valves, but we made the effort to ensure tha
We also took the time to use a height mic to measure and customize each valve's installed
Fel Pro makes an excellent one-piece oil-pan gasket for these Rat motors that is certainly
We buttoned the bottom end together with a Milodon cast-aluminum timing-chain cover, oil p
After the heads were reassembled, we sealed everything up with a pair of Fel-Pro compositi
We purposely installed the valvetrain before installing the intake so that setting the val
It's much easier and less messy to set the valves before you fire the engine. These are Cr
Crane has created a series of blueprint cams that duplicate several popular original factory big- and small-block cam-shafts. These include both hydraulic and mechanical-lifter cams. The following is a list of all the small- and big-block Blueprint cams.
300hp 327 hydraulic
350hp 327 hydraulic
330hp 350 mechanical
290hp 302 mechanical
325hp 396 hydraulic
350hp 396 hydraulic
345hp 396 hydraulic
375hp 396 mechanical
435hp 427 mechanical