The small-block Chevy has enjoyed a long, happy life. Sure, the current LS derivatives are quite far removed from the original, but millions of Gen I Mouse motors continue to provide the motivation to everything from stationary irrigation pumps to 8-second drag cars to LeMans-winning Corvettes. Naturally, this list also includes all manner of boulevard bruisers, street stompers, and resto rockets. Heck, we've even seen little Chevy's under the hood of brand-X machinery. The continued popularity of the small-block is not surprising. Take a look at the combination of power potential and parts availability, then multiply that by the cost quotient, and you have the makings of a real success story. Add in the countless millions of potential project engines just sitting around at junkyards throughout the world, and it is easy to see why enthusiasts continue to embrace it. In today's economy, the traditional SBC just makes great sense.
True enthusiasts, especially those raised on performance during the heyday of the muscle car-era, may look at this story's subhead and immediately think of the 365hp L76 327. An excellent choice of a small-block to be sure. But alas, this is not an article on how to restore your L76. This one's 350-based, and with cast-iron factory heads and a hydraulic cam, might well be a step up in performance thanks to the broader torque curve. Unlike the high-strung performers of yesteryear, the elevated power offered by this mild mannered combination comes with no penalty in idle quality, drivability, or the need to run over to the local speed emporium or track for gallons of expensive race fuel to achieve maximum performance. No, it'll run all day long on regular unleaded.
Like most rebuild stories, our 365hp mill started out life as something much less extraordinary. The 350 was found rusting away in the bowels of a local wrecking yard. The mid '70s 3/4-ton pickup that housed it was well past its prime, but lurking within was a diamond in the rough. Purchased for a mere $90 (wrecking yard special), the complete engine turned out to be the more-desirable four-bolt main block, though a two-bolt block would certainly suffice for this particular build. The high-mileage motor was disassembled, and found to be in quite good shape. Hardly exotic or even desirable by enthusiast standards, the 882 (common SBC smog era castings) heads featured both small valves (1.94/1.50) and large 76cc combustion chambers. The heads showed all the classic signs of high mileage, but we weren't concerned, since the heads would be subjected to a complete rebuild (including larger stainless steel valves, in addition to performance porting). Upon final disassembly, we were pleasantly surprised to see the rod and bearings (and therefore the stock cast crank) in decent shape, and cylinder walls free of major scuffing. Basically, it looked like we had a good rebuild candidate for our 365hp build up.
The first step in the was to build a solid foundation. Our four-bolt 350 was taken to L&R Automotive in Sante Fe Springs, California, for the necessary machine work. The block was bored and honed to accept a set of 0.030-over forged JE replacement pistons. The flat-tops featured valve reliefs to accept cams up to 0.525 lift, more than we planned for this adventure. The piston design worked with our 75cc chamber heads (deck surface milled slightly) to produce an 89-octane friendly static compression ratio of 9.1:1. Note this was a far cry from the 11.0:1-plus compression ratios run on the original 365hp motors. L&R Automotive also took the liberty of hot-tanking the block and installing new cam bearings.
To our surprise, the cast crank was still standard and in excellent shape. We took the liberty of micro polishing the crank just to make ourselves feel better, but it was actually good to go as it came from the wrecking yard. The forged pistons were used in conjunction with a set of used LT-1 pink rods L&R had laying around. Reusing the stock rods can save a few bucks, but we liked having the pink rods for future bench racing sessions. The aftermarket is full of relatively inexpensive forged rods, but our sub-6,000 rpm motor required no such hardware. We did pop for a new harmonic balancer, as the high-mileage unit looked ready to give up the ghost at any moment.
With our short-block assembled, it was time to turn our attention to the power portion of the build up. While a quality short-block is important, the cylinder heads, valvetrain, and induction system are really the determining factors in terms of eventual power output.
First on the list was a suitable camshaft. Since this motor was intended for daily street use, we wanted to avoid any radical cam grinds. Chevy put a ton of duration in its factory performance cams in the '60s, something that inevitably hurt drivability. We erred on the conservative side in terms of cam profile, choosing a mild PowerMax hydraulic flat-tappet piece from Crane Cams. The dual-pattern, emission-legal cam offered a 0.427/0.454 lift split, 204/216-degree duration split (at 0.050), all ground on a 110-degree lobe separation angle. Crane also supplied the necessary hydraulic lifters. Again, note the mild hydraulic cam was a far cry from the solid/mechanical cam run in the original 327. The hydraulic cam made valve adjustment a set-it-and-forget-it proposition.
Next on the to-do list were the cylinder heads. Though a number of great cylinder heads (factory and aftermarket) exist for the small-block, we stuck with the stock castings. Producing 365 hp using a set of aftermarket heads is a walk in the park, but doing so with stock (albeit ported) hardware is much more impressive, not to mention cost effective. L&R Automotive was also responsible for the head work, including porting and installation of the larger 2.02/1.60 stainless steel valves (from S.I.). According to the flow bench, the porting and oversized valves freed up an additional 30-35 cfm per runner. The extra head flow allowed our small-block to take full advantage of the extra lift offered by the Crane cam. Naturally, the 882 heads received a suitable valvespring package to work with the revised cam specs. The stock springs were long since worn out, and inadequate even when new. L&R also set up the heads to accept screw-in rocker studs and guide plates, as factory press-in rocker studs have a tendency to pull out with increased spring pressure. Cost for this would be $725 retail.
The change allowed use of a set of non-self aligning Crane 1.5 ratio roller rockers. It is possible to retain the stock stamped-steel rockers, but given the slightly higher engine speed (over stock) of this new combination, we wanted the extra insurance and valvetrain stability offered by the roller rockers.
With our long-block basically finished, the 350 was missing only the induction, exhaust, and ignition system. When it comes to street motors, forget all about the trick single-plane and tunnel ram intakes. If you want a broad, usable torque curve with plenty of top-end power, stick to a good dual-plane intake. For our 350, we chose an Edelbrock Performer RPM Air-Gap intake. The RPM version offers superior flow compared to a traditional Performer, while the air gap feature theoretically allows for airflow to help cool the individual runners. This cooling feature is even more important once the motor is installed in a vehicle. The RPM intake was topped off with a Demon Fuel Systems 650 Street Demon carburetor. A similar size Holley Street Avenger or even a big Q-jet (or Edelbrock equivalent) would likely work just as well on this combo.
Knowing what goes into a motor must also eventually come out, we equipped the small-block with a set of 1-5/8-inch FlowTech headers. The headers were run into a 2.5-inch dyno exhaust featuring 18-inch collector extensions. Naturally a full-length exhaust system may rob the motor of a few horses, so too will the installation of the accessories and water pump. Our dyno session included a CSI electric pump, no accessories, and the MSD distributor set to provide 35 degrees of total advance. The ported cast iron heads seemed to run best at 35 degrees, something we attribute to the minor combustion chamber polishing performed as part of the porting.
While we were anxious to find out if the combination produced the desired results, we curbed our impatience and allowed the motor a good 40-minute break-in period. After a few short whacks to verify the air/fuel curve, we let the hammer fly and were rewarded with peak readings of 367 hp and a whopping 422 lb-ft of torque. The mild cam timing allowed the motor to produce peak power at just 5,200 rpm, a fact that should help ensure a long life.
The low peak-power rpm also produced an impressive torque curve. Not only did the motor produce 422 lb-ft at 3,900 rpm, but the 0.030-over 350 produced over 400 lb-ft for nearly a 2,000-rpm spread. Even way down at 2,500 rpm, the impressive combination produced nearly 400 lb-ft of torque. It is torque like this that will allow this 365hp version to motor past the high-winding L76 327s of yesteryear. Given the mild cam, ported stock heads, and minimal compression, we were quite pleased with the entire powercurve.
That the motor made peak power at only 5,200 rpm indicates that we had plenty of power potential left, should we elect to run a wilder cam profile or a set of aftermarket cylinder heads. Is the build up of a 365hp small-block that thumps out 422 lb-ft. of torque earth shattering? Probably not. But besting the small-block legends of yesteryear using ported smog heads, a mild cam, and 9.1:1 compression should be considered at the very least, mildly amusing.
Spec Sheet 365-HP 355
- Block: 4-bolt Chevy
- Crank: Cast 3.48-inch Stroke
- Rods: LT-1 Pink 5.7 inches
- Pistons: JE Pistons Flat-Top Replacement Single-Eyebrow (9.1:1)
- Bore Size: 4.030 (0.030 over)
- Compression Ratio: 9.1:1 with 76 cc chamber
- Heads: Chevy Iron 882 casting-Hand Ported by L&R Automotive
- Intake Valve Size: 2.02 (originally 1.94)
- Exhaust Valve Size: 1.60 (originally 1.50)
- Cam: Comp Crane PowerMax
- Lift: 0.427 n, 0.454 ex
- Duration (@ 0.050): 204 in, 216 ex
- Lobe Separation: 110 degrees
- Intake Manifold: Edelbrock Performer RPM Air Gap
- Carburetor: Demon Fuel Systems 650 Street Demon
- Distributor: MSD Billet
- Headers: Flow Tech 1 5/8-inch
- Exhaust: 2.5-inch (Dyno)
- Mufflers: None