The heads received a number...
The heads received a number of valvetrain components from Comp, including factory long-slot rockers, guide plates, and rocker studs.
To save time and money, we decided to build an engine that duplicated the power potential of the original 327s without being an exact replica. For example, while the early 327s were equipped with two-bolt blocks, we sourced a four-bolt block from L&R machine. And while the original engines came with small-journal steel cranks, we outfitted our late-model block with a large-journal cast piece. Fortunately, none of these changes would have any impact on output.
There was one area, however, in which we were forced to deviate in a way that might stir controversy. Since the 327s came equipped with 11.0:1 compression, we needed to duplicate this reading on our test motor. The number was arrived at using the 64cc combustion chambers on the fuelie heads (more on these later) and a set of forged aluminum pistons from Probe Racing. Rather than going with a set of reproduction TRW forgings, we opted to have Probe duplicate the (roughly 7.5cc) domes using one of its own forgings. The only downside to this route was that the compression height differed from stock and therefore required the use of a 6.0-inch connecting rod. Like the cast crank, this minor discrepancy shouldn't affect the outcome of our back-to-back tests. Whether we'll be chastised on the Internet for running a long rod in the legendary small-block remains to be seen.
L&R freshened up the stock...
L&R freshened up the stock heads with a light surface and a factory-style valve job. The reconditioned heads flowed 205 cfm on the intake and 140 cfm on the exhaust.
With our short-block taken care of, we moved on to the heads, cam, and induction. For the cam, we used an Elgin Industries reproduction of the solid-lifter "Duntov 30-30" grind (0.484-inch lift, 254-degree duration, 114-degree lobe separation) that came in both the L76 and the L84. Looking at the specs, this would seem to be a pretty aggressive cam, but the combination of relatively short lift and long duration produced a mild ramp rate that was actually easy on parts.
When it came to the heads, we were able to obtain a suitable set of 461 castings from Rick Stoner at Westech Performance. All we did was install a new set of Pro Comp valves, perform the requisite valve job, and add a set of heavy-duty valvesprings (130 pounds of seat pressure and around 325 pounds open) suitable for our flat-tappet cam.
We also took the liberty of flowing the heads before installation. The 160cc intake ports flowed 205 cfm at 0.600 lift, while the exhaust ports flowed 141 cfm at the same lift. More important for our needs was the flow at 0.500 lift-just over the 0.484 offered by the factory cam. There, the intake checked in at 206 cfm, while the exhaust flowed 140 cfm. While these numbers aren't anything special by today's standards, they set the standard for small-block performance in their time.
Topping off the fuelie heads...
Topping off the fuelie heads was an original high-rise intake wearing a 461 casting number. This dual-plane unit came courtesy of Rick Stoner from Westech.
Before getting to the induction systems, we should mention that our test motor required a number of other smaller components in order to be completed. In addition to supplying the 6.0-inch connecting rods for the build up, Pro Comp came through with things like a high-volume oil pump and pick up, a neutral-balance damper, and stainless steel intake and exhaust valves.
In terms of ignition, the early 327s were offered with transistorized systems. Rather than attempting to go the numbers-matching route, we once again opted for something a little more modern, this time to eliminate any chance of misfires during testing. The Rochester-injected setup was run with the specific distributor it required, but the carbureted motor was equipped with a modern MSD electronic unit. Basically, we wanted to run both combinations in a state of optimized tune in order to see what each of the induction systems had to offer.
Unfortunately, the original...
Unfortunately, the original intake had previously been modified to eliminate its center divider. We cured this problem by fabricating a replacement divider out of sheet aluminum. Back-to-back tests on both configurations found a significant torque loss (7-8 lb-ft) without the divider, along with a minor power gain (2-3 hp) at the top of the rev range.
Rather than run a factory...
Rather than run a factory Holley 3310, we opted for a modern version in the form of a 750 Street HP. With the proper jetting, the two carbs would perform equally well on our 327.
If you must have a numbers-matching...
If you must have a numbers-matching carburetor on your L76, check with the guys at Pony Carburetors. They have a wide variety of original, restored carbs for muscle-car and Corvette applications.
Rather than run the engines...
Rather than run the engines with the factory cast-iron exhaust manifolds, we chose a set of long-tube dyno headers. Note that we also ran them sans accessories with a Meziere electric water pump.
On the dyno, the carbureted...
On the dyno, the carbureted L76 produced peak numbers of 355 hp and 366 lb-ft of torque.
Next up was the factory fuel...
Next up was the factory fuel injection. This system came courtesy of fuelie legend Chuck Smith and retired Delta Airlines captain Mark Detwiler.