Small-Block Chevy Pump Up! Taking a Street/Strip Engine to the Next Level
When Ryan Saiki picked up his street/strip ’70 Chevy Nova, it was already packing a healthy small-block combination. The engine was none too exotic, based upon a factory production GM No. 511 casting 400 block, featuring a 0.040-inch overbore and a Scat crank delivering the stock 3.75-inch stroke. This was enough for 408 cubes. The dished pistons inside produced a compression ratio of 10.5:1 with a set of mildly reworked Canfield small-chamber aluminum cylinder heads. So far, that might sound like your basic mild street combo, but the engine was loaded with a burly 262/270-degree solid roller cam and topped with a big Edelbrock Super Victor single-plane intake fed by a large 4150 carb. As dyno tested, the engine dished out a respectable 532 hp at the crank, and was good enough to push the Nova into the bottom 11s at the strip.
While that kind of performance might be enough for most guys, Ryan Saiki grew up around drag racing, where faster is always the goal. His father, Mike, has been in the game long enough to have built up a small stash of parts, among them a 20-year-old set of AFR 227 heads from one of his old race engines. It didn’t take long for a plan to gel with the idea of wringing a little more power out of Ryan’s small-block Chevy combo.
Powering Up the Small-Block Chevy
Initially, the plan was to upgrade the top end, replacing the rather limited Canfields with the ancient AFRs that were just collecting dust. Though these were older castings, the potential was there for more power. The heads were brought over to Mike’s good friend Bryce Mulvey of Dr J’s Performance, and the transformation began.
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The AFR heads were already fitted with a Jesel shaft mount rocker system from their previous life, in the same 1.6:1 ratio as the stud-mounted rockers on the engine’s original Canfields. The plan was for a full build on the heads, with Manley 2.125/1.60-inch valves, new Manley springs and hardware, and most important, full custom porting by Dr J’s. The treatment definitely breathed new life into the old heads, with the flow bench showing 332 cfm peak flow on the intake side and 228 through the exhaust.
With the heads completed, the engine was pulled for the rest of the transformation. The Chevy gave up its as-cast Super Victor intake manifold for full porting to match the work done on the cylinder heads and get the most of the airflow combination. The existing short-block looked relatively fresh, with negligible bore wear, but it was fully torn down for a rework and freshening. The Scat 3.75-inch crank and Scat 6.00-inch rods were good to go with just a new set of Clevite H and HN series bearings, however the dished pistons were another matter. The old slugs were anything but state of the art, and the dish configuration that produced 10.5:1 compression with the small chamber heads was not going to cut it with the 70cc chamber of the AFRs.
The solution for the piston quandary was a new set of CP Bullet series flat tops along with CP’s 1.5-1.5-3mm ring package. Bryce Mulvey of Dr J’s tells us these high-tech pistons are worth power even against higher-end rivals. Compared with the 1⁄16-1⁄16-3⁄16-inch ring jobber-grade pistons coming out of the engine, a significant power improvement was expected. The change in the piston/head combination raised the compression ratio to 11:1, about a half point better than the old arrangement, but still well within the realm of pump gas use. The block was simply hand deglazed with a three-legged hone and bolted back together with the new pistons and the recycled internals.
Among the parts to be reused, the Comp stick had plenty of lift and duration to get the job done, but the lobe-separation angle at 112 degrees was considerably wider than what the Dr J’s considered optimal. Nonetheless, it was hooked to the crank with a Cloyes roller timing set, dialed to 108 degrees installed centerline, and called good enough. The Jesel rockers were lined to the cam with a set of Isky Red Zone EZ roll solid roller lifters and a team of Manley pushrods. The prepped heads met the decks with a Cometic gasket providing 0.040-inch clearance to the pistons and topped with the freshly ported Super Victor intake and an 850-cfm Quick Fuel carb.
In summary, what we were dealing with here was the old 532hp combo upgraded with the new CP pistons, a half point bump in compression, and the custom top-end work from Dr J’s. The question, of course, was what it would be worth in power output. With a Superflow Powermark DTS dyno at the ready, we were about to find out. The engine was bolted to the dyno and finished with a complete MSD ignition system and a set of 1-7⁄8- to 2-inch dyno headers.
It didn’t take long to quantify the change as the 408 belted out a jaw-dropping 666 hp at a lofty 7,200 rpm. The small-block worked like a buzz saw in the upper-rpm range, tenaciously hanging on to power as the revs climbed the scale. The 532 lb-ft of torque coming in at 5,800 rpm left little doubt that the Chevy was feasting on airflow. While the wide lobe-separation angle was undoubtedly flattening the torque curves in regard to peak torque, the numbers showed more than 1.3 lb-ft per cube. That is healthy territory for any pump gas engine. With a solid 134hp gain coming with the limited changes made, this experienced crew of engine guys made all the right moves.
408 Small-Block Chevy Build Details
As with the rods, the engine’s crank remained the same unit that came out of it, a forged 3.75-inch stroke piece from Scat. Notice the heavy metal inserts in the counterweights used for balance.
In the assembled short-block the deck height of the pistons measured 0.003 inch out of the hole at top dead center. A good active squish/quench is an important factor in producing torque and aids in detonation tolerance.
The bottom end was fitted with a louvered Moroso windage tray and a Melling M55HV oil pump, with the pickup welded to the pump. A Moroso pan buttons it closed.
Although the cam may not have been optimal, the same solid roller that came out of the engine went back in. The Comp stick delivers 262/270 degrees duration at 0.050 inch, is cut on a 112 separation, and was installed at 108 with a Cloyes timing set.
Isky Red Zone EZ Roll lifters are as bulletproof as a solid roller lifter gets. The bushed axle eliminates the danger of needle bearing failure and the catastrophic damage that can result.
Starting with a set of AFR 227 heads from the early ’90s, Dr J’s cut new seats and installed fresh Manley 2.125/1.600-inch valves. These heads received the full porting treatment including the chamber work visible here.
The ports were fully reworked with custom porting, resulting in intake flow exceeding 330 cfm. Note the generous port cross section—just the thing to feed 408 hungry cubic inches
To control the big roller cam, fresh Manley springs provide 260/695 pounds of spring load. The springs were installed with Manley 10-degree locks and titanium retainers
A Cometic MLS head gasket seals the decks and provides a piston to head clearance of 0.040 inch.
The Jesel shaft-mounted rockers are the same 1.6:1 ratio as were the stud-mounted units on the original set of heads. They deliver 0.710/0.680-inch lift from the Comp cam.
The engine came with an Edelbrock Super Victor intake manifold, but it was in as-cast form. For the new combination, the intake was given full competition porting from Dr J’s.
Peeking inside the intake manifold, the extensive modification to the plenum is clearly visible. The work extends the full length of the runners.
Mixing the air and fuel is an 850-cfm Quick Fuel carburetor. This feisty Chevy can take advantage of all the flow it can get.
Vital Specs: 408 Small-Block Chevy
Chevrolet 408 Small-Block DTS Engine Dyno Tested At Dr J’s
This story was originally published in the Spring 2013 issue of Engine Masters.
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