How to Build a 385 Small-Block Engine

Stock-Block Brawler - The Bottom Half of a 385 Stroker

Jake Amatisto Oct 14, 2013 0 Comment(s)
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The following pages cover the component details used to build the 385ci short-block that we’ll be dropping into our ’63 Nova. With LS engines getting loads of coverage in magazines these days, we thought we’d give a conventional recipe a shot by using a combination of today’s off-the-shelf high-performance parts. Over the last several years we have been impressed with what kind of horsepower you can achieve from a small-block with readily available and relatively inexpensive components. It’s a little cliché to use the terms budget and off-the-shelf parts in 2013, especially when you are building an engine that could launch a 3,000-pound car into the single-digit range. We’re not pretending this is an engine everyone can afford, but we want this build to inspire others to be more active in researching what can be built with a phone call, a little hard-earned cash, and a bit of time.

Our two main allies in this build were L&R Engines in Santa Fe Springs, California, and Rapp Racing in Huntington Beach, California. L&R prepped our 350 block, honing, boring, and decking it before applying a coat of black paint. Meanwhile, we ordered the remainder of the components from Summit, ARP, Mahle, Scat, COMP Cams, Moroso, RHS, and TCI Automotive. We also enlisted the help and expertise of Rapp Racing before putting everything together with owner Mark Rapp. This guy not only builds trick engines, but he also races one wicked 9-second, all-motor, leaf-spring Nova, so we knew we were in good hands.

As far as power, we would be ecstatic if the engine makes over 500 hp on pump fuel, but the real goal with this engine is to make enough ponies to run low 10-second times in the quarter-mile and still be able to drive it anywhere. Whether that’s 450 or 500 on 91-octane, the dose of liquid horsepower from an NOS nitrous plate system will be our ticket to propelling our Chevy II to our ideal e.t. at the dragstrip.

Block

The engine block we’re using is a late-model 350 from Summit Racing (PN SUM-150100) that we previously used for a very mild 355. This four-bolt remanufactured block can be had from Summit, fully machined with 0.030 overbore, for around $700. In this build, we increase the cubic inches with a larger bore and longer stroke. A late-model block means it has a one-piece rear main seal, and comes with lifter valley provisions for dog bone retainers. The camshaft and cam retainer area for a late-model block is also different than early blocks, so we kept that in mind when ordering the valvetrain.

Summit 350 Engine 2/21

We contacted L&R Engines out of Santa Fe Springs, California, to freshen up and increase the bore size of our block to 0.040. Other machine work done to the block included decking the head surface and line-honing the main journals to make sure everything was square before assembly.

L&R opened up the bore on the block to 0.040 over (it comes 0.030 over from Summit), making our build a 385ci small-block. Using a torque plate mimics the pressures the cylinder head applies to the block and ensures the bores are square with the heads once it’s fully torqued down.

Line boring the main journals makes each of the four as straight and round as possible; it’s also necessary when going with an ARP main stud kit (PN 234-5608), since they are torqued differently than the stock main bolts the block came with. If you used studs without line boring the block, it could put unequal pressures on the bearing, which could lead to unwanted failure.

Crank & rods

For this build, we’re using a forged crankshaft from Scat Crankshafts in Redondo Beach, California. We ordered a standard weight, chrome-moly piece with a 3.75-inch stroke (PN 4-350-2305700), and a one-piece main seal to match our late-model block.

Scat 6/21

The connecting rods are Scat’s 6-inch forged H-beams (PN 2-350-6000-2100). These will easily handle the horsepower (and nitrous) it takes to make our Nova run bottom 10s. There are actually two versions of the stroker available in the aftermarket, one with 5.70-inch rods and the 6-inch version; we opted for the longer rod for reduced side loading on the engine block.

The rod journals of the crank feature wide journal fillets that required an HX bearing from Clevite in order for the crankshaft to spin smoothly. The H bearing means it’s narrower than standard bearings and the X is for extra bearing-to-journal clearance. If we used stock type bearings, the bearings would bite too hard into the journal and wear out indefinitely.

The main and rod bearing clearance Rapp uses in engines like this is 0.003 inch. Some would consider this slightly on the loose side, but because of the horsepower and rpm this engine will see, it’s necessary. It’s better to be on the loose side and run thicker oil than to have it too tight and spin a bearing during an rpm blast. This cushion of clearance between the main and rod journals also determines the weight and type of oil to use. In our case we’ll run COMP Cam’s Break-In Oil initially, then some 10W-30 once it’s in regular operation.

Pistons

We contacted Mahle for their 4.040-inch flat-top pistons. The skirts are coated with a coating called Grafal that basically provides a small scuff cushion for the piston. The pistons are Mahle’s off-the-shelf flat-tops with a -5cc dish (PN SCB125040F05), which are designed to work with our rod and stroke combination.

Mahle Flat Top 10/21

To mate the pistons to the rods, this handy tool was used and made attaching them a breeze. It basically works by forcing the round-wire lock into place with a twisting motion.

To figure out the top ring gap, we multiplied the bore size (4.040 inches) by 0.0050, and 0.0055 to figure the second ring gap. Taking nitrous into consideration, we gapped the top ring to 0.020 inch and the second ring to 0.022 inch.

With the bottom end assembled, we were in the neighborhood of our desired compression. However, after doing the math, taking the larger bore into account, we decided we’d need a head gasket thicker than the typical 0.039 inch if we planned to run 91-octane without fear of detonation. With the thinner gaskets, we would have been over 11:1 compression, so Trey McFarland at Mahle determined we’d need 0.065 thick gasket in order to get to 10.5:1 with this particular combination.

Oiling System

Moroso Performance handled the oiling system for this build, including the early Nova–specific oil pan (PN 20210), a high-volume oil pump and pickup (PN 22101 and PN 24100), and even the oil filter (PN 22460).

Nova Oil Pan 14/21

We used ARP’s oil pump stud (PN 230-7003) to attach the high-volume pump to the block, and we also put a tack weld on the pump pickup to make sure it doesn’t go rogue during operation.

Moroso’s oil pan baffle (PN 23000) and windage tray (PN 23020) were used in the crankcase of this build; the windage tray is a must for high-performance engines as it keeps the oil in the crankcase in control, increasing power through reduced windage.

Cam & Lifters

The cam we’re running in this combo is a fairly mild, Xtreme Energy hydraulic roller from COMP Cams with 0.510/0.520 lift and a duration at 0.050 of 230 on the intake and 236 on the exhaust side. We actually ordered COMP’s complete cam, lifter and spring kit (PN K08-432-8) for this build. This cam profile we’ll have no problem driving every day. We are however enhancing the specs by running higher ratio rocker arms, but we’ll cover that in the following article.

Xtreme Energy Hydraulic 17/21

The COMP Cams kit came with a double roller timing chain that Rapp installed, making sure to degree the camshaft before cinching it down.

Double Roller Timing 18/21

Other Items

Installing the lifters requires the use of a steel “dog bone” retainer system. The dog bones ensure the lifters don’t rotate in the bores while they are in motion. Mechanical roller lifters have a bar that ties two rollers together so they can’t rotate.

We opted for COMP’s powdercoated timing cover for our 385 small-block (PN 38219), which fit our all-black theme we plan on going with on this engine.

Finishing off the bottom end of this piece was a Rattler harmonic balancer from TCI Automotive (PN 870001). In the next article we’ll cover the top end components and show off the completed engine.

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