Tech / Tech Projects

Project LS Next (Part 1): The Short Block for our 665-Horse 440 LS Build

 

Editor’s Note: Mike Mavrigian of Birchwood Automotive is back with another cool engine build. This one is a 440 cubic inch LS engine based on Dart’s LS Next iron block. The 10.54:1 compression engine made 665 horsepower and 627 lbs.-ft. of torque on the dyno running high test pump gas. That will get you down the road in a hurry.

In Part One, we’ll go over the block prep, the rotating assembly, and camshaft installation.

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INTRO02

Available in cast iron or aluminum, Dart’s LS Next block combines the best features of the factory LS design with a bottom end based on the tried and true small block Chevy race block design. Other upgrades include thicker decks, priority main oiling, and improved water capacity and flow, especially at #1 cylinder bore. Both standard and raised cam designs are available.

The LS Next does away with the OEM deep-skirt Y-block design for improved crankcase breathing and windage reduction. The Dart block has billet steel 4-bolt main caps, eliminating the need for main cap side “pinch” bolts. Metric threads are retained to accommodate standard LS components, but the main cap bolt holes and primary head bolt holes have been converted to 7/16-14 thread. All head bolt holes are blind, with no entry to water.

Since the lower rails are shortened, there’s no provision for an OEM oil filter and an external/remote filter is required. AN threaded ports are featured on the left side of the block. The oil-out port is shown here. The oil-in port is located towards the rear of the block’s left side. A 1/8-inch NPT port located above the oil-in port accommodates an oil pressure sender.

The block is drilled to accommodate 23-bolt LS cylinder heads. Four extra stud bosses are featured on each bank. These accept short studs that thread into the cylinder head’s deck and are secured with special shouldered washers and nuts that install under the bosses. ARP offers a head stud kit just for the LS Next block.

The lifter boss areas feature offset threaded holes to accommodate either GM LXS race lifters or Jesel’s tie-bar lifters. You can use other tie-bar-style lifters too. If you use 23-bolt cylinder heads, the lifters must have a V-bend tie bar to clear the head stud that passes through the 13/32-inch hole located between the lifter bores. The block design will not accommodate the OEM plastic lifter buckets due to the offset threaded holes between the lifter bores.

The lifter valley has windows for lifter access plus ¼-inch and 1/8-inch NPT ports for oil restrictors. Since we’re using hydraulic lifters, we plugged all four ports.

Our block was finish-machined at Gressman Powersports in Fremont, Ohio. Once the block was registered on the CNC machine, a digital probe located and created data for deck height, cylinder bore centers, and cylinder bore diameters. Each cylinder was first bored to 4.155-inch, then to 4.180-inch.

The block was decked to the top of each bore to square the block and to equalize the distance from the decks to the crank centerline. Finished deck height was 9.2370-inch.

The decks are indexed off the crank centerline for parallelism and the bore centerlines are verified. Using a CNC machine saves a substantial amount of time compared to using block indexing fixtures on older machining equipment.

Once the decks were cut, the top edge of each cylinder bore was CNC chamfered to ease piston ring entry during assembly.

Piston skirt diameter must be measured to determine oil clearances in the cylinder bores. JE specifies that piston skirt diameter be measured at 0.275-inch above the skirt bottoms.

With the block pre-stressed with torque plates, the cylinder bores were finish honed to 4.185-inch.

Scat’s 4340 forged steel stroker crank features a 4.000” stroke and 2.100” rod pins; lightening holes on all rod journals; large fillet radius on all journals; gun-drilled main line; profiled and pendulum-cut counterweights, and straight-shot and chamfered oil holes.

LS crankshaft reluctor wheels are available in either 24 or 58-tooth designs. Our crank is fitted with a 58-tooth wheel. A 58-tooth design provides superior ignition timing accuracy as compared to the early generation 24-tooth version.

Any crankshaft must be balanced to accommodate the specific weight of the rods, pistons, rod bearings, pins, and rings used in the rotating assembly. Our Scat crank had 18.125 grams of material removed from the counterweight edges to get it within 0.04 grams of perfect balance. Considering the weight of oil that will cling and release during engine operation, trying to obtain a zero balance is unrealistic.

JE’s forged pistons have an asymmetric design with a wider skirt on the thrust side and a narrower skirt on the other side. Our pistons feature 0.927-inch free-floating pins, 12-degree valve relief pockets, and an inverted dome for a net piston volume of -14.6cc. No corrections were required during balancing as all eight slugs come weight-matched.

The JE pistons are factory-weight relieved to reduce reciprocating mass.

Our piston compression distance (center of pin bore to deck) is 1.115-inch. Coupled with our 4.000-inch stroke crank and 6.125-inch rods, this provides a theoretical zero deck.

Due to the relatively short 1.115-inch compression height, the wrist pin bore intersects the lower oil ring land. A support rail is installed under the oil ring package to compensate for the void at the pin bore area.

The Scat forged H-beam rods were impressively weight-matched out of the box. The slim profile of the big ends provides added clearance for stroker combinations and large base circle cams.

Each rod is laser etched with a unique number. As long as you pay attention, there’s no chance of mixing up the caps.

The ARP 8740 12-point rod bolts provide increased surface area for positive wrench engagement. Both the bolt head and shank tip feature a dimple to accommodate a rod bolt stretch gauge.

After installing our Mahle Clevite cam bearings, our COMP Cams hydraulic roller cam was lubed with Royal Purple Max-Tuff assembly lube and carefully slid into the block. Valve lift with 1.72:1 rockers is .624-inch. Duration @ 0.050 is 243-degree intake/251-degree exhaust. LSA is 114 degrees.

Main bearing oil clearance was checked by mic-measuring the main journals and bore-gauging assembled main bearing diameters. We had 0.00188-0.00190-inch oil clearance on all journals.

We checked crank counterweight and rod big end clearances to the block. No corrections were needed. Dart does a spectacular job at anticipating stroke clearances, but you should still test fit everything when doing a stroker build.

With the main bearings, crankshaft and main caps installed, crank endplay was measured at 0.0075-inch using a dial indicator.

Our Cloyes timing set has a multi-keyed crank gear that allows maximum advance/retard of 2.5 degrees. The cam gear’s eccentric adjuster button provides maximum advance/retard of 6 degrees.

With the three cam bolts loosened, the eccentric hex-adjust button can be rotated using a hex bit. Cam timing index marks are provided. The cam bolts were treated with Loctite thread locking compound and tightened to 25 ft.-lbs.

When installing the Cloyes thrust bearing to the rear of the cam gear, the black side of the bearing must face the block.

Not all OEM blocks are drilled and tapped to accept a timing chain damper, but Dart thoughtfully provided holes to accept a factory damper.

Pistons and rods organized and ready for final assembly.

With the cylinder walls clean and oiled, an adjustable ring compressor is fitted over a piston and ring assembly. Each piston slid easily into its respective bore with just simple hand pressure.

Each rod bolt (treated with ARP moly) was torqued to spec in several steps, alternating bolts on each side of the rod.

Each rod bolt was checked with a stretch gauge. The gauge is indexed onto the bolt prior to installation and zeroed at its free length. Once the bolt is torqued, the same gauge is then used to measure how much the bolt has stretched. All of our rod bolts were tightened to achieve 0.0045 to 0.0046-inch stretch. Scat specifies a max of 0.0046-inch

Although rod big end side clearance was checked during test fitting, this was verified at 0.014-inch again during final assembly.

The cam was checked with a degree wheel. The timing and lobe specs were dead-on.

The finished short block awaiting the oiling system, cylinder heads, and intake.

The LS Next Block

Dart’s LS Next block has numerous improvements that eliminate some of the weaknesses and compromises of factory LS blocks. The biggest change is the elimination of the factory Y-block design with the extended oil pan rails and separate crankcase bays. The crankcase is more like a traditional small block Chevy, so the block is stronger and windage is reduced. The block requires a special oil pan; Stef’s, Canton Racing Products, and Moroso make them.

  • Other LS Next features include:
  • Priority main oiling system (main bearings get oil first, then cam bearings)
  • Deck height is 0.002-0.005 inch taller to accommodate additional machining
  • 1.5 inch press-in freeze plugs instead of OEM threaded plugs
  • Accommodations for 23-bolt type cylinder heads
  • Accepts a stock style oil pump or external pump

The shorter oil pan rails require the use of a remote oil filter and a factory style Cloyes timing gear. Double row timing chains require block clearancing. The camshaft retaining plate and bolts are unique and supplied with the block.

A Dart block completion kit is a good investment. It includes six 1.5-inch freeze plugs; two bellhousing dowels; four head deck dowel sleeves; two 1/4 inch NPT male hex head plugs for water drains; seven 1/4-inch NPT female hex plugs; and three 1/8-inch NPT female hex plugs.

Block Machining

Our block was finish-machined at Gressman Powersports in Fremont, OH. The block was bored, decked, and squared on a CNC block machining center. Cylinders were bored from 4.125 to 4.180 inches in two steps, leaving 0.005-inch for final honing. Deck height came in at 9.2370 inches.

The block was final-honed using torque plates and the ARP head studs that will be used during final assembly. The finished 4.185-inch bore diameter accommodated the required 0.0055-inch piston-to-wall clearance for our JE pistons. The main bearing bores were checked for size and alignment, but Dart did such a nice job that no additional honing was necessary.

Threaded holes should be checked on any new block. It’s common for threaded holes to have the threads cut too short. During pre-fitting of various components, we tapped the 8mm x 1.25 holes for the oil pump and front cover fasteners about 5mm deeper. All NPT holes (especially at the rear of the block) were tapped a bit deeper as well in order to prevent the plugs from interfering with the rear engine cover.

We completely deburred the block and sprayed it with heavy-build urethane primer. The primer was sanded smooth before spraying the block Valspar Silver Sunshades, an aluminum/silver color. Once the basecoat dried, two coats of urethane clearcoat were applied.

Crankshaft Balancing

The Scat forged crankshaft was precision balanced at Medina Mountain Motors in Creston, OH. Bobweights were assembled once pistons, connecting rod big and small ends, rod bearings, rings, wrist pins, and pin locks were weighed. The crank was internally balanced to within 0.2 grams. Balancing was achieved by removing a total of 18.125 grams from the front and rear counterweights—no heavy metal was needed.

Camshaft

We chose a COMP Cams hydraulic roller camshaft for this engine. Specifications are:

  • Gross valve lift: 0.624-inch with 1.7:1 ratio rockers
  • Advertised Duration: 292-degree intake/300-degree exhaust
  • Duration @ 0.050-inch: 243-degree intake/ 251-degree exhaust
  • Lobe separation: 114 degrees
  • Intake valve timing @ 0.006-inch: 34-degree open BTDC/78-degree closed ABDC
  • Exhaust valve timing @ 0.006-inch: 86-degree open BBDC/ 34-degree closed ATDC

Recommended endplay is 0.005-0.010-inch; ours measured 0.006-inch.

Crankshaft Installation

Dart obviously had stroker cranks in mind when they designed the block—there were no clearance issues whatsoever when we checked counterweight to block clearance. Main bearing clearance measured 0.00188-0.00190-inch. Crank endplay was 0.0075-inch.

During final installation, the 7/16-inch main cap bolts were snugged to 65 ft.-lbs in three stages: 30 ft.-lbs, 45 ft.-lbs, and 65 ft.-lbs. Crank rotation was checked after each stage—we could rotate the crank with two fingers on the snout. The Mahle/Clevite main bearings were coated with Royal Purple Max-Tuff assembly lube.

Timing Set

After installing a key in the crank snout’s rear (long) keyway, the Cloyes crank gear was tapped into place. The “standard” timing slot was engaged to the key (the rounded slot). This places the zero timing mark counterclockwise relative to the key. The oil pump drive gear was installed on the same key.

The cam gear features a Torrington bearing that installs at the rear of the gear. The black side of the bearing must face the engine block. The eccentric cam timing button fits in the cam gear’s drive pin hole. The rear of the button engages the camshaft’s dowel pin. The eccentric button is adjustable so you can fine-tune cam timing during cam degreeing.

After soaking the timing chain in 30W engine oil overnight, we installed the cam gear and chain and tightened the ARP cam gear bolts to 25 ft.-lbs. A dab of Loctite 242 helps secure the bolts.

Pistons

Our JE pistons feature an asymmetric design. The thrust side has a conventional-width skirt, while the unloaded side skirt is narrower. This saves weight while adequately supporting the thrust side of the piston. To give you an idea of the difference in skirt width, our piston skirts are approximately 2.030 inches wide on the thrust side and approximately 1.460 inches on the non-thrust side, as measured from the bottom of the skirts. The thrust sides face the outboard side of the right bank cylinders and the inboard side of the left bank cylinders.

Since the on-center balance weight of the piston (relative to the wrist pin bore centerline) is altered, the pin bore centerline was moved about 0.020-inch toward the piston’s thrust side to compensate.

Piston/Rod Assembly

Our Scat forged 4340 steel rods are an H-beam design with doweled caps, and are profile clearanced for stroker applications. The rods feature a center-to-center length of 6.125-inch and are fitted with ARP 8740 12-point bolts.

Since the pistons are asymmetrical and are cylinder bank-specific, each piston dome is lightly stamped by JE with a “FRONT” designation and an arrow symbol. When installing pistons on the connecting rods, the larger chamfer on one side of the rod big ends must face forward on the left cylinder bank and rearward on the right bank.

Piston Rings

The pistons came with a ring set and support rails that install on the bottom of the oil ring land. The pistons’ short compression height means the wrist pin bore slightly intersects the oil ring groove. The rails are needed to provide oil ring support at the outside of each pin bore end. Install each support rail so that the small male dimple aligns at the center of the pin bore area and faces downward. This dimple serves as a stopper to prevent the rail from walking and keeps the rail’s gap well away from the open pin bore cutouts.

The top and secondary rings required file fitting. JE recommends ring end gaps of bore size x 0.0045-inch for top rings and bore size x 0.0050 inch for the secondary rings. We used a Summit Racing bench-mounted ring filer to create a 0.019-inch gap for the top rings and a 0.021 inch gap for the secondary rings.

Even though the cylinders were CNC machined and accurately honed to size, we file fit each top and second ring on a per-cylinder basis, keeping them organized for each individual cylinder. This probably isn’t necessary, but it allows you to verify proper ring gap for each cylinder.

Piston/Rod Assembly Installation

We installed the rods and pistons using an adjustable Summit Racing piston ring compressor. It features a split design so the tool can be adjusted for bore diameters from 4.120 to 4.220-inch. A tapered inner wall smoothly compresses the ring package as the piston slides into the cylinder bore. We used a plastic piston hammer with an extended snout to gently tap each piston down while aligning the rod’s big end onto the crank journal.

The Dart LS Next block has notches at the bottom of the bores for rod bolt clearance. Our closest rod bolt head to block clearance was approximately 0.300-inch, so no additional block notching was required.

Scat recommends the rod bolts be torqued to 64 ft.-lbs using ARP moly lube. Bolt stretch is not to exceed 0.0046-inch. We used a rod bolt stretch gauge to check this. With each bolt torqued to spec, rod bolt stretch measured between 0.0035 and 0.004-inch.

We achieved the desired 0.002-inch rod bearing oil clearance by using Clevite HNK upper bearings and Clevite HXNK lower bearings. Rod sideplay measured 0.0018 to 0.0019-inch at all big end locations.

In Part Two of the LS Next 440 build, we’ll dive into the oiling system, cylinder heads, and valvetrain.

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5 Comments

  1. Why are the bearing clearances so tight? Under 002 on the mains and just 002 on the rods? way to tight for a engine like this. And rod side clearance under 002?? are these misprints?

  2. OnAllCylinders says:

    According to the builder, bearing clearances were set for use with 0W-40 or 5W40 oil. Rod side clearance is 0.018-0.019”

  3. Pingback: Project LS Next (Part 2): Installing the Oil System and Valvetrain on Our 665-Horse LS Build - OnAllCylinders

  4. Wondered what ever happened to you after the race Retread Challenge I was on your pit crew as the jack man What ever happened to Steve Walker

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