Engine Tech: Borowski Builds Mild-mannered 427ci With LS Next Block

LS-based engines have earned notoriety for power and performance while becoming one of the most popular choices for both drag racing and street-engine swaps. They have been strong, reliable engines in most applications, but then racers and engine builders soon began leaning on them with longer strokes, higher rpm demands, stronger boost levels in addition to other traditional paths to power.

Unfortunately, these power quests sometimes revealed problems which ultimately prompted various upgrades and a few elegant solutions from the aftermarket. Such is the case with the Dart LS Next advanced cylinder block, a design refinement targeting some questionable design elements of the factory LS platform. The new block boasts hardcore racing features designed to upgrade oiling and crankcase breathing functions.

In all our power and calibration testing we encountered no oiling or bearing issues. — Dave Livesey, BRE engine builder

Engine builders are certainly selective about the parts dedicated to their signature crate engines; particularly since they serve as mobile billboards for the shop’s engine-building expertise. Borowski Racing Enterprises in Rockdale, Illinois, is no exception. Building on a solid reputation established by founder Ted Borowski, new owner Ken McCaul decided to groom a new line of Chevrolet-based crate engines to serve the company’s expanding customer base. He took a hard look at existing OEM and commercial crate engine packages to identify the most desirable characteristics and components capable of serving a broad range of customer requirements. 

Recognizing the problem

“We didn’t necessarily want to dismiss the known power and cost effectiveness of traditional Chevy small blocks, but couldn’t ignore the tremendous popularity of GM’s LS engines and their growing resume of performance power parts,” says McCaul. “Being primarily a race shop with emphasis on drag racing, circle track and some marine applications; we considered all the important factors with particular emphasis on power potential and good longevity.”

(Left) The unskirted LS Next block adopts the proven Gen 1 small-block Chevy style crankcase configuration, but remains all LS up top. It’s currently available in cast iron and soon in aluminum. (Right) Note main oil gallery plug adjacent to cam tunnel and just below the two lifter galleries. Vertical oiling passage leads to the camshaft journals. Larger angled passage comes from the low volume priority feed main oil gallery ensure priority oil feed to the mains first and the camshaft second.

(Left) The block accepts a standard LS rotating assembly (left). Front and rear billet steel caps utilize four straight bolts. (Center) Note that crank placement is not identical to a small block, but slightly higher in the block to help accommodate correct fitment of LS front cover and oil pan components. Borowski used a Callies Compstar forged crankshaft fully compatible with any LS or LS Next block. (Right) Standard reluctor wheel makes this an easy bolt in and an ATI precision balance keeps things humming smoothly.

“We ultimately chose the LS design to capitalize on its current popularity and compatibility with current muscle cars and electronic fuel injection systems,” McCaul confirms. “But we wanted to take advantage of the new features offered by the LS-Next block from Dart Machinery.” 

LS Next upgrades

Among the desirable attributes it offers are full priority main oiling with a stepped main oil gallery to ensure equal pressure and volume at the front of the block and a lifter gallery crossover passage with restrictor provisions. What makes the LS Next different is its traditional Gen 1 SBC-style lower end, eliminating the LS Y-block configuration and aligning the crank centerline with the oil pan rails. So it’s a hybrid construction. Gen 1 small-block style on the bottom and Gen III/IV LS small-block on the top; eliminating the possible high-rpm power fade and concern of separate main bays in the crankcase in the Y-Block design LS engine. This took more than a little engineering to figure out, but Dart’s Richard Maskin and knowledgeable contributors such as David Reher saw the opportunity.

Off-the-shelf Diamond flat-top pistons with standard valve reliefs were perfect for this application, yielding an 11.4:1 compression ratio with the standard L92 head combustion chambers. They swing on Callies Compstar H-beam rods fitted with ARP-2000 rod bolts.

LS Next Performance Features

  • Proper windage control
  • Siamese cylinder bores
  • Cylinder barrels extended .375-inch for improved piston stability with long strokes
  • 6 head bolts per cylinder
  • Special RMR Iron Alloy
  • 4.000- or 4.125-inch cylinder bore w/ 4.200-inch maximum
  • 4.200-inch x 4.100-inch maximum bore x stroke
  • 454ci maximum
  • Stock LS camshaft position
  • Accepts standard LS camshaft belt drive or chain drive
  • 1.565-inch O.D. camshaft snout
  • .275-inch cylinder wall @ 4.185-inch bore
  • 9.240-inch deck height
  • .625-inch deck
  • 1.500-inch freeze plugs
  • Cam retaining plate
  • Billet Steel 4-bolt splayed main caps w/center thrust
  • .8427-inch to .8437-inch lifter bore
  • Up to .937-inch keyed lifter bore w/ 1.062-inch bushing
  • Melling or stock LS oil pump
  • Requires remote oil filter
  • Special oil pan required: Moroso, Canton and Stef’s
  • Stock LS style rear main seal with factory cover
  • Factory LS starter, driver/passenger mounting
  • Main bolts: inner 7/16-inch x 3.600-inch; outer 7/16-inch x 2.900-inch
  • Studs holes: head 10-bolt pattern with 7/16-inch, 3/8-inch, and 8mm sizes
  • Stud length in Block: 1.000-inch thread depth
  • Factory LS timing cover and front seal
  • Weight: 227 pounds w/main caps

Borowski engine builder Dave Livesey was the point man on this project. On the shop’s  first three LSN blocks, the assignments were a pair of large-displacement, normally aspirated versions and one Whipple supercharged street engine.

The initial test engine shown here was built with block number 009 from the first batch of production units. It’s a 427ci pump-gas, hydraulic roller, EFI street engine delivering 640 smooth horsepower. 

“We used a 4.000-inch Callies Compstar crank and 6.125-inch rods; not the cheapest stuff and not trying to be.” reports Livesey. “The pistons are off-the-shelf Diamond flat tops giving a compression ratio of 11.4:1 with Chevrolet’s CNC ported L92 cylinder heads. We touched up the factory valve job on the cylinder heads with our Newen CNC, and used stock valves and seats, but added PAC 1219x beehive springs.”

The LSN block accepts a stock LS front cover with a Cloyes adjustable timing set underneath and stock gaskets and seals all around. The splayed mains accept a Moroso aluminum pan with a spacer to make up the difference from eliminating the Y-block crankcase, and a Moroso pickup provides the correct sump pickup depth. Initial tests observed 22 psi oil pressure at idle with the stock pump and 40 psi under power. But with a standard volume Melling pump and optimum bearing clearances Borowski observed too much oil pressure. The team substituted a Melling M55 high volume yellow spring which did not provide the improvement they were seeking.  Finally they obtained a more desirable 30 psi at idle and 52 psi at 7,200 rpm with the Melling pink spring. 

“Melling is currently developing a new low volume pump so you won’t bypass so much oil,” Livesey adds.

The front end is finished off with an ATI damper and a billet serpentine belt accessory drive kit. Up top the heads are mated with an Edelbrock L92 style intake manifold with a 4150 style carb flange since there are no Dominator flanged manifolds for the L92 heads. 

“We chose a FAST 1,375 cfm single-port throttle body and later a 4-barrel Holley throttle-body to match the Holley HP EFI system. Both made identical power and we were very impressed with the ease of tuning and rapid configuration of the Holley EFI system,” says Livesey.

Testing camshafts

Borowski tested two different hydraulic roller cams with more duration on the exhaust; starting with 239/255 degrees duration at .050-inch, .624 lift on the valves with 114 degrees lobe separation installed at 112 degrees. That setup made 633 horsepower at 6,700-6,800 rpm with 556 lb-ft torque at 5,200 rpm on 92 pump gas with the air fuel ratio at 13.0 to 13.1. The second cam stepped up to 251/258 degrees at .050 and a lobe separation of 111 degrees installed at 109 degrees with the same .624-inch lift. It clearly preferred the additional intake timing and tighter lobe separation with a peak power reading of 642 at 6,900 rpm and average torque ranging from 552 to 567 as the EFI system was dialed in.

(Left) Cloyes Hex-A-Just true roller timing set provides adjustable cam timing via its adjusting nut. This made it easy for Borowski builder Dave Lively to dial in the cam for maximum performance. (Center) A Melling Select 10295 LS oil pump was tested with various spring combinations to accommodate the stepped low volume oil galley configuration used in the LS Next block. (Right) Moroso developed a special aluminum oil pan to accommodate the LS Next block. It incorporates 2-inch billet spacers to precisely position the pan in line with the front cover and rear main pan seal. Total pan depth with the spacers is 8 inches. It features internal trap doors and accommodates up to 4.124-inch stroke with most steel rods.

“The torque average increased by 10 lb-ft,” reports Livesey. “At 4,000 rpm it jumped from 484 to 533, It was still up 10 at 5,000 rpm and still up five at 5,500 rpm. Best overall power was achieved at 13:1 air fuel ratio and 31 degrees total timing. And the initial 640 horsepower package also provides good vacuum for the EFI and any vacuum operated accessories.

Moroso’s aluminum pan PN 20144 requires the use of Moroso pickup PN 24144 to provide the ideal pickup location in the 6-inch deep pan sump.

“In all our power and calibration testing we encountered no oiling or bearing issues, even with 28 repeated pulls and oil temperature up to 250 degrees,” continues Livesey. “There were no issues with the block whatsoever.” 

Boost is in the future

“We’re very pleased with the results and the cost to value ratio of this package,” echoes McCaul.  “We like the top-end packages we can use on it and we’re very happy that the new Dart block provides the long term durability we’re seeking for our customers.”

These results were very much in line with their prior thinking and McCaul was pleased  with the performance of the L92 cylinder heads for the naturally aspirated packages. At 640 horsepower the hydraulic-cammed pump gas engine is a sweet affordable player. And with the trouble free LS Next block easily supporting their program, they’re already eyeing an additional bump to 440ci, pricier heads and a 700-horsepower target for an N/A package at a somewhat higher price point.

Rectangular port L92 heads helped contain the cost on the build and eliminated the need to go to LS7 heads to make good power. The builders touched up the 3-angle valve job on the CNC ported factory heads and double checked the chambers for volume.

The cylinder heads are further upgraded with PAC conical 1219x valve springs and the GM rockers are re-fitted with Comp Cams LS Series retrofit trunnion kits designed to convert stock LS Series rocker arms into captured roller trunnions for high-rpm race applications. CNC ported exhaust ports in these heads have proved very efficient in the 500-700 horsepower range.

A more serious jump in power will soon follow when they mate the LS Next blocks with Whipple intercooled superchargers in both under and through-the-hood sizes (2.9 and 4.0L) and Borowski-designed pistons optimized for boost.

(Left) An Edelbrock Victor Jr. L92 intake manifold with 4150 stye mounting flange accommodates most EFI setups. Borowski tested with several different throttle bodies including an FAST 4-port configuration as shown left and a FAST 102mm single-bore throttle body (below). (Right) Borowski’s own polished billet valve covers area fitted with MSD individual coil relocation kit to ensure top ignition performance.

“These supercharged engines will truly be road and track,” says Livesey. “When running high-octane fuel, you can switch pulleys and tune for a big jump in power. With street tune and a low-psi pulley, the supercharger’s vacuum-activated bypass valve provides fuel economy in routine operation but unleashes an instant power surge when the hammer comes down.”

There’s little doubt that LS-based blocks could have easily supported these power levels and mostly without duress in their N/A and low-boost packages. But savvy builders like McCaul hedge their bets with as much backup they can get. The LSN block eliminates the few trouble areas that can arise with a standard LS package. It also opens the door for higher boost that may otherwise be pushing structural limits.

Coated Schoenfeld headers were used in testing and are available separately for various chassis applications, and a complete GM front serpentine accessory drive kit is installed and was in place for all the power testing.


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