Big power LS engines are a key part of our business here at Borowski Race Engines, Inc.  The engines we build are sold worldwide and installed into all forms vehicles for road and track.  In addition, these engines are used in such diverse applications as fan boats and dune buggies.  We are power-adder agnostic believing they all can fill specific niches.  Our LS builds use twin screw and centrifugal superchargers, turbos, nitrous and on occasion, combinations of power adders.  The horsepower capability of some LS engines we ship exceeds the 2,500 hp physical limitation of our engine dyno.  This broad palette of first-hand experience has given us valuable insights into engine block selection which we'd like to share in this video blog.

Great ideas typically spawn a long string of improvements, while bad ideas fade away quickly.  The LS1 engine was a breakthrough in pushrod engine design when it was introduced by GM in the 1997 Corvette.  Some of the key improvements relative to the venerable small block Chevy engine were:

1. Computer controlled ignition
2. Coil on plug design
3. High flowing heads and intake manifold
4. Aluminum block for light weight and better cooling
5. Rigidity from 6-bolt main “Y” design couple with structural oil pan and valley cover

These and other features allowed the LS1 and the subsequent family of LS engines in GM vehicles to be modified so as to produce far greater horsepower than a stock factory starting point.  GM jumped into the aftermarket in 2007 with their LSX block featuring priority main oiling, 6 head bolts per cylinder instead of 4, and a maximum bore size of 4.250 inches among other enhancements.

Prior to Dart’s introduction of the LS Next block in 2013, we had built lower powered LS engines using GM blocks and were aware of their deficiencies in higher power applications that were not adequately addressed by the LSX block (ex. heads lifting, blocks cracking, piston failure due to lack of sleeve support at bottom of stroke, bottom ends failing).  Our intent was to find a way to overcome these issues and as fortune would have it, Dart Machinery was looking at the same set of issues.  We placed a pre-production order for three Dart LS Next blocks when Dart first showed us their plans. 

The most visual feature was that it was skirt-less, not having the “Y” type bottom end, but rather heavy splayed billet main caps.  Other differences are explained in the video.  Months later, the blocks were sold within twenty minutes of delivery to the first customers who walked in our door and saw what we were then carefully inspecting.  One block was subsequently built naturally aspirated while the two blocks were later crowned with Whipple superchargers, one a 2.9L and the other a 4.0L.  All were subsequently featured by Engine Labs magazine (see references for links to articles).

In the intervening years, Dart rolled out an aluminum LS Next and then a skirted version of it so that it could accept OE accessories and oil pans.  They later introduced the LS Next2 option of heavier Ford Cleveland-style main bearings with ½” main studs for mega-power builds.  Going the other direction, the iron SHP LS Next was rolled out in 2017.   The SHP version is skirted and uses a less expensive iron alloy allowing Dart (and engine builders) to compete at a lower price point.  We were first in line for it and received Block #2 from Dart’s president, Richard Maskin, as shown in the photo below.  Most recently, Dart came out with the LS Next SHP Pro which is identical in appearance to the SHP, but is made from the same high nickel alloy as the original LS Next.

As explained in the video, we use GM LS3 (aluminum) and 6.0L iron blocks at lower power levels where we deem them reliable.  The LS3 block offers the light weight and superior heat transfer of aluminum at a cost far below that of any aftermarket aluminum block.  As such, it offers compelling value in its power range.  The GM iron block offers iron’s intrinsically higher strength which allows builds to be pushed to greater horsepower.  How high?  The choice of power adders is a big factor for us.  We are more comfortable with higher power in turbo builds than say in a twin screw supercharger build.  Our concern is the rate of change of torque.  Turbos need to spool up and typically have an upward sloping torque curve.  With their internal bypass and flat torque curve, twin screw superchargers will load up torque on the drive train far faster and expose any weak links.  The videos below show examples of our pushing to what we see as the limits of these two blocks.

As indicated previously, we saw the Dart LS Next block as clearly superior to the GM LSX block and that became our standard for higher power levels.  The skirt-less design added cost and complexity as the block will not accept GM oil pans or accessory drives.  This added cost, but we felt the benefits justified the additional investment.  The skirted versions that were subsequently commercialized resolved this issue, but the SHP LS Next strength has strength limits due to its material of construction.  The recently introduced Dart LS Next SHP Pro is made from the same high nickel iron alloy as its skirt-less counterpart, so that concern has been removed. 

Zeroing in on other common failure modes in high power builds, let’s consider lifting of heads.  As explained in the video, going from a 4-bolt per cylinder to a 6-bolt design is a major improvement in clamping force.   The total number of fasteners goes from 15 to 23 with the major fastener count going from 10 to 18.    Fastener size, type and torque spec also have significant impact.  The GM standard major fastener is 11mm torqued to 70 ft-lbs. The standard Dart major fastener is 7/16” torqued to 90 ft-lbs.  We (and Dart) offer upgrades to ½” head studs with a 105 lb-ft torque spec which raise the clamping force about another 50% over the 7/16" studs.  While we only use ARP head studs, there are higher tensile strength ARP alloys available that we use as appropriate when going larger is not an option.

Moving to the bottom of the standard Dart LS Next block, the mains caps are secured with 7/16” main studs.  One available option in their skirt-less blocks is to switch to a Ford Cleveland-style main which uses ½” main studs.  The mains can be machined to either standard GM LS or Ford diameters for this “LS Next2” option.  In general, we have been using LS Next2 blocks once into the 2,000+ hp range.

So what is our lineup as we climb the horsepower ladder?  Our objective is to provide the most power per dollar without sacrificing reliability in the intended application.  Because there are a lot of known and unknown variables with limits are not clearly defined, we prefer to err on the side of over-building.  In general, the starting points of the discussion are:

1. What is the vehicle and how will it be driven?
2. What are you trying to accomplish (Ex: Run in the 9’s, bragging rights with my buddies for most horsepower, etc.)
3. Street, race, both
4. Fuel type(s)
5. Power adder preference
6. Horsepower target which often turns to a discussion about torque
7. Budget and feasibility of achieving desired goals within budget

The first decision is whether or not to go for an aluminum block.  It is strongly recommended where cooling, weight and weight distribution are major considerations (ex. road racing).  The default choice is iron for strength and low cost.  Our progression for aluminum blocks is as follows:

1. GM LS3, possible upgraded head studs and main caps
2. Dart LS Next skirted aluminum, possible upgraded head studs
3. Dart LS Next non-skirted aluminum with ½” head studs and LS Next2 option

For iron blocks, the progression up the horsepower ladder is as follows:

1. GM 6.0L block, possible upgraded head studs and main caps
2. Dart LS Next SHP, possible upgraded head studs
3. Dart LS Next SHP Pro, possible upgraded head studs
4. Dart LS Next with ½” head studs and LS Next2 option

Neither this writeup nor the video were intended to be comprehensive.  Our opinions are the result of our many years of engine building experience but are still only our opinions.  Nevertheless, we hope that this information provides you with some additional insights and allows you to make more informed choices when you are thinking about buying your next LS block or engine.

References

1. Borowski Builds Mild-Manner 427 with LS Next Block
2. Borowski Built Blown 427 Engine with Dart LS Next Block
3. Supercharged Borowski-Built Dart LS Next LS7 Screams Money