Project V8 RX-7: Part 2 – Inside the GM LS3 E-ROD Crate Engine


LS3 E-RO crate motor
Our nice new LS3!  Drool!

Let’s talk a little about the LS-3 engine.  For sure pushrods or not, this is a world class state of the art engine.  Gone are the days when the iconic but old small block Chevy stood for Brigs and Stratton like engineering from the 50’s, clearances measured with rulers, heavy cheap metals, lameo stamped sheetmetal and plastic components with stone like weight.  The LS is a distant relative of the old small block.  A total clean sheet of paper design, the LS only shares bore spacing with the small block. The new LS motor’s block is cast from 319 alloy heat treated to T5 level that at 107 lbs weights 53 lbs less than the cast iron lumps that used to stand for Chevy power.  The block casting uses an unusual combination of investment casting dies with traditional sand cores which reduces porosity and gives closer to net shape and more precision than traditional sand casting techniques.  Even pushrods are a smart choice for a hybrid; we will talk about why in future installments of Project RX-7.

LS3 crate engine
The LS3 is a surprisingly small and compact making it a good candidate for swaps into smaller Import Chassis.

GM must have benchmarked Japanese OEM and race motor engine design when developing the LS motor.  The old small block had crude and wimpy two bolt main caps.  When modding a small block, this was an area of concern, flexing caused the parting line of the main caps to havefretting damage.  This caused bearing, friction and durability issues.  When rebuilding a small block the main bores were often distorted and most blocks had to be resized.  The old small block’s structure was also prone to flexing which caused head and ring sealing issues.  A common trick was to fill the block up with epoxy or even concrete “block rock” to stiffen things up.  Aftermarket 4 bolt steel main caps and girdles were often used to fortify a racing small block.

small block chevy
The Granddad of the LS, the GEN 1 small block Chevy.  An iconic motor, the small block is probably the most popular to mod engine in the world still nearly 50 years since it was first conceived.  The engine is nothing like the modern LS, sharing only bore centers.

The heart of an engine is the block and the LS has a state of the art one. The new LS block has deep skirts meaning that the block extends past the centerline of the crank.  The main caps are beefy billet steel and are bolted to the block by six bolts, much like many Japanese and designed for racing engines.  The deep skirts and cross bolted mains makes the LS bottom end an order of magnitude stronger than the old small block Chevy despite being much lighter.  The block’s bores are siamesed which means they touch each other.  This helps improve the block’s structure.  The advanced casting techniques also means that the block can have many complicated features in external and internal geometry like reinforcing ribbing on the outside for stiffness and generous water passages on the inside for better cooling.

LS3 Blown up
The LS3 does not share a single component with the small block Chevy.  It is engineered using modern world class features that we will discuss.


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