All LS series camshafts are of the roller style. The LS series of engines utilize a camshaft timing sensor. To provide a signal to the sensor, 1997-2004 LS engines feature a machined reluctor on the camshaft, located immediately in front of the No. 5 main cam journal. Camshafts from 2005 and later eliminate this reluctor, with cam timing picked up at the cam sprocket.
An incorrect rumor has it that when using the stock valve train geometry, the safe maximum camshaft lift must be kept to 0.570″, since the rockers begin to dig into the valve tips beyond that lift. However, Katech’s Newman told me that this isn’t true, since World Challenge race engines that they’ve built typically feature as much as 0.595″ lift with no problems.
By the way, standard LS series OE rocker arm ratio is 1.70:1. The LS7 features 1.80:1 rockers.
All LS heads feature PM (powdered metal) valve seats and powdered metal guides (this PM formulation provides the lubricity of bronze and the longevity of cast iron guides).
All LS1, LS6 and LS2 heads feature tall cathedral-style intake ports. The LS7, L92 and LS3 heads feature rectangular intake ports.
All LS heads, with the exception of the LS7, feature as-cast chambers and ports. The LS7 heads feature CNC-machined chambers, intake ports and exhaust ports.
According to Katech, all cylinder heads within the LS family are physically interchangeable among blocks, with the exception of the LS7 heads. The LS7 cylinder heads cannot be mounted to other LS blocks, as the wider valve layout would result in valves contacting the bores. Also, the L92 head cannot be used on the LS1. Valve clearance must be verified before performing any head swap.
A variety of OE Gen III heads are available, including an iron small port (initially used on the 4.8L truck engine), the LS1 aluminum head, the LS6 aluminum head with 63cc chambers, the LS4 aluminum head with 67cc chambers and LS6 heads with larger ports and larger chambers.
All LS series (Gen III and IV) engines feature a firing order of 1-8-7-2-6-5-4-3. This represents four cylinder swaps as compared to the standard (Gen I and Gen II) smallblock/bigblock Chevy order of 1-8-4-3-6-5-7-2.
All OE threaded fasteners in the LS series of engines are metric. There are no imperial-format (inch) fasteners anywhere in the original-equipment build.
All OE cylinder head bolts, main cap bolts and rod bolts require torque/angle tightening.
There are also no NPT threads found anywhere (water jackets, etc.). Instead, straight metric plugs that featured that use O-ring seals.
Some engines feature solid stems, while others feature hollow, sodium-filled exhaust stems. The LS7 uses titanium intake valves and hollow sodium exhaust valves.
All LS series engines feature a roller lifter, and all feature a 0.842″ lifter diameter. Instead of using dogbones or metal finger-trays to locate the roller lifters (to prevent lifter rotation in their bores), special LS-only composite plastic “lifter trays” are used. These trays each hold four lifters. The cylinder block features a large recessed area above each set of four lifters to accept these trays. During assembly or disassembly, the lifters are held by the trays, allowing a complete set of four lifters and their tray to be installed or removed as a set (lifters and tray together).
All LS series rocker arms are semi-roller type, featuring a trunion bearing at the pivot. All LS rockers are interchangeable for intake and exhaust except L92, LS3 and LS7 rockers. LS7 rockers are unique, as the intake rocker features an offset, and the LS7 rocker ratio is higher at 1.80:1, as opposed to 1.70:1 for all other LS engines.
CYLINDER HEAD GASKETS
Early LS engines featured composite type cylinder head gaskets. Around 2002, GM switched to MLS head gaskets.
All remaining gaskets throughout the engines are formed elastic seal type gaskets that are reusable (depending on condition of course).
OE stock pistons are hypereutectic type. Aftermarket forged pistons are readily available from most piston makers. Depending on the specific crank, LS type piston No. 8 may require a narrower profile at the pin bosses in order to clear the crankshaft reluctor wheel (used for picking up crankshaft timing). This is especially important if a stroker crank is being used. Piston deck height (LS1) is 0.008″ above deck.
All LS series heads feature beehive-shaped springs (these feature smaller diameter upper and lower coils for superior damping of spring harmonics). All OE spring retainers are steel, even in the LS7. This single beehive spring design eliminates the need for dual springs, and also allows the use of smaller and lighter retainers.
All LS rods are constructed of forged powdered metal (PM) with cracked caps, with the exception of the LS7, which features forged PM titanium connecting rods.
While the standard smallblock/bigblock Chevy engine featured an offset connecting rod, the LS series features on-center connecting rods (pin bore in relation to big end bore). DO NOT use offset connecting rods in any Gen III engine!
According to Katech, the OE rods are surprisingly strong, while the primary weak point is the rod bolt. Changing to high performance aftermarket rod bolts is recommended. At this point in time, there are plenty of aftermarket forged rods from which to choose, to provide even greater durability than the OE PM rods. The OE rod bolt is 9mm, but Katech offers a 10mm rod bolt to work with OE rods.
According to Newman at Katech, the LS6 will safely over-bore to the same diameter as the LS1, but the LS6 features a sturdier engine case and is a better choice for overboring than the LS1. Newman noted that the larger-displacement LS2 is a less-expensive and superior block than either the LS1 or LS6, and offers much more interchangeability with LS6 OE production parts. Confusing, isn’t it? Welcome to the LS.
How large a displacement can you easily obtain by increasing bore diameter and stroke?
According to Katech’s Newman, the LS1 or LS6 (originally 345 CID) can be sized to a max of 414 CID using a 4.000″ stroke. The LS2 (originally 364 CID) can be easily oversized to 427 CID max as well. Newman noted that 414 CID is the biggest you can go with a dry sleeve on the LS1/LS6. The LS2 can go to 427 CID with a dry sleeve.
Modifications intended to achieve greater strength and durability include changing to forged crankshafts, connecting rods and pistons, billet main caps, replacement connecting rod bolts, the use of head and main studs and oil pump modification, among other tricks. Oil pump mods include disassembly, deburring the pump inside and out, porting the oil entrance, polishing the pressure relief section and reassembly.
Editor’s Note: The majority of the information presented here was graciously provided to us by Katech Performance. Katech has been around for over 30 years and has built a vast array of championship-winning race engines. Katech has also been closely involved with GM during the development of the LS series of engines, and has developed an extremely wide range of performance engine components for this engine series.
I would like to extend our sincere appreciation to both Caleb Newman and Jason Harding at Katech Engine Development for their courtesy, time and expertise in helping to prepare this information for our readers.
Now that we’ve provided an overview of the LS engine family, it’s time to get our hands dirty once again. We’ll soon begin to build a special LS project engine during 2008 and rest assured that we’ll supply all of the details as we go, with a dyno run at the completion of the build.