How to Build an LS79 Engine - A Modern Classic

We take a classic displacement combo and modernize it with LS technology

Patrick Hill Mar 28, 2014 0 Comment(s)
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In the midst of a brainstorming session with AntiVenom Performance’s Greg Lovell, we started talking about LS engine builds and how everything seems to be the same, with the most common two being a 408-inch build or a 346-inch combo. Yes, there are 427s, LSX 454s, RHS-based motors, etc, but they aren’t as common as the 408 or 346.

Looking at the available displacements and combos of factory LS motors, we started comparing that to the combos you can build on the Gen I platform. At some point, we started talking about the 327 and how it was the top dog for a long time. Even after the 350 assumed king of the mountain status, the 327—with its short stroke and large bore combo (3.25 stroke by 4.00-inch bore)—was widely popular. It would rev to the moon, but the big bore allowed it to swallow a lot of air.

We compared that to the closest modern equivalent, the 5.3L Gen III truck motor. The 5.3 uses a 3.78-inch bore, combined with a 3.62 stroke, for a displacement of 325 inches. It’s a strong performer in its own right, but more on the torque side for its truck application. Then we started thinking about its little brother, the 4.8. It uses the same bore, but with a shorter 3.27 stroke, just a smidge longer than the original 327. That led us to consider the larger 6.0L truck engine and its 4.00-inch bore.

With the wheels inside our brains really spinning, it hit us: What would we have if we combined the 6.0L block with the 4.8 crank? A 4.00-inch bore combined with a 3.27 stroke crank would give us a displacement of 329 ci. We’d essentially have a duplicate of the old 327, but with all the modern design and capability of the LS platform, using off-the-shelf parts!

We know, a lot of people are thinking we’re crazy here. Why build smaller instead of larger? Well, the simple reason is, insatiable curiosity. We wanted to see what the power would be like from a classic bore/stroke combo, using the superior airflow of an LS head.

After hitting the parts catalogs for several companies, we put together our shopping list and started getting everything together. This story will focus on the parts going into our recipe, and putting it all together. Stay tuned to a future issue of Super Chevy, where we’ll be bolting this bad boy to the engine dyno and seeing how much power it can make. Everything we used is listed in the parts list below, along with the corresponding prices through Summit Racing, or the specific manufacturer if not carried by Summit.

Truck Engine Block 12140 2/41

01. The starting point of our build was a 6.0L truck block, PN 12140 from Summit Racing. It comes fully cleaned, machined with a 0.030-inch overbore, and prepped for use with cam bearings and main caps installed. The 4.030-inch bore will give us a displacement of 334 ci, only 3 inches more than a Gen I 327 with a similar overbore.

Ls Engine Main Cap 3/41

02. One of the strengths of the LS series engines are the six-bolt, cross-bolted main caps. These give the bottom end enormous strength, even in high-horsepower applications.

Ls Engine Crank Thrust 4/41

03. Another aspect that gives the LS strength and durability is the location of the crank thrust, here at the center main bearing. On Gen I engines, the thrust is located off the rear most bearing. This means less wear and tear on the crank and its bearings.

Clevite H Series Bearings 5/41

04. For our main bearings, we went with Clevite’s H-series coated bearings. Developed primarily for the brutal rigors of NASCAR racing, Clevite’s Tri-Armor coating offers excellent lubricity and reduced friction, while adding protection against engine damage in a low oil pressure situation. For the rods, we went with Sealed Power’s Duroshield Competition Series bearings. The coating’s hydrophilic matrix actually bonds with the bearing material, absorbing oil for reduced friction and better lubricity.

O Reilly Crankshaft 6/41

05. Our crankshaft is a reconditioned, factory 4.8L, 3.27 stroke crank we picked up from O’Reilly Auto Parts. It came with a 0.010-inch undercut on the main and rod journals, so we ordered our bearings accordingly.

Main Cap Bolts 7/41

06 To further strengthen our bottom end for current and future testing, we pitched the stock main cap bolts for a set of ARP high-strength main studs. Main studs not only provide more main stability by preventing them from “walking,” but they also exert less stress on the block threads, which helps to extend block life—especially on aluminum blocks.

Arp Main Studs 8/41

07. You also get a more accurate torque reading off of a stud than a bolt, which can affect bearing clearances in some cases.

Wiseco 2618 Alloy Slug Piston 9/41

08. For pistons, we went to Wiseco for a set of forged 2618 aluminum alloy slugs. They feature a similar to stock but a bit heigher pin height, Wiseco ArmorGlide skirt coating for reduced friction and wear, and offset wristpins for cold-start noise reduction. Wiseco also cuts them with LS multifit valve reliefs, compatible with cathedral port and square port cylinder heads. A nitride steel top and Napier second ring package allow for the best sealing, power, durability, and reduced oil consumption. The ring land thickness is maximized to withstand high levels of boost and nitrous. We went with a compression height of 11.0:1, the same as an LS7.

Ring Gaps 10/41

09. Greg Lovell, owner/operator of AntiVenom Performance in Seffner, Florida, assembled our engine. He set the ring gaps at 26 top and 28 middle, giving us the option of applying nitrous to our LS79 later down the road.

K1 Technologies H Beam Rods 11/41

10. For rods, we went with K1 Technologies forged billet H-Beam rods in a 6.390-inch length.

K1 H Beam Rod Height 12/41

11. Why such a long rod? Combined with the heigher pin height of our pistons, this will not only give us an excellent rod/stroke angle but an enormous amount of dwell at top dead center, which means we’ll be able to maximize the amount of time the combustion process has to take place, along with transferring the most energy from the piston to the rod on the down stroke.




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