Building a 5.3 LS for a Dirt Late Model LS Racing Class: An Interview, Dyno Results & Engine Parts List

It’s no secret that racing a Dirt Late Model has become expensive over the years—which, if we’re being frank, means it has become out of reach for many grassroots racers. 

Ray Seifert feels the same way.

He and his family own Midway Speedway in southern Ohio. Ray fondly recalls that, years ago, the Late Model class often had 35 competitors a night—but $60K engines are simply too expensive for a lot of people to go racing. The Limited Late Models with their CT400 “604” sealed crate engines were a partial solution, but $9,800 for a 410 to 420 horsepower long block is still a hurdle. 

Another issue is maintenance…if a race engine develops a problem, fixing it can take a while. 

So What Are a Racer’s Options? 

Ray believes the answer lies in a junkyard near you. The 5.3 iron block LS truck engine has been in production in various forms since 1999. In fact, these engines are known to outlast the trucks they came in. They are durable and capable of a lot of power with a few basic modifications. 

So what kind of power are we talking about? A Box Stock(!) 200k mile 5.3L with a special Summit Racing Pro LS cam, LS6 springs, and headers made 465 horsepower at 6,900 rpm. 

The heads had never been off and it shrugged off 41 pulls on the dyno like nothing.

Keep scrolling and we’ll get into the nitty-gritty of the engine build, complete with a detailed parts list at the bottom—if the idea of plunking an LS into a dirt late model chassis appeals to you…

…Which if you’ve read this far, we’re guessing it does.

Why Not Ditch the LS EFI & Run a Carb?

Sure, throwing on a carb and intake combo with an MSD 6014 Ignition box is one option—but believe it or not, that’s the more expensive route here. Admittedly, the Gen. 3 Truck intakes aren’t known for making great power with their 78mm throttle body, yet they make great torque and keep the rpm range in a very practical sub-7,500 rpm green zone.

Tuning electronic injection can be a little tricky, so the simple solution for Midway’s LS class is what’s known as a “Canned Tune”. 

Essentially, with the limited modifications allowed in this series, ECUs are handed out at the track or flashed with the same tune. They are dialed in with 13:1 Air/Fuel and an aggressive timing map optimized for pump gas. 

In other words, if a racer were to skirt the rules and produce more power, the result would be melted pistons!

But even if this sounds like fantastic opportunity for grassroots Circle Track racers, a lot of folks are unfamiliar with the LS platform—so if you want a good primer on how the Gen 3. LS can be built for competition on a budget, keep reading and we’ll give you the lowdown.

Our LS Engine Hits the Dirt

Starting with a Gen. 3 iron LS engine block sourced from a scrapyard, our test engine received a modest amount of parts from the Summit Racing LS performance parts portfolio, each one chosen precisely to meet the spec requirements of this class. We’ll give you more engine details along with a complete parts list at the bottom of the article but, as we’ve mentioned, the end result was a reliable 5.3L LS powerplant that made well over 450 horsepower in a very useable rpm range.

More importantly, now that the engine is done, it’s gone into the chassis and is getting tested on the 3/8-mile banked oval red clay track at Midway Speedway.

After seeing it in action, the results are already impressive (we’ll give you the numbers, keep reading), and we’re excited to see how this LS Dirt Late Model class will evolve in the future—particularly since, outside of the block, pretty much all the parts were sourced from right from the Summit Racing Circle Track catalog.

An Interview with a Dirt Track Racer Jerry Marolt

Obviously we’re looking at this endeavor through the Summit Racing lens, so I spent plenty of time talking to fellow drivers and builders about the viability of this new class.

One racer in particular is my new pal Jerry Marolt—he gave us some insight into his chassis and engine combo.

Check out the interview below.

What Attracted You to the LS Late Model Series?

“So 30 years ago, I got into street stock racing. And, I went to college. I’m an aircraft technician by trade. I work on corporate jets, and, my son just finished college, and racing late models on the dirt was a dream of mine.

“My dad used to race back in the days of old Flatheads—this is a 30-year dream come true. To be able to buy a late model chassis, a used one, and take a junkyard LS engine and go out there and compete—it’s incredible.

“You can build one of these cars for, maybe, five or six thousand dollars. That’s unheard of.”

Tell Us About the Chassis.

“It’s a 2007 Boss chassis made Toma Johnson. Tracy Fritter used to own the car and race it. He’d done extremely well. And, yeah, we’re going to do a little updating.

“A lot of these older chassis, they get outdated, and everyone wants the latest and greatest. That’s what makes it great for this series. You can pick up a used chassis…1,500…3,000 dollars.

“I’ve got five grand in this, but this chassis is in great shape. It’s been sitting for a long time, but guess what? We’re given her a new life.”

What’s the Story on the Engine?

“The power is, I figure, right now pushing 450 to 475 horse—with a junkyard truck engine!

[Laughing] “It’s got 120,000 miles on it right now.

“I just pressure-washed the inside and the outside [laughing again]. Factory intake, factory throttle body—I’m a builder, but it’s just so easy to get these engines to work. “

What’s the Future Hold for This New LS Class?

“I really appreciate Summit Racing for doing all this stuff for us. Because I think, by next year, you’ll have 25 of these cars out here.

“A lot of guys out there are looking at $12,000—for just the engine.

“I’ve got $400 in the engine, with a $259 cam and $72 valve springs!”

***

Summit Racing 5.3L LS Dirt Track Race Engine Dyno Results

At a recent dyno run, the engine made 465 horsepower at 6,917 rpm. In fact, it broke 450 hp at 6,300 rpm, and those numbers continued to rise until it hit 7,000 rpm, before beginning to drop.

LS6 springs don’t have a lot of seat or open pressure, and we spiced the lobes up a tiny bit from standard fare knowing these would be used in actual race cars with spring maintenance—we’ll see how long they last. 20 nights? 200 nights? They should last essentially forever, but we’ll see.

All told, with the car’s overall weight, with driver, being around 2,300 pounds, it’s a combination that will be very, very exciting on the dirt this summer

Understanding the 5.3 LS Series Engine Requirements

The Midway Speedway LS class requires a common Gen. 3 5.3 Iron block LS engine in a Dirt Late Model Chassis. As we’ve shown, even a high mileage engine with a Summit Racing Pro LS CT 5.3 Spec Cam and spring kit can make over 460 horsepower without a trip to the machine shop. 

This includes the factory truck intake and 78mm throttle body, Midway Speedway’s spec tune in the original engine ECU, and Summit Racing’s A, B, or C 4-into-1 spec headers, available for most of the common chassis designs you’ll find on the track. 

This combination works together to limit the allure of cheating—all without the increased expenses required to compete at a reasonable level.

How to Identify an LS Engine to Find One for This Class

Ready to head to the salvage yard and start turning wrenches?

OnAllCylinders has a handy LS Engine Identification Guide that’ll help you determine what engine you might have, but the easiest option is to look for a T or a Z in the 8th character of the VIN:

• If the 8th digit is a “T” you have a LM7 LS Engine
• If the 8th digit is a “Z” you have a L59 LS Engine

Those are two 5.3L Gen. 3 iron block engines, the LM7 and its flex fuel cousin, the L59. These two span 1999-2007 and used blocks can often be found for just a few hundred bucks at your local scrapyard (the one Summit Racing used was purchased for just $600).

As opposed to the later 5.3L engines, these feature an all-iron block with 7.7cc dished pistons and 61cc chambers, 1.89 in. intake valve Cathedral Port heads. These are mandated for the class, because Gen. 4 LS engines feature flat top pistons and heads with 2.000 in. intake valves—increasing cost while reducing reduce parity.

To save even more money, these Gen. 3 engines aren’t saddled with VVT or AFM (systems that require removal/deletion kits to run reliably in a performance environment).

Building Your Own LS Dirt Track Spec Engine

This next section covers the basic things you’ll need to install a Gen. 3 Iron block LS into your Late Model Chassis.

Your chassis may be equipped with oil and fuel lines along with cooling system already and easily adapted. Once your chassis is equipped with the proper fuel/cooling/oiling system, running costs are low. We’ve also included basic durability modifications to extend life such as LS2 timing chain and damper, a trunnion kit for the rockers and the Melling 10296 oil pump to support 7,000+ rpm operation without cavitation.

But before we go much further, it’s absolutely worth mentioning something:

An engine like this will work equally well in a Circle Track car, a Bracket Car, Drift Car, Hot Rod, or Musclecar retrofit!

So if you’re just looking for a cheap way to propel your project car with a potent, reliable LS powerplant, this recipe is a good one to follow.

Internally, the only upgrade allowed is a SUM-8735R1 camshaft and matching springs. It is specifically designed for this class with an economical price ($259 at the time of this post). It has a 234/248° duration with 113.5° LSA and 3.5° Advance. This cam is the largest that can be run without piston fly-cutting (which isn’t allowed). It’s designed around inexpensive and proven SUM-174002 LS6 valve springs. This cam and spring compliments the intake manifold to produce great power in the 5,000 to 7,000 rpm range reliably. 

It’s often said that a car will only go as fast as your wallet can open. And that’s where this new class shines. Consider the points below—and how they’re a passive deterrent for anyone tempted to out-spend their competitors.

• A 7.400 in. pushrod length removes the benefit of expensive limited-travel hydraulic lifters.
• Heads are limited to factory 1.890/1.575 in. valve sizes and a machined valve job that doesn’t extend into the bowl more than .500 in. without any hand blending. A 60cc chamber is no more than a clean-up cut at most.
• A 0.051 in. minimum head gasket thickness with a maximum of +0.006 in. positive deck keeps compression at practical 9.5:1
• A maximum 0.005 in. hone (3.785 in.) is all that’s ever required to bring these blocks back into shape. 
• You can run a cast or hypereutectic piston with 1.5, 1.5, 3mm conventional ring package.
• The factory 3.622 cast crank is plenty strong. A Gen. 3 or 4 connecting rod is up to the task without modification.

Dirt Track LS Engine Upgrades

• LS Spec Engine Cam Swap – LS engines do not require the oil pan, heads, or even the intake manifold to be removed to swap cams. Simply pull the valve covers, remove the rockers and pushrods, rotate the engine 720 degrees to move the lifters to the top of their trays, slide the old cam out and the new cam in—then put it all back together. Worn lifter trays may not hold the lifters in place, a simple way to remedy this is to roll the engine upside down on the engine stand to keep the lifters from sliding down until you slide the cam in. The front cover gasket set is usually replaced. A front seal is sometimes replaced, but often not. A new damper bolt is required, because the original is one-use only.

• Reliability Upgrades – While factory pushrods can be reused, a set of one-piece 0.080 in. wall 5/16 7.400 in long pushrods are recommended. It’s also recommended to update to the LS2 chain with thicker links and Trick Flow LS2 Timing Chain Damper adapter to prevent timing chain whip. The cam bearings are generally worn. A Summit Racing 0.005 in. align-honed timing set tightens up the chain. Most engines have well-worn rocker trunnion bearings. Replacement is highly recommended. Kits are available, but many just buy rockers with the trunnions already installed.
  
  Finally, LS engines had steam crossovers in back AND front in the first years. If not already equipped, a front crossover line along with line to the water pump inlet via a modified hose coupler helps cooling.

• Fuel System – Early LS engines ran a single line from the tank to the fuel rail. An external inline pump is used and it runs to a C5 Corvette Filter/Return Regulator. Summit Racing’s combo kit includes much of this, but you will need the -10 to -6 AN adapters at the tank and the -6 AN to fuel rail adapter at the front. As an added bonus, you won’t need big lines and pumps—which helps save you even more money.
  
  L59 Flex Fuel injectors are required to be run in these engines. The LM7 injectors don’t support the power. The tune is based on these injectors characterization tables to ensure the tune stays consistent. Have your injectors cleaned at minimum—but do not buy off-brand injectors! They are rarely correct. Instead, use Delco or Delphi to ensure proper fueling.

Side Note: These engines run fine on 89+ octane with their 9.5:1 compression, so E85 hasn’t shown to be a benefit in power. 

• Oiling – Many chassis already include a remote oil filter housing. The LS makes this conversion easy with an in/out to the oil cooler on the engine block itself. A factory oil pump can be used, but and a Melling 10296 oil pump doesn’t cavitate at 5,500+ rpm like the factory pump.
  
  A Champ pan with kickout and pickup is a quality upgrade and allows the engine to be mounted lower. As an added bonus, the pan we spec out in our parts list below comes with two -10 AN fittings welded to the pan rail over the holes in the block for the oil filter. The front fitting goes to a remote oil filter and/or oil cooler and the back fitting returns the oil to the block—eliminating the need for an extra filter block-off plate.
  

• Crankcase Breathing – Worn LS engines called upon to make big power at high rpm will have blow-by. A catch can is one option, another is open vents and filters. Using two driver’s side factory valve covers with hose barbs PLUS a LS3 vented valley tray provides three outlets to run to a catch can. A step up in volume is a SUM-440368 oil cap with a MEZ-WA16175S -16 AN to 1-3/4 in. hose barb adapter and K&N KNN-62-1470 crankcase vent filter.
  
  If you want something a bit fancier, SUM-440550B and SUM-440555B match and have barbs on each cover and commonly used with ICT Billet Coil relocation brackets such as ICB-551532.  Vented Gen. 4 LS3 Valley covers have become expensive, so one simple option is to drill and tap a Gen. 3 cover for a 90 degree 5/8 in. NPT fitting SUM-221104. If you prefer AN fittings, SUM-440821 covers have two -12 AN locations at either end and are compatible with D510C and D514 coils. 
  

• Electronics – A factory harness and computer (with the Midway spec tune uploaded) can be used. Many aren’t comfortable with splicing or cutting wires, so a Top Street Performance stand-alone harness is commonly used. The current spec one is for a 2002 Camaro with T-56 and cable throttle body. Sensor, coil, and alternator locations are clearly labeled. The VSS (vehicle speed sensor) won’t be used. EV1 to EV6 injector adapters are required at this time. An IAT (Inlet air temperature) breakout harness removes the MAF sensor entirely as the engines are tuned on Speed Density. A replacement two-wire temp sensor is simply installed in the intake core plug or air inlet tract. (Note: To make this even easier, a new harness will have these connectors built in.)
  

• Air Intake – The Truck manifolds and mandated 78mm drive-by-cable throttle body work well with a Spectre Coupler and their memory air duct hose. It makes routing easy and allows the filter to be placed in a clean area.
  

• Headers – Summit Racing has partnered with Beyea to create three part numbers that fit the majority of all late model chassis. These 4 into 1 headers are American made, affordable and are right on the shelf and include the 02 sensor bungs for 2002 Camaro 02 sensors. O2 sensor wiring extensions give extra slack to route your sensor wires safely. 
  

Dirt Late Model LS Spec Engine Parts List

The Allure of LS Dirt Track Racing

Engine builders and racers are always looking for an advantage—that’s to be expected and part of the fun, but the gains will be small if any. To Ray’s point, the goal is to encourage racers with a low cost of entry, ease of repair, and good raceable power to ensure well-heeled racers won’t run away with the class.

In other words, 465 horsepower in a 2,300 pound car makes this a driver’s race.

So if you have a Late Model chassis collecting dust, this is your chance to run again. In most cases, selling off your small block stuff more than offsets the cost to put an LS in your chassis. 

Is racing ever cheap? Maybe not, but making 465 horsepower for—at the time of this article—$332 over and above the cost of a junkyard 5.3 is as good as it gets. 

***

A special thank you to Ray and Chris Seifert, along with AJ and Terry Humphries, for working with us at Summit Racing to create the bones of this new class. You’ve done a great service and we are proud to be a part of it!