Little Iron Orphan: A Budget Iron-Block 5.7L LS From A Scrapped 5.3L

Have you ever seen the comic strip Little Orphan Annie? She was a little red-headed girl who found herself involved in many adventures with mostly unscrupulous adults. So it made sense to call our LS engine the “Little Iron Orphan,” as its adventures will probably be similar. Our engine ended its first life as a corroded, cast-off 5.3L that we inherited with the purchase of Orphan’s 6.0L big sister (“You have to take both engines if you want the 6.0L”).

We decided to stretch the little 5.3L block’s boundaries by expanding the stock bore out to 5.7L dimensions. Since the  5.3L, 5.7L, and 6.0L Gen-III engines all share the same stroke, we could easily build a 5.7L on a budget. However, as often happens with best-of-intention plans, problems arose from the outset.

Our block turned out to be nasty and rusty enough to be untrustworthy. We discovered that Summit Racing could ship a block already bored and honed to 5.7L specs, decked, and fitted with new cam bearings and all-new small parts for less money than it would cost to have our local machine shop do the same work. Plus, the Summit block arrived with free shipping in a matter of a few days. That made the decision easy.

This is how bad our used 5.3L was when we opened it up. It had seen water and required destroying three pistons to remove them. Needless to say, we were reluctant to use anything except the crank.

The Short-Buck Short-Block

We’ve never been enthusiastic about the stock LS powdered-metal connecting rods because the fractured cap does not allow easy resizing. We decided to upgrade to a set of pressed-pin, Scat 4340 forged-steel, stock-length rods. We then ordered a set of stock-replacement, standard 5.7L bore (3.898-inch) Speed-Pro hypereutectic pistons and a stock ring set.

Our 5.3L crank was also crusty, so we had our machine shop, JGM, polish it for us. The next stop was to deliver the rotating assembly to our friend, Guy Tripp at SoCal Diesel, to balance the rotating assembly. With information from our friends at Federal-Mogul, we discovered the 5.7L pistons are only 10 grams heavier than the stock 5.3L pistons, so balancing wasn’t an issue. JGM pressed the rods on the pistons for us, and the short-block was ready for assembly.

We priced the difference between having a local machine shop resurrect our rusty block and just getting a 5.7L-bore block from Summit. The Summit piece was less expensive, required less work on our part, and we didn’t have to wait three weeks for the machine shop to do the job. It even comes with new plugs and diverter valve, which we otherwise would have had to purchase. And shipping was free!

Stock LS1 pistons employ a 1.5mm/1.5mm/3.0mm ring package, which is thinner than traditional 1/16-inch top rings, and the thinner LS1 oil rings produce less tension as well. If we were building an all-hands-on-deck naturally aspirated LS, we would have stepped up to forged pistons and a thinner 1.0mm ring package. But for this mild street version, the standard 1.5mm package promised to be good and affordable.

We didn’t spend the extra money for 0.005-inch oversize rings, so we just installed the stock-replacement rings on the pistons and used an ARP ring compressor to guide the pistons into the bores.

New cam bearings can sometimes be tight on a new cam, so we installed the Summit cam (see below) before the rotating assembly. That way we could address a cam bearing problem without having to work around the crank and rods. In this case, the cam slid right in place, so drama was averted.

(Left) JGM polished our crank to remove some surface rust. By adding 0.001-inch tighter clearance Speed Pro tri-metal bearings, we were able to create acceptable main and rod bearings clearances. (Center )When measuring main bearing clearance, always remember to torque the side bolts. The clearance tightened 0.0005-inch when the side bolts were torqued to spec. (Right) We had previously checked the crank end play to make sure we were within spec. At first, we had barely 0.002-inch so we had to sand the leading edge side of the thrust to open up the clearance to 0.005-inch.

We also ordered a Summit dual-row timing set and spent the extra time to degree the cam to ensure it achieved the proper intake centerline. We ended up with the cam slightly advanced at 107 degrees compared to the Summit cam’s recommended installation of 108 degrees ATDC.

Our experience with used LS truck engines is that previous owners tend to be less-than-casual about oil changes. This abuse to the hydraulic lifters means we consider them scrap in a build. We replaced the stock lifters with a new Summit kit that includes new plastic lifter guides and fasteners as well.

To keep a lid on cost, we went with a Speed-Pro stock bore replacement 5.7L piston that is a true flat top and matched it with a set of forged I-beam Scat rods that are stock-length and use a pressed pin. Our new piston and rod package weighed within 10 grams of the original 5.3Lpiston and rod combination. (Right) Scat gave us both a torque spec and a rod bolt stretch figure, but we always use the 0.0045-inch rod bolt stretch gauge figure. This is ARP’s new digital stretch gauge which is very cool.

Low-Buck Top-End

The best way to make power on any engine is to improve breathing. While even stock LS engines are blessed with good flowing heads, stock LS heads can still be improved upon. The best approach would be a pair of TFS cathedral port heads, for example, but these were outside our foster-care budget.

Instead, we talked to Richard Reyman at West Coast Racing Cylinder Heads (WCRCH) in Van Nuys, California. His company offers an affordable porting operation on production 4.8/5.3/5.7L heads which delivers a significant airflow increase.

West Coast Racing Cylinder Heads performed a little port magic on our stock LS1 853 heads. WCRCH used its 5.3L truck head CNC program, which retains the original 2.00/1.55-inch valves. We also had them trim the chambers down from 67 to 65 cc to bump the compression to 10.5:1. Most of West Coast’s CNC work concentrates on the pocket area directly below the seat. This is where 90-percent of the flow improvements will occur if not increasing port cross-section. We’ve made 430 hp on a 4.8L motor with similar work to a pair of 5.3L heads. Do the match on that 4.8L motor and it equals 1.46 hp/ci.

The big difference between a set of 5.3L (852 or 706) heads and 5.7L LS1 (853) heads is the chamber size and the intake-valve diameter. The 5.3L truck heads use a 1.89-inch intake valve, while the 5.7L heads found on car engines enjoy a 2.00-inch intake valve. We initially planned to use 5.3L heads on our Orphan but the combination of the smaller 61cc chamber and flat top 5.7L piston pushed the compression ratio past 11.0:1, which is too high for California 91-octane pump gas.

Instead, we employed a set of stock 853 heads from an LS1 because they have larger chambers and were cheap and available. We reused the stock 2.00/1.55-inch valves but took advantage of the WCRCH CNC porting work. We also had Reyman deck the head slightly, bring the 67cc factory chambers to 65cc. That increases the compression to 10.5:1 using a set of 0.041-inch thick Fel-Pro MLS head gaskets. We felt that this combination of improved port flow with more compression would push the Orphan 5.7L up to a decent horsepower plateau.

Summit recently introduced a line of budget-priced cams for the LS engines so we chose a truck cam with performance specs. We chose the option to include a new Summit lifter kit that includes new plastic lifter guides. We also used a Summit timing set to allow us to degree the cam and ensure it was installed at the proper intake centerline.

The next step was deciding on a camshaft. With a budget to consider, we discovered Summit recently introduced a line of affordable LS camshafts. We decided to push a little harder than our usual conservative approach and landed on the Pro LS Truck cam.

With 226 degrees of duration at 0.050 on the intake and 230 degrees on the exhaust, both sides feature 0.545-inch lift and a 112-degree lobe separation angle (LSA). This isn’t a wild cam by any means, but with the WCRCH ported heads, we expect the peak horsepower number to be up around 6,300 rpm.

Complementing the larger cam is this set of Summit PAC performance beehive valve springs that should eliminate any concern about valve control above 6,000 rpm. The springs allow re-using the stock retainers and locks to keep the cost down. We also added a Summit rocker arm trunion upgrade kit just to give the rockers a little more stability. We did this mainly because the original rocker bearings sustained some corrosion damage.

West Coast Racing Port Flow Numbers

These are WCRCH’s numbers for a ported 5.3L head with a 2.00-inch intake valve but should be very close to the 2.00-inch valve 5.7L 853 head we’re using. Stock intake flow numbers on a 5.7L head at 0.500 lift measure around 226 cfm, so this CNC effort is worth around 40 cfm. On the exhaust side, at 0.500, the stock 5.7L port flows 171 cfm so the improvement is a solid 26 cfm. The bore diameter for these WCRCH flowbench numbers used the smaller 5.3L engine’s 3.780-inch bore size, so the numbers from a 3.89-inch 5.7L bore would be slightly better.

Valve Lift (in.) Intake

Stock (CFM)


Stock (CFM)


Ported (CFM)


Ported (CFM)

0.100 69 56
0.200 139 102 135 100
0.300 192 136 194 143
0.400 217 160 238 177
0.500 226 171 265 197
0.550 245 201
0.600 233 179 250 207

Topping Off the Mash-Up

We topped off the package with an Edelbrock Performer RPM dual-plane intake and a simple 750 HP Holley mechanical-secondary carburetor. This is one of our favorite dyno carbs because they also work very well on the street. The combination would also run almost as strong with a vacuum-secondary carburetor, like a 3310 750 Holley.

We wanted to make sure the Orphan was completely ready to go into a car and that there were no leaks, so we bolted it to our Summit Racing engine test stand, and it was soon ready to make some noise. We pre-filled the oil pump and filter with Lucas 5W-30 performance oil and removed the spark plugs.

We topped the Iron Orphan with a simple Edelbrock Performer RPM dual-plane intake and our trusty Holley 750 cfm HP carburetor. Ignition timing is controlled by MSD’s upgraded 6014 box and new plug wires.

Because we had plenty of assembly lube on the bearings, we tried spinning the engine with the starter motor to build pressure. It took about 15 seconds to produce oil pressure on the gauge. We could have pressure-lubed the engine, but truth be told, we were impatient to hear it run.

With the MSD ignition box hooked into the cam and crank sensors and wired to power, a couple of squirts of fuel was all it took for the Orphan to fire up immediately. We kept the RPM up for a few moments and then set the idle speed and mixture screws — the engine sounded great.

We only ran it for about two minutes or so to make sure everything sounded good since it’s best to break the engine in with a load rather than on a test stand. We’ll have to save the break-in for in-car testing unless we can come up with an excuse to run this rascal on the dyno.

To wrap up the bottom end, we could have used the stock deep truck pan, but they are too deep to use in an early Chevelle or El Camino. So, we opted to spend a little orphan cash for a Holley cast-aluminum pan for early A- and F-body cars.

The 112-degree LSA helps the idle quality a little, and we later discovered it would still idle at nearly 16 inches of vacuum at 900 rpm. With an automatic trans, that would probably drop to around 15 inches or so because it has to drive the front pump. Still, it makes this engine very streetable and would support a power brake booster with no problem.

Our handy engine power-estimation equation tells us this mild 5.7L LS should make around 450 hp and 440 lb-ft of torque. These aren’t headline-grabbing numbers — but that wasn’t the goal with this engine. The Iron Orphan will likely spend its time in between the fenders of an early El Camino that belongs to a certain MMA heavyweight amateur fighter who is currently winning bouts in Iowa. This motor thumps almost as hard as he does!

We bolted the Orphan to our Summit test stand just to make sure it ran with no issues. It sounded good and settled into a nice lope at 16 inches of manifold vacuum at 900 rpm. We think the Orphan should make around 440 HP with 430 lb-ft.

Iron Orphan Parts List

Summit 5.3L iron block to 3.898-inch bore 150157 Summit Racing
Summit Racing LS Truck camshaft 8714 Summit Racing
Summit valve spring kit TFS-16918 Summit Racing
Summit valve lifter guide kit SUM-HTLSKIT Summit Racing
Summit timing set, billet steel G6602R-B Summit Racing
Summit rocker trunion upgrade kit SME-143002 Summit Racing
Summit trunion install tool 141560-IK Summit Racing
Speed-Pro 5.7L hypereutectic pistons H868CP Summit Racing
Speed-Pro piston rings, std bore 5.7L R-1060 Summit Racing
Scat LS1 press-pin connecting rods ICR6100-944P Summit Racing
Speed-Pro performance rod bearings 8-7100CH 1 Summit Racing
Speed-Pro performance main bearings 152M 1 Summit Racing
Federal-Mogul standard oil pump 22443645 Summit Racing
Fel-Pro thin head gasket 041 Left 1160-041L Summit Racing
Fel-Pro thin head gasket 041 Right 1160-041R Summit Racing
Edelbrock Performer RPM intake 71187 Summit Racing
Holley 750 cfm HP carburetor 0-80528-1 Summit Racing
Sealed Power full gasket set 2601880 RockAuto
Fel-Pro intake gasket for carb manifold 1312-1 Summit Racing
Fel-Pro header gasket 1438 Summit Racing
ARP head bolts, early version 134-3609 Summit Racing
MSD ignition box 6014 Summit Racing
Pushrods, TFS 7..400-inch TFS-21407400 Summit Racing
Holley retro-fit cast oil pan 302-2 Summit Racing
Lucas 5w30 oil 10474 Summit Racing
Fram oil filter, Extended Life TG3675 Summit Racing
ARP digital rod bolt stretch gauge 100-9943 Summit Racing

Article Sources

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
Read My Articles

Hot Rods and Muscle Cars in your inbox.

Build your own custom newsletter with the content you love from Street Muscle, directly to your inbox, absolutely FREE!

Free WordPress Themes

We will safeguard your e-mail and only send content you request.

Street Muscle - The Ultimate Muscle Car Magazine

We'll send you the most interesting Street Muscle articles, news, car features, and videos every week.

Street Muscle - The Ultimate Muscle Car Magazine


We will safeguard your e-mail and only send content you request.

Street Muscle - The Ultimate Muscle Car Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

Classic Ford Performance

Street Rods

Classic Chevy Magazine

Street Muscle - The Ultimate Muscle Car Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

  • Classic Ford Performance
  • Street Rods
  • Classic Chevy Magazine

Street Muscle - The Ultimate Muscle Car Magazine

Thank you for your subscription.

Thank you for your subscription.

Street Muscle - The Ultimate Muscle Car Magazine

Thank you for your subscription.

Thank you for your subscription.