We started with an affordable $300 complete engine core of a 2000 GM 5.3L iron-block LS engine, taken from a truck. The pieces that were not needed for our build (intake, injection system, exhaust manifolds, etc.) were sold off, leaving us with about $100 invested in the long block core.

The goal of this build is to create an LS engine that produces around 400 HP, on a tight budget, and with a decidedly “retro” appearance. Basically, we’re taking a 5.3L (   CID) LS engine, and overboring to a final 327 CID, making a “new” 327 Chevy that takes advantage of current technology while stepping back in time to achieve a decidedly “old school” appearance.  Instead of running fuel injection, we’ll set this puppy up with a good ‘ol 4-barrel carb. The block is painted good ‘ol Chevy orange, with a few additional appearance touches that take you back to the old classic glory days of the smallblock Chevy.   We started with a 2000 GM LS 5.3L (Vortec) iron block (originally installed in GM trucks). Instead of changing out everything, in order to stick within a limited budget, we re-used the block, crank, heads, front and rear covers, top valley cover and valve covers. Our pistons are hypereutectic oversized replacements that are actually intended for the 4.8L LS engine. The block has simply been checked for main bore alignment, the cylinder bores oversized to accept the new pistons, and the decks have been kissed for cleanup. The OE crankshaft has been cleaned, checked for straightness and polished. The connecting rods are powder-metal direct-replacement floating-pin versions produced for 2005 and later GM  LS engines. The switch to floating pin design was prompted by complaints of piston noise at cold startup. The only components that we changed (from an alteration standpoint) include the camshaft (we picked a hydraulic roller grind from Crane), pistons and intake manifold. As further dress-up, we also opted for a nifty cast aluminum LS oil pan and coil covers from Holley, and a very cool retro Olds/Caddy twin-snorkel air cleaner from Speedway Motors. Of course, wear-related items were changed with new, including Mahle-Clevite bearings, Hastings rings, Melling oil pump, Melling timing gear setup and Mahle-Victor gaskets and seals. I’ll provide all of the specifics throughout this first and subsequent articles.  

 The OE crank pulley is a tight press fit (no key). GM calls for a special 3-jaw puller. Be sure to locate the puller jaws into the recesses located on the rear of the pulley hub.

After removing the front and rear engine covers, remove the main cap bolts and dislodge the main caps. Remember that a series of 8mm main cap side bolts are featured. Be careful when removing the main caps. These are made of PM (powdered metal) and may provide a snug interference fit to the block. If you encounter main caps that are super-tight, you can use a special "block spreader" tool that gently spreads the block away from the main caps for easier removal.


LS engines (in many of its variants) are plentiful enough today that finding a rebuildable core is not difficult at all. The 5.3L is a great choice for a budget build due to the cast iron block. The iron-block 5.3L isn’t considered a “high performance” engine, so as a result, cores are cheap. We located a complete core (intake to oil pan) locally for only $300. After the owner sold off the items we didn’t need (intake manifold, injectors, engine harness, miscellaneous brackets, exhaust manifolds, etc., he was into the long block core for a mere $100.  .

Once the bare block was hot-tanked and cleaned, all dimensions measured and all corrective machining performed (check main bore alignment, bore/hone cylinders, check lifter bores, square decks, etc.), the block was thoroughly washed and rinsed again. The exterior was then coated with etching primer and moved into our clean engine assembly room for test fitting of components.       


We stripped down to a bare block, and treated it to a hot-tank & wash. This was followed by a magnetic particle inspection for cracks (the LS iron blocks are not known for cracking problems, but it never hurts to check). As we expected, there were no structural flaws. The main bore was checked for alignment, and luckily no correction was needed. Cylinder bores were measured and revealed 0.002” wear. Since we planned to go +0.010” oversize anyway, this was of no concern. Once the cylinder bores were oversize-bored and finish-honed, fresh Clevite cam bearings were installed and we were ready to begin assembly. Prior to the start of test-fitting, we etch-primed and painted the block exterior in classic, “old school” Chevy orange. As I mentioned earlier, our intent here is to take advantage of the technology and performance offered by the LS platform, while creating a “retro” appearance reminiscent of the early 327 Chevy smallblock.  

NOTE: After the block has been machined (boring/honing, etc.), be sure to inspect all female threads for cleanliness. This means making sure that holes are clean (no dirt, crud, etc.) and making sure that no rust buildup is present on the threads. This is especially important for cylinder head bolt holes. The LS features both 11mm x 2.0 threads and 8mm x 1.25 threads (the 8mm holes are at the extreme inboard side of each head, adjacent to the engine top cover). If you need to chase the 8mm holes, it’s no big deal. Just grab an 8mm x 1.25 thread chaser, run it through, blow out the hole with compressed air and you’re done. However, cleaning out the 11mm holes can be a challenge due to the depth of the holes. You’ll need a LONG 11mm x 2.0 chaser (to the tune of about 100mm or longer). Luckily, ARP offers a dedicated 11mm x 2.0 thread chaser specifically for LS blocks, under ARP P/N 912-0011. Don’t even screw around…just buy one. By the way, don’t use a conventional tapered or bottoming cutting tap to clean threaded holes, since a cutting tap can remove thread material, which can weaken the threaded connection. A chaser tap is designed to follow the existing threads, cleaning and removing burrs or other deformations. Essentially, a chaser tap cleans and re-forms the threads. Yes, this means spending more money on dedicated chaser taps, but it’s the only way to do the job right.    

Before any test-assembly takes place, the main caps are fully installed and tightened to specifications. This places the stresses on the block that result from main cap installation. This allows us to final-check main bore geometry and to test-fit our piston rings. Since we planned to use new OE main cap bolts, we followed the GM torque-plus-angle main cap bolt tightening method. In order to achieve accuracy in an efficient manner, we used Snap-On's new electronic torque/angle torque wrench.

The main caps register to the block via cap bolt locations (no registration keyways or dowels). make sure that all female threaded holes are clean before attempting to install the main caps.


We opted to maintain the original stroke (simply overboring to achieve our desired 327 CID). Original stroke is 3.622” (92mm). Since our plan involves hitting about 400 HP, there was no reason to lay out the coin for a new aftermarket crank, since the OE crank is usually good up to about 500+ HP. The crank was checked for straightness (runout), which we measured at a mere 0.0006”. Main and rod journals measured out at 2.5585” and 2.0994” respectively (OE specs are for mains at 2.558 – 2.559”, and rod journals are specified at 2.0991 – 2.0999”). Basically, the only thing we needed to do to the crank was a cleaning, balance and a polish. By the way, crankshaft balancing is a must whenever building any engine, especially a performance engine. Plus, since in our case, we’re changing pistons (piston weight has changed due to larger diameter and flat top design), re-balancing the crank was absolutely necessary.    

Main cap bolts (OE) require a specific torque/angle tightening procedure. Inner bolts (vertical bolts closest to the main bore) are first tightened to a value of 15 ft-lb (first pass), followed by an additional 80 degrees of tightening rotation. Outer vertical bolts are first tightened to 15 ft-lbs, followed by 53 degrees of additional rotation. The smaller 8mm side bolts are snugged to a value of 18 ft-lbs. You must follow the specific tightening sequence during both torque and angle tightening. The advantage of the Snap-On wrench is its abaility to be used for both torque and angle without the need to change tools and waster time. As you approach the pre-set torque or angle, the tool buzzes and vibrates. By watching the display window on the handle, you can hit your numbers with a high degree of precision.

MAIN CAP BOLT TIGHTENING SEQUENCE Perform all torque and angle tightening following this sequence: 1. No. 3 main cap inboard bolt LH 2. No. 3 main cap inboard bolt RH 3. No. 4 main cap inboard bolt LH 4. No. 4 main cap inboard bolt RH 5. No. 2 main cap inboard bolt LH 6. No. 2 main cap inboard bolt RH 7. No. 5 main cap inboard bolt LH 8. No. 5 main cap inboard bolt RH 9. No. 1 main cap inboard bolt LH 10. No. 1 main cap inboard bolt RH 11. No. 3 main cap outboard bolt LH 12. No. 3 main cap outboard bolt RH 13. No. 4 main cap outboard bolt LH 14. No. 4 main cap outboard bolt RH 15. No. 2 main cap outboard bolt LH 16. No. 2 main cap outboard bolt RH 17. No. 5 main cap outboard bolt LH 18. No 5 main cap outboard bolt RH 19. No. 1 main cap outboard bolt LH 20. No. 1 main cap outboard bolt RH .

Make sure that your socket is clean and undamaged (no cracks or burrs). Install and tighten the 8mm side bolts last.

The No. 3 main cap (center of block) features the crankshaft's thrust bearing location.

Use only quality main bearings. The MAHLE Clevite Tri-metal bearings are an excellent example.

Each main cap features small "ears" on one side. Main caps No. 2 through 5 are installed with these extensions facing froward. No. 1 main cap's ears face rearward.   .

Our original crankshaft checked out fine, requiring only balancing and a polish on all journals (seen here prior to polishing)..

Once dimensions were checked, the main caps were removed. New main bearings awere installed into each main cap and block saddle. Royal Purple Max Tuff assembly lube was applied to all exposed main bearing faces. This is a super-slick, super-clinging assembly lube (my personal favorite).

The crankshaft is gently laid into the upper main bearings. Do not rotate the crank until all main caps have been fully installed, as this may accidentally move a bearing shell (or at the very least, this might push a bit of assembly lube onto the main cap mating surfaces).

The main cap bolts are again tightened using the OE torque-plus-angle method. Note: If you opt to use aftermarket main cap bolts or studs, always follow the fastener maker's tightening specifications (this will usually involve straight torque only, without the angle factor). Note that the OE main cap bolt set features a few with stud tips. These are to be located on the outboard side, to accept the windage tray and oil pump pickup.   .

The 8mm side bolts are installed and tightened after the main cap primary bolts are final-installed.  

With the crank installed, crank endplay was measured at 0.0035".


Our oversize pistons were sourced from Federal Mogul (Sealed Power P/N H1132CT, +0.25mm). These are essentially flat-top 0.010” oversize. However, Federal Mogul does not offer rings for this oversize (I’ll never understand that). After a few calls, I did locate the proper size rings from Hastings (P/N 2M4978010). The LS piston calls for 1.5mm top, 1.5mm second and 3.0mm oil ring package.

When checking piston ring end-gaps, each ring must be squared inside the cylinder bore. The Trick Flow adjustable ring-squaring tool makes this a breeze. Adjust it for the bore diameter, insert the ring into the top of the bore, and install the tool. The tool pushes the ring down into the bore by an equal amount along the entire circumference.

Our Hastings +0.25mm piston rings were checked at 0.019" top, 0.018" second and 0.025" oil rails, which was perfectly acceptable, with no file-fitting required. We checked ring fit at each individual cylinder location, and organized each set of rings for each cylinder.

Our rods are bone-stock powdered metal GM units, P/N 12577583, maintaining the stock 6.098” center-to-center length (as mentioned earlier, with floating wrist pins), upgraded with much stronger ARP rod bolts. These rods were used in 2005 and later LS engines, upgraded to floating wrist pin fitments (rod small ends feature bronze bushings). We could have re-used the original rods, but as long as we’re at it, it just made sense to upgrade to the floating pin design. Also, the early LS rod bolts are notoriously weak. Whenever rebuilding any LS engine while using OE rods, always make a point to step up to ARP rod bolts. 

All rods, rod bearings, pistons and rings were organized on our Lista workbench, with each set dedicated per assigned cylinder. Each rod and rod bearing pair were individually test-installed to check for rod bearing clearance and for rod sideplay.

Prior to assembly of rods to pistons, Royal Purple Max Tuff was applied to the wrist pins.     .

Since we're using floating wrist pins, the pins must be secured to prevent them from walking out. Our pistons included tensioned wire clips. These are compressed and inserted into the clip grooves inside the piston pin bores, after the wrist pin is in place.

Ring side clearance was re-checked prior to ring installation. .  

Rings are installed carefully. The oil ring rails can be spiral-wound into place, but the second and top rings must be carefully expanded and located into the their respective grooves. Never bend or twist the upper rings, as you'll permanently distort and ruin the rings.

Once pistons were assembled to rods and rings installed to pistons, each cylinder's package remained organized on the Lista bench prior to final installation. Our clean engine assembly room provides a dust-free environment to keep everything clean and dust-free.

Our rod bearings are MAHLE Clevite, in standard size.     . Original LS rod bolts are known for being a weak link. We replaced the originals (left) with ARP rod bolts. The ARP bolts are much stronger and are shouldered, so they do not require the OE centering sleeves that are used on the OE bolts.  

We compressed the piston ring package using an adjustable Summit Racing ring compressor tool. With the cylinder bores clean and then lightly oiled with 30W non-detergent engine oil, and the upper rod bearing installed and lubed with Max Tuff lube, the rod/piston package is carefully inserted (during each rod/piston installation, the crank is rotated to place the respective rod journal at/near bottom-dead center, which allows easier rod cap installation access).

With the tapered adjustable ring compressor adjusted properly, the piston is easily pushed into the cylinder, with no need to tap/bang with a hammer handle.

With the rod cap saddle clean and dry, the lower rod bearing is installed and lubed with Max Tuff assembly lube.

ARP Ultra Torque assembly lube is applied to the threads and underside of the bolt head on each ARP rod bolt.

Rod bolts were tightened using the Snap-On electronic torque wrench. I initially tightened each pair (on the same rod journal) of rods to 15 ft-lbs. Once the pair was installed on the same rod journal, I then final-tightened the rod bolts to ARP's recommended 40 ft-lb value.   .

Rod side clearance measured out at 0.012".

Our next article will address the camshaft, oil pump, timing set and cylinder heads, so stay tuned. By the way, notice the block color? We painted the exterior in good 'ol Chevy orange. Wait until you see the final product. You're gonna like the retro touches.


While we'll address the camshaft and heads in detail in the next article installment, here's a preview: Our cam is a custom-order steel billet grind from Crane. Our custom cam specs will provide a classic “hot rod” chop and sound. Our cam grind features a tighter lobe separation as compared to LS cams that are designed for use with fuel injection.   


Lobe lift………………………0.324”/0.324” Valve lift…………………….. 0.550”/0.550 (w/ 1.7:1 rockers) Duration @ 0.050”…………... 228 deg. intake; 236 deg. exhaust Lobe separation……………… 110 deg.  


While there’s nothing to complain about with the original casting number 862 aluminum heads (GM P/N 12559862), making them flow much better was a simple task. Total Engine Airflow, well-known for their development of LS cylinder heads, already had a CNC program for reworking the intake and exhaust ports to elevate intake runner volume from the original 200cc to 220 cc; and exhaust ports from original 70cc to 78cc).  The original 5.3L aluminum heads have been CNC ported by Total Engine Airflow to increase runner volumes and flow CFM. Also, the original 1.89” intake valves were replaced with LS1 2.00” intake valves (exhaust valve diameter was kept at the original 1.570” diameter. The 61.15cc chambers were left unmodified. However, the cylinder head decks were milled 0.030” to reduce chamber volume to 58cc.  In conjunction with stock block deck height, stock stroke, stock rod length and our flat-top pistons (the OE 5.3L pistons feature valve reliefs), this produces approximately 11.0:1 compression ratio, as compared to the OE compression ratio of 9.5:1. Because of the increased valve diameters, the stock size 5.3L head gasket slightly hangs into the chambers, so we switched to 5.7L LS head gaskets (which offer a 3.900” gasket bore).  


OE (stock)…………….3.780” Our overbore………….3.790”  OE stroke……………..3.622”  OE displacement……….325.17 CID Our final displacement…326.89 CID  

Formula for determining displacement: BORE DIA X BORE DIA X STROKE X 0.7854 X NO. OF CYLS   OUR DISPLACEMENT: 3.790 X 3.790 X 3.622 x 0.7854 X 8 = 326.89 CID (rounded off to 327)  

 CYLINDER HEAD SPECS            OE                     MODIFICATION

Combustion chamber volume……61.00cc ….…………… 58cc

Compression ratio………………..9.5:1 …………………. 11.0:1

Intake port volume……………….200cc ………………… 220cc

Exhaust port volume……………..   70cc …………………  78cc

Intake valve diameter…………… 1.89” …………………. 2.00”

Exhaust valve diameter…………. 1.55” ………………….. 1.55”

Valve springs: These were changed from the OE beehive springs to Trick Flow Pacoly #TFS-15408 beehive (130 lb @ 1.800” / 318 lb @1.200”). These springs are a bit heavier than OE LS6 springs.   Note: Do not skimp on valve springs by re-using original OE springs. Also, be aware that if using LS6 springs, not all of them feature the same coil-bind height. OE LS6 springs are available in several versions, so you never know what you’re getting. The best approach is to obtain quality aftermarket springs that are consistent.    


CYL HEAD FLOW (CFM)     LIFT                    INT            

EXH 0.100 ………….. 63 ……….. 54

0.200 …………. 128 …….. 93

0.300 …………. 179 …….. 121

0.400 …………. 210 …….. 145

0.500 …………. 218 …….. 163

0.550 …………. 221 …….. 168

0.600 …………. 226 …….. 174  


CYL HEAD FLOW (CFM)      LIFT                   INT           

EXH 0.100 …………..  65 ……… 48

0.200 ………….. 145 ……... 114

0.300 ………….. 215 ………166

0.400 ………….. 254 ………222

0.500 ………….. 293 ………244

0.550 ………….. 306 ………252

0.600 ………….. 310 ………256    


Main bearing oil clearance……0.00198” (spec is 0.0007 – 0.00212”)

Crankshaft endplay…………...0.0035”

Rod bearing oil clearance……..0.0015” (spec is 0.0009 – 90.0025”)

Rod side play………………….0.0120” 

Piston deck clearance…………0.005” (below deck)

Camshaft endplay……………..0.006” (spec is 0.001 – 0.012”)

Crankshaft runout……………..0.0006” (max allowable is 0.00118”)

Main journal diameter…………2.5585”

Main journal taper……………..0.0001”

Rod journal diameter…………..2.0994”

Rod journal taper………………0.00008”

Rod bearing bore dia. …………2.2245”

Lifter bore dia. ………………..0.844”

Camshaft bearing bore dia. 1&5….2.346”

Camshaft bearing bore dia. 2&4….2.326”

Camshaft bearing bore dia. 3……..2.307”

Top ring gap…………….0.019”

Second ring gap…………0.018”

Oil rail gap……………..…0.025”  


Main cap 10mm inner ……………..…..15 ft-lb plus

80 degrees Main cap 10mm outer……………….....15 ft-lb plus

53 degrees Main cap 8mm side bolts……………....18 ft-lb

Rod bolts (ARP w/ARP Ultramoly)…...15 ft-lb initial; 40 ft-lb final

Cam gear bolts…………………………26 ft-lb

Oil pump bolts………………………….18 ft-lb

Windage tray to main studs…………….26 ft-lb

Oil pump pickup to oil pump……………106 in-lb

Oil pump pickup brace to main stud…….26 ft-lb    


If using new OE cylinder head bolts:

11mm x 2.0 x 155.5mm bolts………22 ft-lb plus 76 degrees, plus 34 degrees

11mm x 2.0 x 101.0mm bolts………22 ft-lb plus 76 degrees, plus 34 degrees

8mm x 1.25 x 46mm bolts………..22 ft-lb (these specs based on lubricating threads with engine oil)   

If using ARP cylinder head bolts 134-3609*

11mm x 2.0 x 155.5mm bolts………75 ft-lbs

11mm x 2.0 x 101.0mm bolts………75 ft-lbs

8mm x 1.25 x 46mm bolts………….25 ft-lbs

*Use ARP Ultramoly on threads and underside of bolt heads. (Do not use a different thread lubricant. ARP’s torque specifications are based on the use of their Ultramoly lube, which is included with their head bolt kit).     


 ITEM                                                MFG                                    PART NO.  

PISTONS                                 Sealed Power                         H1132CT (+.25mm)  

PISTON RINGS                         Hastings                               2M4978010  CONN.

RODS                                           GM                                        12577583  

MAIN BEARINGS                   Mahle-Clevite                             MS-2199H  

ROD BEARINGS                    Mahle-Clevite                               CB663A  

CAM BEARINGS                     Mahle-Clevite                            SH18145  

GASKET SET                          Mahle-Victor                              HS54340  

CYL HEAD BOLTS                   ARP                                         134-3609  

MAIN STUDS                            ARP                                         234-5608  

ROD BOLTS                             ARP                                      134-6006

CAM GEAR BOLTS                  ARP                                       134-1003

OIL PUMP                               Melling                                       10295  

TIMING SET                           Melling                                 3-3SRH60SA  

CAMSHAFT                            Crane                        144-HR-228/3241-252-10 4A  

VALVE SPRINGS                Trick Flow                                 TFS-15408  

LIFTERS                                 Crane                                     144536-16

INTAKE MANIFOLD                TBA                                        650 CFM

CARBURETOR                       Holley                                0-82651 Street

HP  FUEL INLET ASSEMBLY   Earl’s                               AT101185ERL  

FUEL PRESS. REGULATOR    Holley                                   12-707  

FUEL FILTER                            Earl’s                               AT230206ERL  

CARB INSTALL KIT                  Holley                                    20-124  

THROTTLE BRACKET              Holley                                    20-88 6LS

IGNITION CONTROL                 MSD                                     6010  

EXHAUST HEADERS                Flowtech                             91836-1FLT  

LS COIL COVERS                      Holley                                   242-1  

OIL PAN  & PICKUP                  Holley                                    302-1  

WATER PUMP                         Tuff Stuff                                1310B  

OLDS/CADDY RETRO AIR CLEANER       Speedway Motors                 92511925  

REAR OIL RESTRICTOR          GM                                        12573460  

FRONT OIL GALLEY PLUG     GM                                        09427693  

(Note: Complete block completion kit is available from Scoggin-Dickey, P/N SDL SPK. This includes cyl. head dowels, trans. Dowels, all block plugs and oil restrictor)    STAY TUNED FOR PART 2 OF OUR LS RETRO BUILD! ***