We're using a 7/16-14 thread...
We're using a 7/16-14 thread tap installed into a battery-operated drillto clean all 34 cylinder-head bolt holes to remove crud and old threadsealer. Set the drill torque load to the medium setting to avoidbreaking the tap. Then we use compressed air to blow out all of the boltholes. This is also a good time to check the condition of all the boltthreads before the block is assembled.
Our Project Shark Attack '79 Corvette is beginning to take on its newpersona, and we'll cover our 383 engine build in this installment. Wementioned previously that the L98 cylinder block was cracked in thelifter-valley area and we hoped we'd be able to repair it.Unfortunately, it was so badly damaged that we needed another cylinderblock. Fortunately, we had another four-bolt-main (roller-camshaft)truck cylinder block left over from an earlier project. Sometimes wewonder why we keep all those old parts lying around. Now we know.
We had stripped the replacement four-bolt main cylinder block ofinternal components before storing this engine block. The freeze plugsand cam plug had been removed for cylinder-block cleaning. The block hadquite a bit of rusty sediment below the freeze-plug area that requiredattention before the block was sent out to be cleaned. Cast-ironcylinder blocks are chemically cleaned with an alkali-based hot-waterwash to remove grease, oil, and metal particles after boring. The alkalidoes a good job of basic cleaning, but it will not loosen the rustsediment that accumulates at the bottom of the block. Manual removal ofthe majority of the sediment at the bottom of the block is necessarybefore the alkali dip. An angled pick can be used to loosen up thesediment using the freeze-plug holes for access. The engine was nowready for a trip to the machine shop.
Although the block was chemically...
Although the block was chemically cleaned, it should still receive agood cylinder-wall cleaning. A thorough wash with soap and water willensure all the metal has been removed from the cylinder boring process.When you think the cylinders are clean, put some light engine oil on awhite rag and wipe them. If the rag has any gray color in it, thecylinder still has metal left behind.
We dropped off the cylinder heads and cylinder block for machining at GTAutomotive in Eustis, Florida. We're always inspired when we visit GTAutomotive because the owner, Glen, is usually at the engine dynotesting one of their many high-horsepower creations. On that day, thedyno was putting a big-block Chevy to the test that another employee,Mark, had assembled. There's nothing quite like the sound of an 800hpbig-block at 8,100 rpm. We're fortunate that Glen will work with us onthis mundane engine build after listening to that big-block Chevy. Markwill install the S/S intake and exhaust valves from PAW, along with avalve-seat rework on the L98 aluminum cylinder heads. The first step inthis process is cleaning the cylinder heads and checking the conditionof the valve guides. The heads will have some aluminum material removedfrom the combustion chamber bowl to enhance flow. While the die grinderis out, the cylinder-head intake ports will be opened up to gasket size.
We contacted the Crane Cams tech line for the proper camshaft andrelated valvetrain components. Mark installed the Crane Camsvalvesprings on the mildly reworked cylinder heads to complete theassembly of the cylinder heads. Both of the donor engines had over150,000 miles, so we replaced the hydraulic roller lifters with matchingCrane Cams lifters.
Install the crankshaft into...
Install the crankshaft into the main bearings dry. Apply a strip ofPlastigage to the entire crankshaft-bearing surface, then install themain cap and torque properly. Do not rotate the crankshaft during thePlastigage clearance check. Remove the cap and compare the strip ofPlastigage to the chart on the package. As the Plastigage is squeezed bythe bearings, the strip will become wider. The clearance should be inthe .001 to .0025 range for proper oil control.
Performance Automotive Warehouse supplied most of the necessary piecesto assemble the 383ci short-block, which included its 383ci crankshaftkit. We also sprung for the one-piece rear-main-seal crankshaft option.PAW supplied the S/S valves for the original '89 Corvette L98 aluminumcylinder heads. We decided on the cast crankshaft from PAW to keep costsreasonable; since rpm will be limited, the cast crank is fine.
GM made a few valvetrain changes during the '86-'91 aluminum cylinderhead run. Pushrod guideplates were used the first few years, then"pseudo" ones were used with rocker arms that had guide rails. Thepseudo guideplates will not control the pushrod properly, and thepushrods that were used with them were a softer material. If hardenedreplacement guideplates are used with the soft pushrods, they will beeaten up quickly. We decided on hardened guideplates with matchingpushrods, which allowed us to use roller rocker arms without guiderails. We don't plan to run the engine at sustained high rpm, but withthe new Crane Cams components installed, we'll have the confidence tospin the engine to its rev limit without fear. After all, you never knowwhen a trip to the dragstrip may be necessary.
While Mark was working on the cylinder heads, Glen was inspecting andmeasuring the cylinder bores for boring and honing. Cylinder bores mustbe straight and round for proper piston-ring sealing. That's not to saythat using a hone in your 1/4-inch drill wouldn't work under a shadetree. It's possible for new piston rings to seal worn cylinder bores,but it takes many miles to finally fit the ring to the bore. Glen wasready to bore the block to 4.030 inch to straighten and clean up thecylinders for optimum piston-ring sealing. First, the cylinders arerough-cut with a boring bar, then finished with a hone to provide acrosshatch pattern. This pattern helps provide oil while the rings fitthemselves to the cylinder bore. Piston-ring manufacturers havecrosshatch-pattern preferences to avoid undue break-in piston-ring wear.
The ring end gap should be...
The ring end gap should be checked and adjusted before installing therings on the pistons. Most piston rings are a little looser thanrequired so they don't require sizing, but you never know. The rule ofthumb is: .004-inch ring-gap clearance per inch of cylinder bore, whichcan vary with manufacturer. Piston ring sets that require file fittingfor all-out performance engines are available. File fitting piston ringsis tedious when done properly.
Now Glen was ready for a trial fit of the rotating pieces. Thelong-stroke crankshaft can make the connecting rods interfere with theblock at the oil-pan rails and at the bottom of the cylinder bores. No.2, 5, and 6 connecting rods also come close to the camshaft. It'sdifficult to check the clearances of the connecting rods and camshaft,but it must be done. Because the engine rotates freely during assembly,it's still not a sure sign there is enough clearance when engine rpmincreases.
Stock-type I-beam connecting rods have more clearance than theperformance H-beam-style. Anytime a stroker engine is assembled,clearances should be checked carefully while the engine is rotated atleast two full turns. At least .050 clearance of reciprocating partsshould be maintained at all points of concern. Once all the clearancesare sufficient, a through cleaning is necessary before final assembly.
Be aware that there is no parts warranty if the engine is assembledincorrectly or if dirt and debris clog the oil passages. This means thatall pieces must be checked carefully before, during. and after assembly.Once the trial fit is accomplished and the engine is ready for assembly,every component should be washed again. You get one chance to assemblethe components correctly to prevent catastrophic damage. The cleanedparts should be blown off and all oil holes blown out with compressedair, not dried with a shop cloth. Shop rags or cloths have fibers thatwill leave lint sticking to the components. It may seem insignificant,but the cumulative effect is that the fibers are washed into the oil panand are sucked into the oil-pump pickup screen. If the fiber doesn't endup in the oil filter, it will still limit the amount of oil flow to theoil pump. Good oil pressure with limited oil flow will destroy a set ofcrankshaft bearings and usually causes valvetrain noise from the limitedsupply of oil to the hydraulic lifters. Be aware of this when doing anyengine repairs that require extensive invasive repairs.
Keep a close eye on the compression...
Keep a close eye on the compression rings' gap position. If all thecompression ring gaps are lined up during assembly, excessive oil usagewill occur. It's easy to miss a ring out of position when installing thering compressor and finally the piston. We make a habit of installingthe piston rings in one particular order, which helps prevent incorrectring installation.
Main and connecting-rod bearing clearance is critical for proper oilpressure and flow. If bearing clearance is too tight, the flow of oilwill be restricted, causing the bearing to become overheated from lackof oil over its entire surface. Excessive bearing clearance will causelow oil pressure, and additional flow is necessary to keep thehydrodynamic wedge of oil between the bearing and crankshaft surfaces.Glen used micrometers to measure our crankshaft clearances, which arecostly for the home garage. At the very least, bearing clearances shouldbe checked with Plastigage.
Good-quality engine oil is fine for bearing lubrication if the enginewill be started within a week of installation. If it will be longer thana week, assembly lube should be used to keep the bearings coated.Flat-tappet camshafts must be lubed well with moly lubricants to preventcam-lobe wear, even if the engine is to be started the same day asassembly. We'll prime the oiling system right before startup to ensureadequate lube during break-in procedures.
The oil pan requires modification...
The oil pan requires modification for connecting-rod clearance (in mostsituations) when a stroker engine is assembled. The blue dye was used tolocate the clearance issue. A small ball-peen hammer can be used tomodify the pan enough for clearance. The same engine rotation ruleapplies here: rotate the engine through two full revolutions with thepan in place before final assembly.
An application of light oil should be applied to all internal boltthreads to allow proper bolt torque. The exception would becylinder-head bolts. These bolts go into open holes in the cylinderblock, requiring sealer to prevent internal coolant leaks and externalleaks at the outer cylinder-head short bolts. Teflon or Permatexaviation sealer works well sealing the bolts to the cylinder block. Thesame open bolt-hole situation applies to the intake manifold andwater-pump bolts. As a rule, Teflon sealer should be used to seal theintake bolts that go into the aluminum cylinder heads. Permatex aviationsealer works well sealing the intake bolts in cast-iron cylinder headsand the water-pump bolts.
A clean, well-lit shop area allows assembly with minimal concerns.Clearance issues and final cleaning are the toughest to overcome. PAWassembles a great 383 crankshaft kit that will work the first time withminimal assembly required. PAW has many engine options available, fromrotating assemblies to complete engines.
The Tremec five-speed transmission is on the way, and the engine will bedyno-tested before our next Shark Attack installment. We'll show you theengine and transmission install, along with the dyno results. We can'twait to give the shark a long road test. We're trying to have SharkAttack ready for the Hot Rod Power Tour, which starts June 4 inMinneapolis and ends in Kissimmee, Florida, on June 11. Hope to see youall there.
It's always a good idea to...
It's always a good idea to tack weld the pickup assembly to the oil pumpafter checking oil pickup-to-pan clearance. The pickup should be 1/4 to1/2 inch off the oil-pan bottom. Depending on the oil pump used,crankshaft clearance can be an issue, so you get to rotate the engine afew more times.
Here's our finished rotating...
Here's our finished rotating assembly ready for the finishing touches.Even with the oil pan off, it's hard to tell a 383 lurks inside. Thestock '87-'91 L98 Corvette windage tray works with slight clearancing atthe X reinforcing ribs. We were able to move it enough with a slightbend at the X to clear the connecting rods.
The new 383 engine assembled...
The new 383 engine assembled with cylinder heads that feature the new Crane rocker arms.
Chevrolet Engine Torque Specifications
Main bearing bolt (two-bolt main) 80 lb-ft
Main bearing bolt, inner (four-bolt main) 80 lb-ft
Main bearing bolt, outer (four-bolt main) 70 lb-ft
Oil pump to main cap bolt 65 lb-ft
Connecting rod nuts 45 lb-ft (Connecting-rod-nut torque varies depending on connecting-rod-bolt manufacturer)
Harmonic balancer bolt 70 lb-ft
Cast iron cylinder head bolts 65 lb-ft
Aluminum cylinder head bolts 67 lb-ft
Intake manifold 35 lb-ft
Camshaft-gear bolts 15 lb-ft