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.