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1979 Chevy Corvette - L98 Decision: To Build Or Not To Build

Considering our engine options for Project Shark Attack

Chris Petris Oct 19, 2005
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Our Shark Attack engine looks mighty tired. Time to do something aboutit.

We finally drove Project Shark Attack out of the shop to give it amuch-needed wash. The brake issue still isn't solved, so we weren't ableto drive on the road, but we did use the e-brake for low-speed stopping.The dilemma is: Do we just put basic stainless steel-sleeved calipers onthe car, or upgrade to the Force 10 aluminum calipers from StainlessSteel Brakes? There is a considerable difference in price, but theperformance gain is dramatic. The SSBC calipers save weight and havemore clamping force.

At this point, the cost of the engine and transmission must beconsidered before making the final brake decision. While we think aboutthe brakes, we'll remove the engine and transmission for finalengine-bay cleaning and prep. The frame and firewall will receive thesame DP90 semigloss urethane finish.

Rebuilding the original engine and adding a few performance goodiesincreases the fun factor, but a few things bug us about the earlysmall-blocks. Oil leaks are common because of the cylinder-head design(a poorly designed cylinder-head rail where the valve cover sits allowsoil to permeate the gasket) and the two-piece rear main crankshaft sealleaks at high rpm. Yes, it's possible to stop the leaks, but it takesmore work when building the earlier-design engine. Over time, thegaskets will still leak--it's just a question of when. The earlyflat-tappet camshaft versus the late-model roller camshaft is also astrong case against using the early cylinder block.

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We just happen to have an L98 engine ready for a rebuild.

The one-piece, rear-main-seal small-block with a roller camshaftprovision was available in 1987, with the exception of the '86 Corvetteconvertible, which used aluminum cylinder heads and a roller cam. The350ci truck engines didn't use roller cams in the early blocks but thetruck blocks used the same machining as the roller cam-equippedpassenger-car engines. So even if a truck short-block is used, theflat-tappet cam could be replaced with a roller cam.

Roller camshafts reduce friction and allow a more aggressive ramp on thecam lobe. Having all this knowledge makes it difficult to validateoverhauling the original Shark Attack engine. It just so happens we havean '89 L98 roller-cam, aluminum-cylinder-head engine available. It hasover 100,000 miles, but can be freshened up easily. If we use the L98engine, friction will be reduced, the cylinder heads are lighter, andoil-leak possibilities will be virtually eliminated. There are lots ofpositives to consider.

Even though we currently have an L98 engine in the shop, '87-'91 L98Corvette engines are readily available at reasonable costs. A completerunning engine with the Tuned Port pieces, including the computer andwiring harness, can be found for approximately $1,000. Short-blocks withcylinder heads are usually $600. If we don't want to keep the originalShark Attack engine, we can sell it for at least $400 (in runningcondition) to recoup a little from the L98 purchase.

The next question is, do we keep the engine at 350 cubic inches or makeit a 383? The increased cubic inches would allow lower engine speedswith a moderate cam profile, making the combination streetable. Since weplan to use the Keisler- engineered five-speed with OD, the high torqueoutput would eliminate some shifting in city driving.

In Shark Attack Part 6, we mentioned the Holley throttle-bodyfuel-injection unit for a fuel-system upgrade with a Holley dual-planeintake manifold. We'll use this for several reasons, and once afactory-style air filter is installed, the injection system will bevirtually hidden. The price is approximately half that of the portfuel-injection system. The 900-cfm Holley TBI unit will allow maximumpower and driveability from a 383ci engine. Since we don't plan to turnthe engine past 6,000 rpm, the cylinder heads won't require high-dollarporting to enhance top-end power.

Our latest research shows we can build a street/strip 383ci engineassembly for $2,551.11, including all cylinder-block and cylinder-headmachine work. To arrive at this final pricing structure, we're using alist of parts from the PAW parts book and the typical machine shop laborcharges in our area. The engine overhaul parts list is extensive, withmany custom pieces for a high-torque fuel-efficient engine. The engineidle would be slightly noticeable with good vacuum and power up to 5,500rpm. Since virtually all of the rotating engine components will bereplaced, the castings are the only pieces we'll reuse. Performanceengine builders always prefer seasoned engine blocks and cylinder heads.

The engine parts should be ordered ASAP so the new piston assemblies canbe dropped off with the cylinder block and cylinder heads for properfitting. While the parts are in transit, the L98 long-block engine canbe disassembled. The machine shop usually requires 10 days to processthe engine components, so consider this if you decide to overhaul anengine. One benefit of rebuilding the L98 engine is the engine can bebuilt and ready to install, leaving the garage a little less cluttered.

Do we build a custom '87-up L98 engine or do we consider using a GMcrate engine? The GMPP ZZ4 crate engine is the closest we can come tothe L98 custom engine, with a cost of $3,795 plus shipping. The ZZ4engine is 350 cubic inches, but is comprised of totally new components.We should come in at $3,180.16 for a blueprinted and balanced 383engine, even if we had to buy a long-block engine. If we decide to keepit at 350 inches and use the original or stock valves, we could saveapproximately $600. We would need to do more machine work on the 350components, so the savings would depend on the original condition of theoriginal parts.

The L98 engine requires disassembly and assembly, and the cost isn'tincluded in the estimate. Our local machine shop charges $500 forcomplete disassembly and assembly of the 383ci engine. There is nodiscount if you disassemble the engine and, in most cases, the cost ishigher. Engine assembly would not be much different from assembling a350ci engine except for checking rod clearance at the cylinder block andcamshaft. Using stock-style connecting rods allows more clearance thanperformance connecting rods. Of course, the additional cubic inches with400 hp and 380 lb-ft of torque would be a lot of fun on Saturday nightat the dragstrip. If we can come in at the $2,551.11 by rebuilding ourown engine, we can almost justify upgrading to the SSBC Force 10calipers.

Engine Component List

PAW crankshaft 383ci kit includes:

Probe forged pistons (your choice of compression ratio)
Moly piston rings
Set of stock connecting rods (shot-peened)
Clevite P-series connecting rod and main bearing set
Custom-ground cast-iron crankshaft (external balance)....$659.00

PAW crankshaft kit options:

Install chrome-moly connecting-rod bolts....60.00
Custom balancing of rotating assembly, including press piston pins or hone connecting rods for floating piston pins....120.00
One-piece rear main seal crankshaft additional cost....50.00

1 PAW-M155HV....Oil pump....28.95
1 PAW-155S....Oil pump pickup tube assembly....7.95
1 CRA-109821....Crane camshaft....279.95
1 CRA-99838-16....Valvespring set....97.95
1 CRA-99944-16....Valvespring retainers....53.95
1 CRA-99097-1....Valve retainer lock set (keepers)....27.95
8 SSI-10401....Stainless steel intake valves (6.50 ea)....52.00
8 SSI-10403....Stainless steel exhaust valves (6.50 ea)....52.00
1 PAW-2148HR....Hydraulic roller lifter set....124.80
1 CRA-11746-16....Crane energizer roller rocker arms....189.95
1 COM7808-16....Chrome-moly pushrods....30.95
1 MNP 42151....Pushrod guideplates....19.92
1 PAW-514....Timing chain and gearset....54.95
1 KS2664....Fel-Pro overhaul gasket set....124.95
1 PAB-0700....Head bolt kit....29.95
1 PIO-S1018....Head bolt washers....4.95
1 PIO-DA400....Stock-style harmonic balancer....79.99

Machine Shop Labor

Bore cylinder block....$96.00
Deck cylinder block....65.00
Wash cylinder block....50.00
Install cam bearings....30.00
Three-angle valve job....95.00
Surface-grind cylinder heads....30.00

Machine Shop Parts
Cam bearing set....$20.00
Brass freeze plug set....10.00



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