Sure. L98 was introduced in 85. Lore has it that the L98 TPI setup was developed for use in passenger trucks. Dunno if that's true, but they sure make teh torques. All 85 and most 86 L98s were flat-tappet hydraulic cam engines. These mills are easily identified by their perimeter bolt arrangement on the rocker covers. The late-86 introduction of a hydraulic roller cam (look for center-bolt rocker covers) freed up some hp and improved fuel economy. How much varies by model year and equipment, but here are the general numbers: 1985/230hp, 1986 230-235 hp, 1987/240hp, 1988-91/240-245hp.
You probably know the L98 runs out of breath at relatively low rpm. Plan to shift at 4500 max on the stock setup. Torque is abundant. The best track or autox strategy for the L98 is to drive it as a momentum car. Also consider adding a harness bar and harnesses. The factory sport seats are very good (base seats are meh at best) but a harness will keep you planted and able to fully exploit all the grip the chassis can summon, which can be a bunch. Harness bars are removable, which is handy, but some designs permit the bar to rotate, not a good thing for safety. The easy button for 6-point belts is the Brey-Krause anchor kit for your forward belts. If you prefer, Autopower, AS&M and others offer bolt-in or weld-in rear "cages". These have the additional advantage of stiffening the chassis. [Fun fact: the C4 was originally designed as a t-top car. The chassis engineers hit their stiffness goal, even with the tops removed. At a very late stage of development, then-Chevy honcho Lloyd Reuss decreed a fully-removable top. Although additional structure was added to the firewall area (look around the master cylinder and hood latch areas, for example) the targa top sacrificed a ton of stiffness, to infamous effect. Not particularly stiff even with the top in, a C4 with the top removed is only one order of magnitude improved over a proverbial wet noodle. Luckily, it nonetheless handles great, but keep the top in place when you race.]
ABS was introduced as standard equipment for all 1986 Corvettes. For this reason alone a 86 is preferable to an 85, other things being equal.
An important change for 88 was front suspension geometry changed to zero scrub radius. While 16" wheels were technically still standard on base-suspension 88s, relatively few were built. All 88 Z51 and Z52 cars got 17s, and 17s became standard for all cars in 89. The 84-87 suspension shouldn't be entirely disregarded, as it has some theoretical advantages in autocross, but it's important to consider that performance tires for the 16' wheels are extinct and later 17s aren't a direct-fit upgrade because of offset changes: put later 17s on and they tuck under the car, requiring either the use of spacers or very specific wheels that are not common any longer.
Because of these changes and various other upgrades, conventional wisdom is the best L98 buy is any non-base suspension, 88 or newer car. However, manual transmission options shouldn't be overlooked when deciding between an 88 or an 89-91. The 84-88 Doug Nash 4+3 transmission was a Borg-Warner Super T-10 with an electric OD added. OD is available in 2nd, 3rd and 4th gears. This transmission has a terrible rep, and the most fair accounting of it is probably to say the verdict is mixed. The T-10 portion is what you'd expect in terms of reliability; it's very stout. Throws are long but can be shortened with an inexpensive kit, though effort is raised a little. The OD unit needs fluid and filter changes the same as an automatic. For cars with lots of engine it is vital to disengage the OD before you mat the pedal. You can also reduce driveline shock and promote longevity by clutching OD engagements and disengagements.
The problem remains that the OD was added as a CAFE measure and even with it de-selected the car wants to drop into OD for you of its own accord. At one time there was a racer who did a mod to make the OD exclusively driver-controlled and I knew a few NCCC guys back in the day who did it and ran their cars hard with no subsequent problems, but I no longer know whether he is active or if the mod procedure was ever made available to the public at large. Back in the day, an OD rebuild or replacement was very expensive and contributed to the transmission's bad rep, but the good news is twofold. First, the trans works fine without OD, other than the rev penalty. You wouldn't want to drive far on the highway without it, but around town or for track use you wouldn't miss it. Second, there is a rebuild kit for the OD unit, so if you like a project you can fix your own for a few hundred bucks. Failing all else, Eckler's and probably the other big Corvette part+accessory houses will sell you a rebuilt unit on an exchange basis.
The ZF-sourced 6-speed manual trans arrived in 1989. Physically, it's bigger than the 4+3 and is not a drop-in replacement. At a minimum, the tunnel has to be cut and the shifter cutout moved, I think the driveshaft has to be swapped, plus there are probably other snags I don't recall at the moment. The ZF comes in two flavors: a "black tag" unit from 89-93 and a "blue-tag" unit from 94-96. The earlier trans has straight-cut gears and is reputed to be stronger. The downside is gear noise, most noticeably in the lower gears. If you are new to the experience, don't worry the trans is on its way out based only on the sounds it makes. In a stock-exhaust car, with the windows up and radio off, gear whine is the loudest noise in the car in first and second. The early trans is also distinguished by the reverse-gear collar that must be raised to select reverse. The blue-tag trans has a high-detent reverse gear selector and helical-cut gears. It is much more quiet. Both generations will handle hp upgrades under the hood reliably with one caveat - this trans does not like to be rushed. Leave power-shifting off the table with this one. Most owners will never have trouble but take heart if you do: the ZF Doc can repair or upgrade (But have money, these complex units require special tools to work on. Anyone who services them is gonna get paid).
The stock ZF6 flywheel is a dual-mass unit. Conventional wisdom is they cannot be resurfaced. I don't know whether that's true, but unless the flywheel has been really abused, you might consider scuffing the surface with a Scotchbrite pad and re-using an otherwise good one when you do a clutch job. Probably someone will caution this isn't a good idea since the dual-mass spring setup fatigues with age and will inevitably fail or something along those lines. All I can say is I haven't seen a failure on a street/autox car. If they are still available, an OEM replacement is expensive. Many guys swap a one-piece aluminum flywheel (think Fidanza). A steel flywheel can be adapted if you are really motivated. The lower inertia and rotational mass of an aluminum flywheel is appealing to lots of owners, but I personally avoid it because of the accompanying increase in gear rattle. At idle it can sound really awful.
Power upgrades: the L98 has super long intake runners - effectively several feet. If you like torque and want to keep the setup, be aware that the usual hod-rod tricks can actually hurt performance unless approached comprehensively. Switching to siamesed or oversize upper runners or porting the cylinder heads can reduce velocity and cost power, torque or both. A header install as a stand-alone change also doesn't really give you much. There are many resources available if you want to explore changes to the long-runner intake. Back in the day, TPIS sold miniram and superram intakes that were well regarded, but not cheap. The miniram is something you can clone on the cheap by using a later LT1 intake and drilling it to accept a distributor. This setup can be economical and make good power when done properly. The factory bottom end uses four-bolt mains but is not forged, so while there is a practical limit on the power you can extract from top-end enhancements you have to want to make a lot of power to call for a crank/rod/piston swap.
, would be outclassed at the higher levels. Our home track is Mid Ohio and it was blast there. Maybe this year...
