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C5 & C6 Corvette: Necessary mods for on track reliability

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  • C5 & C6 Corvette: Necessary mods for on track reliability

    This is a quick little tech article we wrote in answer to a customer's question:

    ...what are the NECESSARY mods to make a C5/C5 Z06 reliable/durable on track. Performance aside, what needs to be done component wise to make one reliable lap after lap

    That is a great question and one I feel we can answer. Because they are so similar we have lumped in the LS2/LS3 powered C6 Corvettes into this same post. We mined our own build thread for images and upgrades, plus had input from Anthony at HorsePower Research, who has been around track prepped Corvettes for twenty years.


    Before you ask, no - Vorshlag is not a "Corvette Shop", but after 17 years in business building race cars and 34 years of on track experience, I can answer this question with some small level of authority. I have also owned 5 different Corvettes (C4, C6) and have a bit of experience in several C5/C6/C7 track cars.

    Here are the reliability mods we have utilized, track tested, and recommend - without getting into the "go faster" bits.


    Number one with a bullet - cooling. The plastic/aluminum radiator that comes in these cars is pretty inadequate for even a moderately talented driver, especially in hotter than average ambient temps.

    We recommend a DeWitts (or similar) larger capacity all aluminum radiator upgrade plus a 180F thermostat upgrade for any C5/C5Z06 that is going to see more than 1 track day per year. The size difference alone should tell you something!

    And clean the junk that gets jammed up in the condenser and radiator area, too! Don't be surprised if the radiator core is bent - it happens. The age of these cars now also makes the original water pump, hoses, and belt also suspect. Check everything and don't skimp on the little things like clamps, too.

    The DeWitt is massive but it fits inside both the C5 and C6 radiator shrouds. While you are down there, look at the power steering cooler and straighten the fins on that, too. If it even has fins... that's a whole other upgrade (power steering cooler) but you can read more about that here.

    Since it is a part of the pressurized cooling system, the factory remote coolant reservoir and radiator cap should be replaced as well. I had bought one for my truck at the same time, so that's the second one in the picture above left.

    The lower radiator support on all C5 and C6 models is a fabricated aluminum structure - and it is the lowest thing on the car. With an aggressively over-lowered front ride height, it is common to see this lower support smashed to bits and held in by the surrounding plastics. Luckily the aftermarket factory replacements are inexpensive.

    The replacement is often raw aluminum, and you likely don't need to bother painting it. As we have seen before these low cost replacements tend to fit well and include all of the factory installed riv-nuts to attach all of the lower bits and pieces.

    Want to log your temp / pressure data on something like an AiM SOLO lap timer? Good luck! These 1997-2004 C5 cars have some very rudimentary OBD schemes and AiM has no firmware for the CAN interface. Being a post 1996 model car there IS limited CAN data, just might need some trickery to get it into a modern data logger.

    At least a C6 has a supported CAN model by AiM and we often log about 15 GM channels over CAN in our 2006 C6 - just know that the oil pressure is in Metric while the rest of the data is in SAE. The factory "digital gauge" on the C5 and even C6 are both pretty limited, and can only show one temp / pressure at a time. The little analog gauges are a bit better and can be checked at a glance, but they are all driven by $10 sensors. A decent set of gauges with new sensors isn't a bad idea. But probably not necessary unless you have added a good bit of power.


    Like virtually any factory built car this side of a Porsche GT3, the original equipment brake pads, brake fluid, and brake flex lines are always suspect for track use. And being 20 years old, there is NO TELLING what rando parts store brake pads you have in your C5. Just assume they are junk and add a real track pad + quality fluid + some stainless braided Teflon brake flex lines for the ultimate in reliability.

    While you are swapping out the pads check the rotors for excessive cracking (the above left 2-piece rotor was well beyond its useful life) and peek at the piston dust seals on the 2-piston front brakes. The C5/Z06 and base C6/Z51used these same PBR 2-piston sliding calipers (from around 1984) up front and a 1 piston slider in the rear. These are cheap to replace with fresh rebuilt units - if they look like this, replace them.

    If the pad thickness is the same or less than the backing plate, they are done. And get a good brand of track pad to go in at all 4 corners. I'm not going to preach one brand of brake pad is better than all the rest - that's just snake oil sales tactics. Instead, most brands make track rated pads that can work. Like almost everything, "you get what you pay for" - the cheaper brand track pad options don't last as long as the costlier options from "better brands".

    Avoid the ultra low end brands like EBC or Powerstop and get a "track rated" pad from your favorite brake pad supplier in the brands you prefer: GLOC, Carbotech, Hawk, Pagid, PFC, Project Mu, Porterfield. Don't know what to get? CALL A SHOP that sells these brands and has experience with track events!

    Brake fluid - stick with DOT4 racing brake fluid options from big names like Motul (RBF600/RBF660), Castrol (SRF), Hawk or even Wilwood. Stainless braided flex lines - stick with Goodridge, Stoptech or similar.

    Of course if you call us here at Vorshlag and we can converse intelligently about G-LOC brand pads. The typical C5 track enthusiast would be well suited to an R12 front / R8 rear pad compound, but depending on your experience, speed, tires and end uses we might go higher or lower on the track pad range for this brand.

    Lastly - don't fall into the trap of thinking you HAVE to do a Big Brake Kit. Most casual track day folks will be fine with basic C5 or C6 brakes. There are some OEM upgrade paths that cost 1/10th as much that might work for your end uses. For your first events - pads, fluid, and flex lines. But yes, lots of places you can spend money if you want to go faster.


    Again, The C5 is getting a bit long in the tooth now, so any factory suspension bushing is going to be suspect when it is 2 decades old. But the control arm bushings on the C5 and C6 were not very "track rated" even when new, especially with the modern batch of "200 Tread Wear" tires that we have now - which can produce lateral loads exceeding 1.3g.

    Even with only 1.15g lateral / braking Gs on 275mm RS4 Hankooks we popped a bushing out of the arm on our little C6. It is a very distinct sound and I knew what happened as soon as it happened on track. Braking loads are what tends to push these bushings out of the control arms, but "luckily" the factory calipers / rotors / ABS limit braking on these cars to less than other modern cars. If you start upping the ante with grippier tires, an ABS swap to a more modern system, and better suspension (coilovers) expect to have the stock rubber bushings "pop out" and clunk and bang and throw your alignment out.

    What's the solution? Well that is a rabbit hole you can fall into. For a dual purpose street / track car, I would go straight to polyurethane bushings and add them to the stock arms with grease zerks for annual grease injections (you can read more about that install here). This will keep them quiet and bind-free for years and years.

    For more dedicate track cars, replacing the stock rubber bushings with Delrin or spherical bearings is another option. Just know these will make a LOT more noise and require semi-annual replacement. Metal bushings near ground level getting sprayed with rain and grit WILL wear out pretty quickly. For dual purpose cars I've seen them go out in less than 18 months. You were warned.


    The outer tie rod ends tend to fail at a higher than normal rate, mostly because the boots that cover the grease is right next to a brake rotor at both ends of the car.

    You check for play much like you do the wheel hubs. With the car in the air but tires and wheels still mounted, grab the tire at the front and back edges and rock it back and forth. If there is any movement or play, most likely the outer tie rod is bad. Again, usually a bad outer tie rod is coupled with a cooked tie rod boot. We have made these little stainless steel heat shields that go between the tie rod end and the rotor, with an air gap.

    Replacements are inexpensive and relatively easy to change for DIYers. Whichever end you change will need a new toe alignment after. And ball joints can wear, too - those are serviceable in the existing arms, thankfully.


    This is another common Corvette wear item you need to get ahead of for maximum reliability. The front and rear hubs wear due to heat and loading, and the hotter the brakes get and higher the grip loads the faster these wear. To check for wear have the car in the air and rock the top and bottom of the tire. Any movement = a bad hub.

    Most replacement brands are complete junk - this is a uniquely Corvette phenomenon. We have used 5 or 6 brands but there is exactly one that lasts: SKF X-tracker. There are unique front and rear units, but rear units can be used at both ends.

    There are also "passive" and "active" wheel speed sensor units, so get the type that matches what you have. C5 is all black or grey wire passive. Starting in 2009 the C6 GS/Z06/ZR1 got an "active" yellow wire unit. The rear hubs can be 31 or 33 spline on the C6 as well. Lots to check! But again, there's one brand to chose from: SKF X-tracker. Any other option will wear out faster, often in one track day - that's not a joke.

    Wheel studs and lug nuts are a wear item, and if you are changing wheel hubs it is a GREAT time to upgrade to ARP 3" long wheel studs at both ends. Yes they are much longer than stock, but that one time you need to use wheel spacers, this will save you a ton of hassle.


    The first thing many C5 or C6 Corvette owners do when they buy their car is lower the ride height using the stock adjusters on the transverse leaf springs at both ends. You can lower a good bit on the stock hardware and for under $50 you can get replacement bolts to lower the height even more.

    This is something you should check as soon as you buy a used C5 - because 50% or more of these have been lowered. "Neat" for the car show crowd but beware - it has seriously major consequences.

    This is a common mistake - and one I made myself with a C5 development car! I drove the car above at an Optima event in 2015 and the rear had less than 3/4" of "bump travel". The bumpy infield road course at TMS eats up all of that and more, and when you bottom the rear shock on an over-lowered C5, prepare to take a ride! The spring rate goes infinite...

    The stock shocks (and OEM replacements like Konis) are pretty long and work only with the stock ride heights. When you lower the height you need SHORTER DAMPERS made for your new height. This is not what most folks think about, but as a suspension designer we know this all too well. Most aftermarket coilover dampers are shortened 1" to up to 2", to allow for a lower ride height within the same envelope as the stock shock's upper and lower mounts.

    Remember - you don't lower these cars unless and until you go to proper coilovers! Now of course we can help with that, and have sold many many sets of properly shortened MCS damper sets for C5/C6 Corvettes. We know spring rates, we make our own upper shock mounts for both ends, and more. But this isn't a "reliability" thing, just the only proper way to lower a Corvette plus add real spring rate.


    Again, the factory gauges for oil pressure and temp are all fed with $10 sensors that are already suspect, but that data is better than no data. Using "good oil" is a damn good idea, but pretty much any full synthetic oil will work. Again, ask on any forum or FB group and you will get 1000 different brand loyalest answers.

    This particular mix from Motul only comes in this weight, but for the hot and cold weather we see in Texas it works well - and I have used this exact oil on multiple cars and engine platforms. As for the filter, the Wix XP will do just fine.

    Mobil1, Castrol, Redline, Motul, LiquiMoly, even the pyramid scheme brands (Amsoil) will work if it is synthetic! Then pick an oil weight appropriate for track use + the coldest temps you might see. For the "cold" number start with 5W or 10W. For the high number, let's push to 40 or 50. Here in Texas we use a 5W50 Motul Ester synthetic and it works very well for all manner of engines we have abused on track the last decade, but insert your favorite brand and local temp range into that. 5W30 to 10W40 are multi-viscosity weights that can work well in cold climates.

    In November of 2022 I took this C5 to a track event on a somewhat cooler day (65F ambient) and oil temps got up to 262F on the factory gauge with 5W50 Motul. That's not terrible - but was with a massive DeWitt radiator and a cam and header 5.7L that made 425 whp. A higher ambient temp or higher power levels would push that into the 280-300F range, which is getting into the Danger Zone.

    An oil cooler is a good idea once you start to see oil temps of 280F or higher on track (which we saw in our LS2 powered C6 in summer events). Not something you'd likely need in every C5 or LS2/LS3 C6 unless you have more than stock power levels and/or track in high ambient temp areas (100F Texas summers can be brutal with oil temps)

    continued below
    Last edited by Fair!; 11-15-2022, 04:20 PM.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

  • #2
    continued from above

    When driving the C5 with the 5.7L LS1 on track last month I also noted a "low oil pressure" light once in heavy braking, and that is with only 1.24g stops, so that is a concern. Once you start seeing low oil pressure warnings it is time to invest in an oil pressure accumulator. This is a good idea for any wet sump oiling system LS powered car once you start pushing more than 1.0g lateral or 1.0g braking on track. And with today's tires that is relatively easy...

    The most common option is Canton's "Accusump" units, which come in 2 and 3 quart (shown) sizes. These are setup to trigger at a preset low pressure number, like 15 or 20 psi, so if you slosh oil away from the oil pump pickup tube briefly, the accumulator pressurizes the engine briefly. These can be pretty massive and a challenge to mount under the hood of a C5 - but it can be done.

    Another option is the Master Lube unit shown here. It mounts in a smaller package (it has a higher piston / pressure ratio to it is more compact) and would work well in the stock battery location under the hood (you'd need to relocate that to the trunk area, of course).


    This isn't a huge concern, but on an older C5 it might be time to take a look. These OEM drivetrain mounts are rubber and are now very old, if original. Check these and if you are smart, do a preventative maintenance and replace them all with OEM quality units.

    Adding SOLID mounts to all of these will DECREASE reliability, but just know that lots of people do this as they progress their C5 along the modification path. Be ready for major increases in NVH (Noise, Vibration, Harshness) and potential for breakage.


    This might seem like a stretch, but when it comes to reliability with 20+ year old Corvettes, well you are could get pulled in on the hook some day. And without any track worthy tow hooks you are going to get some damage if a flat bed has to haul your car. We make bolt-on front and rear tow hooks for the steel framed C6 and all C5 Corvettes.

    We make these from beefy steel plate that we CNC cut and bend up in-house. These are made to bolt to major structures on both the C5 and C6 chassis.

    Both our C5 and C6 front tow hook designs mount between the lower radiator support and the frame rail. Our C6 design also has a "tab" that is bent up and "pushes" on the back of the bumper beam when the car is towed forward from this point. The tow hook has a bend down, then then passes through an unused section of the lower grill - which we add a slot to some plastic (see above right) for the pass through.

    I have personally pulled both this C5 and C6 into and out of our trailer a dozens times with these front hooks - I'd confidently have a tow truck driver pull it up onto a flat bed from here. It is VERY substantial.

    Our rear tow hooks mount to the frame on both the C5 and C6, and also has a 2.0" diameter hole and is made from 3/16" plate steel. These are the strongest bolt-on tow hooks on the market.

    Lastly, if you tow your C5 or C6, strapping the rear down is a lot easier with these tie-down anchors. These 3/16" CNC cut plate steel parts can be bolted onto the rear lower control arm / sway bar point at the rear subframe on both cars.


    The torque tube is the tubular device that attaches the bellhousing behind the engine to the transaxle in the back of the car. And there are some rubber bushings that attach the inner driveshaft that will have some wear and tear.

    Another thing that is often "upgraded" with poly or solid parts that tends to DECREASE reliability, but is another common thing...


    This is a super common upgrade because LS engines (like most engines) like to spew engine oil when used on track at high RPMs. There are two common methods to add a catch can: an emissions legal "sealed" system that is plumbed inline with the PCV system, and a vented system.

    I have a good write-up on a sealed "legal" system on my C6, which you can see if you click here. It is more work and there is still a chance to get some oil vapor into the air cleaner and then the engine. You have to plumb this properly and drain it after every track day.

    A vented system also needs to be drained, but it is simpler to add. Just plumb a line from the crank case (usually from a valve cover) into a vented oil catch can, and done. This allows some minuscule amount of fuel vapor out into the atmosphere so it isn't 50 state emissions legal. And it might not be class legal in some series, like the SCCA Tuner class we ran our C6 in.


    The stock shifter is a wear item and isn't exactly a great unit to begin with. Ask me about missing shifts on track in my C6 (which uses the same shifter) - it sucks! I fought the 2-3 upshift for several Time Trial events before breaking down and installing an MGW shifter.

    With the transmission so far behind the driver, the shift rod that controls the shifting is very long - so any slop in the stock shifter is going to be exaggerated over that long distance.

    Now I'm not one to blindly buy and install aftermarket shifters on EVERY single car I drive on track, and it is more rare for me to do this. But after so much trouble with my own C6, it was time. Wow, what a difference. Have not missed a shift since, and that is good for the synchros and more. Again, check your class rules, and if you aren't missing that pesky 2-3 upshift, then don't sweat it.


    This system was used by from the mid 1990s on for their 6-speed Tremec manual transmissions, which allowed the computer to force you from 1st gear to 4th gear on a low throttle upshift. Instead of grabbing 2nd gear you ended up in 4th, and it SUCKS. These "skip shift delete" kits were all the rage back in the day and I bought this a year ago, then finally found it and had Doug install it in this round of work.

    Many C5 and C6 Corvettes likely already have this bypass device added, which will allow you to shift into whatever gear you want. If not it is doubtful would ever have this condition (warmed up engine, low rpm / low throttle upshift from 1st) happen on track. But it is still super frustrating when it does happen on the street, and you will curse this until you do the $20 bypass trick.


    That's all of the "bare minimum" reliability mods. There are several things people often like to do to Corvettes, such as:
    • Replace the awful OEM seats
    • Add racing harnesses
    • Add wider wheels and tires
    • Install proper coilover suspensions
    • Upgrade to larger fixed caliper braking systems
    • Change out the GM ABS system (its not great)
    • Add horsepower

    And the list goes on. But that's not about adding reliability, that's about making the car safer or faster, and we will save that for another post!

    Thanks for reading.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev