stanklr

Hi guys,
1-Im looking to buy a used 30-50k miles 02-03 C5 Z06, I was wondering how reliable are these cars? What could possibly go wrong? Are there anything I should be looking for before buying one? Any known issues with these cars?
2-Im also looking forward to do full exhaust intake tune, how the engine and tranmission will hold these mods? They will be fine?
3-how would a full bolton c5z stand against a full bolton ls3 c6 in a straight line race (ofcourse in dragrace)?
4- what would be a better car with less issues, 07 c6 or 03 c5z?
Thanks

Dave_2003_TRZ06

They are pretty solid, but you are getting a 10+ year old car. I would definitely plan on having some money set aside for repairs. There are the usual electrical gremlins to watch out, check out the C5 Ultimate FAQ

Just find a nice car and spend a little more now, rather than later. If the car has been properly maintained you probably won't have to worry too much about big ticket items down the road.

NatB

1) Possible valve spring issues ( replace to be safe seems to be the motto)

2) Pull out the battery and battery tray and carefully inspect all the wiring and vacuum hoses ( the battery sits about HVAC vacuum control hoses and the the computer)- battery acid can cause a lot of damage, corrosion, and this is a common problem. If you buy the car, replace battery with something like a RedTop which is less likely to leak.

3) Transmission seal leaks

4) Rear axle seal leaks

Relatively minor issues- except for item # 2 which can cause a lot of problems.

ApexerER

I would say in a drag race it is going to come down to who the better driver is with a stick shift and who gets more traction. If you ever go to a track you will see that all Corvettes run wildly different times and this has a lot more to do with the driver and traction than it does with the car....

95rtturbo

2. Yes, they will be fine with those mods.
3. A full bolt on LS3 C6 should pull an equally modded LS6 C5 ZO6. However, you mentioned an 07 C6 in your post (the following question) - that is an LS2.
4. There is a better chance the 07 will be more reliable, just based on the fact it is 4 years newer. However, it will also cost more. C5 ZO6s are pretty reliable if well taken care of.

SOMFormula

I'm selling mine.
I fixed some of the issue's that plauge these cars, but it wasn't anything major or bad. And most things are just maintenance.

The '03+ have a different ABS/TC module that is cheaper to replace should it ever fail.
The brass gears for the headlights are a good upgrade.

I hang out with a bunch of F-body/Y-body owner's all the time who just BEAT on there cars. Personally, I couldn't do that to my own cars, but its nice to know that they are so reliable...even considering all the abuse I see other owners give these cars.

I am a fan of maintenance. And that's on EVERYthing. Brake fluid, clutch fluid, and PS fluid are commonly overlooked.
I put Amsoil through my vehicles. On my Vette, it is all stock except I replaced the thermostat for a cooler one and I swapped out the DexCool for Amsoil Anti-freeze/coolant + Coolant Booster and used Distilled water. I also had the guy who tunes my Firebird turn the fans on sooner. This helped a lot when its 100 degrees outside. The car never goes above 190 and the A/C is FRIGID now. I have Amsoil Syn brake fluid in the brake system as well as the clutch fluid. Amsoil Trans/Diff fluid. Amsoil PS fluid.
I don't drive it much in the winter...so never really never worried about the temps in the cold. And I'm in CA...so it doesn't get that cold here anyways.

Laser Guided

2 things that I don't think have been mentioned yet.

-Column lock. Get the bypass kit or you may be left high and dry at a bad time
-Transmission. When driven hard (like they are meant to be driven anyways), some people, including myself, blow the synchros due to some weak components used in the trans. Best fix after that happen is to call RPM transmissions

As for the valve springs, there is a big topic floating around here that has a ton of details. And someone please correct me if I'm wrong, but I think most late model z's (03/04) were pretty much good, right?

C66 Racing

I've been racing my 02 Z06 in the SCCA T1 (next year T2) class since 03 after using it as a daily driver for about two years (bought in 01). Our mods, listed here SCCA T2 Corvette, are mostly for safety, but for the past several years we were allowed to run headers, no cats, no mufflers and a very aggressive tune. Probably making about 390 at the rear wheels. No problem with the engine, tranny in race conditions with these minor mods.

For 2013, I have to put the stock manifold back on and add a 63mm restrictor to the intake due to a class reorganization.

There have been some lessons learned over the years in this area:
- Tranny rebuilt to use upgraded internals with steel forks. Vendor RKT Performance has a good page on upgrades to the T56 tranny:
http://rktperformance.com/why-upgrade/
- Raising the rpm limit has risks.
Ensure the engine has the damper in the chain v:
From the 2004 GM Performance Parts Catalog: page 106:
88958607 Timing Chain Damper, LS1, LS6
“This timing chain damper is intended for high engine speed applications and is used to improve timing chain life. Some blocks require drilling and tapping- an instruction sheet is included. “
Ensure the engine has an upgraded chain (and I think even this part number is old, but the original chain from ~01-03 has been made stronger):
GM PART # 88958608
CATEGORY: Belt or Chain, Engine Timing
DESCRIPTION: CHAIN
- If the harmonic balancer is removed, don't reuse it get a new one (the aluminum will lose the press fit and it may come off and you'll lose the oil seal behind it). Also put red locktite on the bolt that holds it in although the shop manual does not require this.

As mentioned above, a few other minor annoyances such as the left axle seal which I replace every season and the clutch throw out bearing which I have changed several times over the years. Have only done the master cylinder once. If you ever have the engine out, I'd add a clutch bleeder line - LAPD has one.

Whichever way you go, enjoy. The Vette is a pretty robust car and the C5 is very cost effective these days. Can't believe you can pick up a good low mile C5 z06 for low 20s!!!

Eric Reeves

My car is a 2002 that just hit 76k mi that I have owned since 4k mi. Only mods are headers and tune 380rwhp. Drive it daily and average 20mpg in Seattle traffic. Plus I track it at Pacific Raceways and at The Ridge in the same configuration as I drive it on the street with the exception of tire pressures. I have yet to have a single component failure but I do maintenance religiously. I have experienced no leaks including the rear. The eye opening experience (and I suggest you look for) is for a replaced windshield. If not done correctly you will experience LEAKS at the A-pillars that you will chase forever. It can be because of A) Improper sealing of windshield against the frame b) Improper sealing of the reveal molding C) Improper sealing of the track up and around the windows D) Need to replace weatherstrip or in my case E) All the above because the shop I used did not know ANYTHING about how to do so and they came recommended to me from a Corvette guy. You can find out if your prospective car has this issue by taking a water hose to it and don't be shy. Water will be in the floor if you have issues. Took me a long time to find it ALL but I do love this car. Will not let it go until I pass it on to one of the kids. Good luck.