C4 Corvette DIY?

I had an '84 which made it all the way after my nasty 1986 divorce to 1996 (and nearly 200K miles) when I got a silver collectors edition. Like any car, there are easy jobs and harder jobs. I replaced the radiator myself once and that whole LCD dash panel twice (sent it out to be rebuilt). Starter motor twice, the flip-up headlight gears once, usual battery changes, and so on.

One great thing about the C4 is that big clamshell hood - practically no other car since the XKE Jag has had such easy engine access.

 

I have had an 86' corvette for almost 5 years now. It is my daily driver. As one would expect of a 20+ year old car from GM made during the 1980's it has given me the "opportunity" to become a better mechanic on a regular basis. There are not a whole lot of areas of the car I have not touched. I try to do as much work as I can because if you take a 20+ year old car to a regular mechanic or even the dealer, they don't know them anymore, and you are simply paying the standard hourly rate for them to expiriment. I will say that the car has never left me stranded, but I do understand that on an old car, you have to pay attention to noises, smells, etc .

As mentioned, some things are very easy, other things can be quite frustrating. The C4 vette, in my opinion, is a very clear example of GM adopting the old small block casting to new technology (fuel injection, ABS, etc). It shows, because you can really see where the engineers were told to "Make this new system work on the old engine design". That said, I have been able to do a lot of things to the car (headers, intake manifold swap, fuel injector replacement, seat and carpet replacement, as well as your standard stuff like water pumps, master cylingers, etc) myself, and when I bought the car, changing an alternator was about as technical as I got.

The internet, and corvetteforum.com in particular, is an incredible resouce for the cars. The memebers there are very hands on and can answer almost any question. I made photo-docs of a number of my projects and you can check them out here if you want to get an idea of what is involved in working on a C4:

http://members.cox.net/effergyvette/#86_Vette_Projects:

Parts are reasonably cheap, but I have had to expand my tool collection significantly to work on the car (Torx bits, crows feet..that sort of thing). The nice thing about the vettes is that almost any part for the car is available in a catalog and one phone call will have it at your door in a couple of days.

HTH!

 

The 85-91 vettes use a motor called the L98. The L98 is an odd motor for a sports car. It is basically a really good tow truck motor. The intake manifold runners are very long (over 20 inches) and this gives the car a very large amount of low end torque for a 5.7 liter engine. The trade off is the motor cannot breath well above 4500RPM, and is massively out of breath by 5500RPM. The lack of RPM is why the horsepower is so low, but looking at the horsepower numbers alone dosen't show you the massive torque the motor is making at low RPM. You can check out my dyno graphs and see that while my car makes only 230HP at the wheels it is also making 327 Ft/Lbs at the wheels. What this translates to on the street is this huge "slam" off the line, but the faster you go, the slower the car is. It is very good for stop light to stop light entertainment(responsible entertainment - of course). GM also setup the gearing so if you got to WOT around 55MPH the automatic will drop to second gear and the jump to 75MPH is quite surprising. After 75MPH the car's rate of acceleration falls off again.

I have my 99' 6 speed vette for comparison, and off the line the 86' will win easily. From 40MPH and above the 99' will simply walk away from the 86'. Compared to "normal cars" (I have access to a 2005 Mazda Tribute, a 2001 BMW 325, lincoln Town car) the 86 is much stronger with massive amounts of torque. My normal advice for someone who drives my 86' for the first time and isn't familiar with sports cars is:

- do not go to WOT unless the car is pointed straight
- do not go to WOT on warm dry roads below 15MPH
- do not go to WOT on wet/very cold roads below 35MPH


The 92-96 vettes use a motor called the LT-1 which uses much shorter intake runners and gives up some low RPM torque but gains high RPM efficiency, thus it makes 50HP more than the L98. If you prefer high RPM, then you want an LT(x) motor (GM made an LT1, LT4 and LT5 in the C4, but that is another discussion).

While we are talking about driving feel, please remember that all C4's use the half shaft as a suspension control arm and thus a lot more tire/suspension movement is carried straight into the cabin. The newer cars ride better than the older cars, but all of them ride rough. The eariler cars have many little squeaks and rattles on rough roads. The noises can be "cured" with the right exhaust system.

I bought my 99' first, so I wanted the L98 because it would not have the same feel as the LS1 in the 99'.

 

How much money do you want to spend? You can get an early 375HP ZR-1 driver now in the low 20s if you look around.

However, parts cost and complexity will be a lot more than with an LT1. Many think it is worth it - these even had good torque at low RPM thanks to a low-speed induction system and a dual pattern cam on the two intake valves. They make about the same power as an L98 with the power key turned off (disables the highspeed induction system with it's extra injectors and valves).

I will offer one word of warning (and maybe I was just unlucky) - but in 1996 for the last of the C4 cars, they had the LT4 engine with manual gearboxes only. It had 330hp rather than the LT1 at 300.

Mine spun the front main bearing at about 21,000 miles - they put in a new short block under warranty. The new block spun the front main bearing again at about 28,000 miles. There was no obvious reason for either blowup - some of the guys on my ZR-1 site claim that the LT4 had a problem with the crankshaft shifting for and aft in it's bearings which can cause this.

I can't confirm, but I bought a 2004 Z06 after it tore out the bearing for the second time.

 

Hi,

I have a 1996 C4 Corvette and really like the car a lot. It is the Collector's Edition with LT1 motor - automatic. To me, and mind you I am not a track expert or a mechanic - the car feels and drives great. Thank god, I did not have the opportunity to learn how to work on it except for very minor things (its been a solid car). Well, don;t know - I guess I just wanted to chime in.

In my opinion, performance thing aside, look wise the later 90's models of the C4 line are some of the best looking Vettes out there. Just right, not too bulky, not timid - very nice, flowing lines. A nice change from the looks of cars that are made today.

Best of luck,
Mike.

 

I've had an 84 & an 85 . Buy the newest one you can afford . They are very easy to work on compared to other cars because of the "clamshell" designed hood. If you can get an LT1 , go for it . The L98 (85-91) had alot of low end grunt , but once in the 120mph range , it kinda fell flat on its face.

 

I had a 89 6 speed. I had about the worst luck with that car. I drove it about 7k miles in 5 years and babied the car. I had constant problems with the intake leaking oil on the back. The dealer never could fix it. The climate control went out. The flywheel is what they call a dual mass flywheel. It's made of 2 pieces & cost a little over $800 for that part alone. It started making a noise that sounded like a throw out bearing going bad. I had the clutch replaced also when that was done. A coolant sensor went out. You will learn to read trouble codes. The engine is completely out of breath at 4600 rpm. I don't think I ever got it to rev past that. The fuel injectors went out ( I got to see it on a wrecker twice). The ecm went out. The rear pinion seal started pouring. The ac compressor went. The union boys in Bowling Green cross threaded the ac dryer, which made that replacement a challenging one.
There was more, luckily I don't have the receipts to refresh my memory. I wanted one so bad in college, that I put up with it. It was fun to drive, and pretty quick. Mine didn't rattle much if any. You could work on one if you wanted to with the internet as help.

 

I spun an '86 automatic by goosing it and pulling out onto a deserted road while turning right. It kicked down to first and just immolated the tires. My navigator blurted out "nothin' but rudders" as we spun because it snapped around so fast I was at full lock and it was still rotating. That was a fun car even with the automatic because of the explosive torque. The quirky ergos had their own charm as well. As mentioned before, that clamshell hood lets you get at almost everything. Buy the newest, nicest one you can afford as improvements continued through the years. I had an LT1 Camaro and maintenance on it was awful compared to an LT1 Corvette.

Neat cars, good handling, plenty of fun if you get a good one.

gp