In the September '06 issue's article "Join the Vette Set" (pp. 95-96), the Factoids read, in part, that "1984 was the peak year for C4 production, with 51,547 built. That's a whole lot of L83 Cross-Fire cars to avoid."

What else is wrong with the C4 besides the engine (and, therefore) reason to avoid them?

I ask because I've found a cheap one with a seized engine.  Obviously, I'm ditching the seized engine, but what other problems with the car will I run into?

The C4 ranges from 84-96...not all had bad engines...actually, the only one that you want to stay away from was the 84 crossfire injection.  From what I've heard, the 4+1 manual trans was a joke...the one instance where the automatic was hands down better.  The digital dash in the early models can be difficult to see during the day time from what I hear.

If you are planning on drag racing the thing, then there will be plenty of weak points including trans and rear end (we are talking serious racing...in which case a vette may not be the best choice to begin with), but if you just want a cool car to take to the strip occasionally then they should hold up just fine.  It'll have a 700-R4 if its an auto...which will have the vette servo making shifts much better than those on a camaro or firebird...I'm sure there are other upgrades the factory did to them as well.  

You'll probably have to check your emissions laws before making too many changes...but it shouldn't be too big of a deal

Should be a fun car...great handling...plus...its a Vette!

What exactly was wrong with those cross-fire injection L83 motors, just out of curiousities sake.

Nothing makes a car lighter than a rust hole in the fender.

Mostly the computers weren't smart enough or reliable enough back then to keep em running correctly. GM had all kinds of trouble with their special engines. My Dad had a 81 Eldorado Barritz with the 8-6-4 motors where the computer would shut down cylinders while under cruising. These were sold because of the gas crisis in 82-83. Unfortunately, a sudden hit to the gas or the brake would cause the car to stall. If the car stalled in the four cylinder mode it wouldn't restart.  Computer controlled injected V8's need all cylinders to firing in order to start. I don't know how many times my Dad would pull the computer fuse in order to reset it. My Dad finally made the dealer give him a Eldo with plain 6.0 gas motor.

What's scary is GM's new trucks now have the same tech. Running on four cylinders while cruising to save gas. It's amazing what keeps showing up every time we have a new gas crisis. Hopefully, these new CPU's in these cars are up to the challenge.

I imagine those cross fire motors would be very hot running on a modern aftermarket computers like the ones F.A.S.T. makes.

I've always heard to stay away from them...not sure if the computers were stupid as the other guy said...its possible, I've just never heard it.  The biggest thing is just that they were extremely weak...and really did not respond to upgrades.  The first thing anyone does with one of those is toss the intake system (everything...throttle bodies, intake base, computer...air cleaner...you get the point).

I checked into it a bit more...first off...everything (pistons, rods, crank) is cast (not surprising...).  Heads are iron...not L98 heads (since L98 didn't exist at the time)...probably just smog heads left over from the late 70s.    

The intake is horrid...
176 CFM @ 28" Stock CFI
199 CFM @ 28" Stock TPI

So you basically don't get anything worthwhile except the block...which you can get anywhere...

The biggest problem is the intake, very restrictive, very poor mixture distribution, and poor quality control on the multiple TBI units.
The head's weren't that bad, but weren't as good as even the L98.  

the biggest deal about the crossfire engine was the air gap under the tbi units would screw with the temp reading and cause it to go into "choke" mode wich made the things run rich,you never really saw them around my part of the country,new england.i do believe arizona speed and marine deals with hop ups for these engines.i read that when set up right they could run very well.i would try and make one work just for the different factor.good luck with it.