C4 Corvette L98 – to upgrade or not


As I have mentioned before, I have a 1985 L98, pretty much just like it came from the factory. It still has the exhaust manifolds, no headers. It still has what looks like the original catalytic converter. But I did replace the mufflers with muffler eliminators to give it a better sound. Easy cheap modification to your C4 Corvette for a little better rumble under acceleration.

Nothing done to the engine. Still has all the regular L98 crap on it. It does have the 4+3 manual transmission which comes with a slightly lower gear on the rear axle. This does make it slightly quicker than the same L98 engine as an automatic.

Is it super quick and fast, not really. It’s not that I do any street racing and see if it can hang with other cars, but I can tell it’s not that quick from a start and even slower if trying to pull someone from a standing speed. I always thought if someone really wanted to drag race me a 1/8 of a mile race would work best. Especially if the other car is an auto.

If you are like me you might have thought, do I upgrade my engine and if I do how?

Things to consider before attempting an engine upgrade or change

You will need to decide what type of engine change you want to make but before starting that, there are other things to consider.

First thing and most important to consider is how much money you want to spend. Coming up with a solid budget to start is a great way to go. Otherwise, you can throw money at your car until you’re broke. Having your budget and sticking to it should be the main thing to start. Also, who is doing the work? If you’re like me, you plan on doing the work yourself which helps keep the price down. If you plan on having someone else do it the cost go up quickly.

We are talking about a 30ish year old car. Once again if it’s like mine and has mostly original parts on it or if you’re not sure it’s best to assume it still does. But if you upgrade your engine to more power, because, why else do it. It will put strain on other parts of the car.

What about a new transmission to handle all the power? If you still have the original transmission on at least one that might not handle additional power you need to consider a trans mission update or change

The additional power will also affect your rear differential. Once again, original or older or you’re really not sure you’ll need to consider addressing the rear end to adjust to all that additional power.

With more power comes the need to slow down or stop that faster car. You’ll need to consider the brakes as well. If you want to go faster you’ll definitely want to be able to stop.

Will the current suspension handle this new engine or power? Will you need a new radiator to keep the more powerful engine cool? Will the fuel pump that is currently in the car work or will you need to address the fuel system.

Some of these questions might be yes, some might be no. But it is important to be aware of other possible issues a more powerful engine brings.

Upgrade your current (L98) engine?

The post addresses the L98 engine. Since C4 Corvettes also came with the LT1 and the LT4, there are different things to consider when you have one of those. They have more power and might be enough for your needs.

There are a ton of changes you can do to your L98 engine to get more power from it. Once again it depends on what you want to spend. If you look around enough one of the things that limits the L98 the most is the exhaust. Lots of literature out there about improvements there.

Most common bolt on upgrades and power increases:

  • First easy thing is to do a tune up. Make sure your car is running at it’s best. Plugs, wires and ignition module can do wonders especially on a car that hasn’t been adjusted a while.
  • An exhaust upgrade is one of the biggest improvements that can be made on a L98. From headers to straight pipes or a high flow cat and even removing the mufflers can make a difference. A lot depends on where you live and what the emissions laws on your vehicle. Be sure to check these before spending money on an upgrade.
  • Some more intensive improvements
    • Cam and intake. Lots of options here, do some research to decide how much you want to tackle here.
    • Cylinder heads, once again some options here as well.
    • If you really want to make some changes consider update your engine to a 383 stroker.

Do an engine swap?

Once again, a lot of options here. The most popular in the automotive world is to upgrade to some sort of LS engine. You can try to find one out of a later model Corvette like a C6 or find one the is a GM truck and make some upgrades to that. There is a lot to change on an engine swap. The drive train will probably need to be upgraded as well as the computer module that is the brains of the engine. Lots of info on the internet about this.

Other option, go electric? There are some companies out there that sell electric engines you can swap for a V8. Yes, I know a sensitive issue for lots of people. Not something that I would do but I just wanted to through it out there.

Maybe just enjoy it as is?

What are you really looking for in your C4 Corvette? Are your really going to take it to the “track” and drag race it or run some handling course events? Or are you just looking for something you can cruise around in from time to time and enjoy on nice days?

Lost of things to consider. If you want something reliable to drive I would suggest leaving it pretty much original. Once you start changing things you can possibly cause issues other places. This can lead to more things to fix and more money to spend. Depending on your budget these things can eat up what you have to spend real fast. Plus I see some people looking to drive their Corvette daily and if you’re constantly fixing things daily usage isin’t going to happen.


I’ve personally gone through looking at all the options and ideas on improving my C4 Corvettes performance more than once. I looked into adding more power to the engine to make my Corvette a little faster. But really, where does it end, get to 300hp, 350hp, 400hp? It can be a never ending quest.

In the end, I just decided to enjoy my 1985 Corvette as it is. No it’s not the fastest car on the road and there are mom mobiles that can beat me off the line. But in the end it’s a Corvette and something I really like to drive. It’s great to have the targa top off and rip thought the 4 speed as I head down the road. Plus it’s a kick in the pants to take on curvy mountain roads.

But the great thing is, I can always change my mind and modify it later if I decide too.

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