I recently purchased a 1990 corvette with a l98 engine and 6 speed manual transmission. Engine is locked up and wanting to repower with what makes the best sense for more power. any ideas would be appreciated

 

IMO the simplest solution would be to put another L98 in place of the seized one. Move all the sensors etc from the old to the replacement and drive it.

 

Hello there,

I agree with the above post where the suggestion was to get another L98 and swap it out. This would be the simplest and cheapest way to keep the car on the road. It would also keep the car like it was "designed" to be.

Being the way I am I would probably tear your old motor down to figure out what happened and use that block again if possible for a rebuild. This would keep the numbers matching. For some reason this is sooooo important to the purists who have C3's. I expect it will be in time with the C4's.

There are lots of folks changing over to LS engines but that requires a lot of changes to the original design. We have outdated Fuel systems, ignition systems and intake air control systems but they work as a unit together. Some even like the way they work together, like me.

Keep your Corvette as original as possible and it might be worth more down the road a few years!

I hope that you can revive your Corvette and be able to enjoy it's old weirdness' with a smile on your face and money in your pocket!

 

BTW, welcome ot the forum. Now, fill in your profile and shop for a FSM if you intend to wrench on it. :-)

 

Numbers matching is great if you have a low milage everything original never going to drive it to keep the miles down car. You have a blank slate. Drop in a crate motor of whatever HP you always dreamed about and drive it like a sports car. Worry less about getting your money back someday and more about getting your moneys worth today. That's what I did 12 years ago and I still feel like a kid on Christmas morning every time I back it out of the garage. Have fun!

 

The old engine has to come out anyway so why not tear it down to see what happened to it. It may be that the block is OK so thjat cold be the starting point for a rebuild.

But you really need to have a plan for what you want in terms of power. This old saying appeared in many speed shops years ago: "Speed costs money. How fast do you want to go??" You need to have a budget. Parts can be expensive depending on the power you want. What about doing the work? How much can you do and what will have to be farmed out to a shop?

It would be much easier to get a crate motor that you can simply add the engine accessories and drop it in. That saves time and possibly some money. You can find complete engines, long blocks, short blocks that can provide lots of power.

But you also need to budget for other parts and accessories such as coolant hoses, plugs and wires, maybe a radiator, clutch assembly, and all sorts of other things. Are the brakes in good shape? Tires OK? suspension components? Do you want to upgrade the exhaust with headers, duals and performance mufflers?

 

You didn't mention how many miles are on the car but you also need to think about other driveline components. Since the engine is locked I have to assume you did not buy it before the purchase. Did the PO lock the engine through abuse or just lack of maintenance is a big consideration. If due to pushing it really hard you may have u-joint, transmission, rear end, and/or brake problems. You may want to diagnose any issues with those components prior to repowering the car since you may a lot more cost in getting it back to driving condition than just an engine.

 

If a guy wanted a 383 stroker kit installed this would be a good opportunity...

 

Here's my way of organizing your options. First option: keep the car stock or near-stock. That is an easy option and if you are more into collectibles, this is the only option. Rebuild the original L98 long block. You could change intake manifolds and add long-tube headers to gain a little power and more rpm capabilities, and these can easily be swapped back to stock if you want to do that in the future. And this is the cheapest answer, by a big margin.

Option 2: make the car faster with a drop-in gen-1 small-block. This lets you keep the ZF6 trans and ECM, albeit you will of course need to tune the ECM to address the major changes you will implement. Build or buy a 383 or 396, get some good aftermarket heads (AFR 195 competition heads or thereabouts), a well-considered cam, a short-runner intake, and go have lots of fun. I have an LT4 car but it was essentially built this way, and it is really fun. There is no fabrication or adaptation required for this upgrade, and your drivetrain is fully up to the task. This is the mid-priced option, and there is a ton of info out there on it.

Option 3: move to LS power. This is popular for a reason, and IMO the C4 chassis is begging for this conversion! But it will require either a T56 transmission or some adaptation/fab to make the ZF6 work, as well as adapting the LSx ECM to work in the car. Lots of info is out there on doing this, but there is nothing drop-in about it. The sky is nearly the limit with this conversion. Places like Horsepower Research now have reliable LS short blocks that displace over 8 liters, and heads are available that vastly outflow anything you can put on a gen1 engine. It would be trivially easy to make 600rwhp with a very wide power band and good manners, and you could lose 100lbs off the front in the process. This is the no-brainer route to go if you have the money and don't care about originality. It's certainly the way I would go if I were planning a fast C4 project from scratch. But IMO, if you are just going to drop in a 5.3 or 5.7 with stock heads and cam, then this conversion isn't worth the trouble at all. This is the option if you want serious power above what you can reasonably make with Option 2.

Any of these options can be the right answer for you.

 

You don't mean all that torque, akin to say, a BBC?

 

Lets start at the beginning. What are your goals and how much money are you willing to throw at it? If you want to simply toss another L98 at it that is stock, that is easy and cheap. If you want to increase power, you have to figure on gears and probably more. We can't move forward without knowing how much power you want and how much you have to spend.

 

Thanks everyone for your responses

I am looking to up the horsepower to 300-350. Was hoping to keep cost under $5000. I guess at this point I am looking for my best options keeping the same block.

Right now the engine has 119000 miles on it. Was sitting in a garage for the past 8 yrs. Pulled the plugs and are showing rust. My best guess would be that maybe head was seeping and cylinders are rusted.

Plans right now are to pull and tear down.

Any and all input is appreciated!

 

I agree with you approach of rebuilding what you have. However, I suggest that you look in to machine shop availability and cost in your area before you dive too far in to the project. Quality machine shops have all but vanished in my area. And the wait time and cost for the couple that are left leaves me leaning toward doing a crate engine on my next project.

 

At the wheels? A stock L98 probably makes about 200rwhp, so you are seeking anywhere from 50-75% more power. That's a huge increase. It's not going to come from just a rebuild of your 350 with a mild cam and some headers. At the very least, you'll need real heads and a carefully chosen cam. It would definitely be easier to reach your goals with a stroker kit. Basically you've jumped out of Option 1 in my post to Option 2 with your power goals.

 

With that HP as a goal, I would recommend a 383 crate motor. A machine shop could build one for you but you should look at prices of a crate motor versus what a shop would charge to build one. At least, you should talk to a few local shops to see what they would recommend. Can't hurt to pull the motor, tear it down and take the block with you. A shop should be able to determine what can/should be done with your block.

Try Summit Racing or Jeg's for long block crate motors. Also look at warranties; most crate motors will have longer warranties than what local shops will offer.

My '93 autocross C4 has an LT1 383 (still the original block) that was built by a shop. There was some head work done, a cam and true duals with headers. It dyno'd at about 325 HP at the wheels. Not a lot of miles on it, but it runs strong and easily driveable on the street.

 

Thanks for info. I have considered a 383 crate but would I have to do a lot of modifications? If so is there a kit?

 

Here's some 383 engines (both long block and short block) that could be used. You would transfer all of the engine accessories such as starter, distributor, alternator, water pump, A/C compressor, intake, and various brackets and sensors. You could stick with OE exhaust manifolds or go with headers over to a new engine assembly.

Given how long the car sat, I would suggest buying a new radiator, all hoses, t-stat, and water pump. New serp belt too.

Going with a larger displacement (5.7L to 6.3L) would probably make a custom tune necessary.

 

Really appreciate it cruiser. Looks like a really good option. I will definitely check it out

 

I'd find a good dyno tuner. You may have to tow it places. I had to on mine. Back when, only Linfenfelter could do the tune so I had him do it. Since he died, IDK if anyone else in that shop would do it so you have to check if you want them. I take it to Hitech Motorsport in MN. There are others but you should check around. That level of power probably needs you to do some work. Intakes, header and cams probably, if not head work. That kind of work requires a tuning to make the ECM run right. You can have it dyno tuned or have someone guess a tune based on specs and if you are lucky, they can lend you datalogging software so they can fine tune it instead of leaving it guesswork.

 

Oh, HELL YES. Assuming the serpentine belt is still there and intact.

To make 100 HP more, I am going to guess he needs a tune