Hello and thanks in advance to anyone that can help me out.
I currently have a 1989 Corvette convertible with an L98 5.7L... It has over 200k on it and is not doing very well so it's time for an overhaul. I recently came across an L31 5.7L... out of a 1990 Silverado with under 100k and the guy is willing to let it go for super cheap. So my question is what is my best/cheapest/least time consuming option. I'd rather not rebuild the L98 cause I don't really have the time but I don't want to sacrifice too much power by just dropping the L31 in (assuming that is even an option I'm really not sure). Anyway thanks again and If you need any more info just let me know.

 

I would just have your stock engine rebuilt, it cost about $1,600 here to have a stock rebuild done..You would probably have to get a new tune done with the L31.... Personally I wouldn't put the truck engine in....WW

 

getting your engine rebuilt may be a pain for you but in the end you'll know what you have.

 

I have had the rebuild priced out at right around $1500. I know it is the best option but I guess I'm just seeing if there is a decent alternative. The guy told me I can have the L31 for $150 if I pull it out myself so I'm just looking at the options cause it is such a good deal. that said if the overall consensus ends up being don't do it I definitely won't. Any details as to why not to/or if there is a best way to do it would be appreciated. thanks

 

Keep it #'s matching, in another 30years someone will appreciate that you did. There are people on Craigslist (and E-Bay) letting high-performance strokers go pretty cheap, in this economy people don't have enough money to finish projects and that works out for people like us (Gear-heads). This is how I aquired my car, a guy in N.J. lost his job and him and his wife were gonna try fresh down south and were selling thier house too. I didn't know all of this when I looked at the car and kinda felt bad, but if not me, somebody else.

 

Ive had an add up on kijiji (canada's craigslist) for quite a few months now and this is pretty much the best offer I've been presented with. Keeping the #'s matching is a very good point though. As far as the economy goes... These corvettes are for sale all over for 8-9000 with 100k less than mine makes it tough to justify spending almost 2grand on it.

 

Yeah, but you'll know what you got and it's always gonna be a VETTE CONVERTIBLE and don't think for one minute that one of THOSE wouldn't need a ton of work even after you paid 10 grand for it. Keep the original motor on a stand and rebuild it down the road and put it back one day or sell it as is with the car in the future if you don't keep it for life.

 

You can always pick-up a fresh high-pro short block for around a grand and just transfer your stuff and reseal the heads, I've done that in the past.

 

Ya I'm pretty much just trying to find a way to avoid the inevitable.

 

Listen, no matter what you do, once you pull that engine you have the chance to make your car a beautiful thing. New wire looms, a degreased engine bay, repainted brackets,valve covers, runners, plenum and on and on.......and it'll be worth it because it's a VETTE and it's a CONVERTIBLE!!! Check out my cars pics, I got that car that nice and I didn't pull the engine, so imagine what you can do. I mean don't get me wrong, I spent a few grand on a lot of parts and a hell of a lot of work, but I bought the car in October and got this far in 5 months, I think it looks awsome and it runs & drives like new. Take your time, have an eye for detail and reap the rewards come the summer.

 

The biggest problem is like I mentioned in my first post, the fact that you will have to have a completely new tune done for a different engine. I don't know if you are up on what is involved with tuning a new engine but if you don't have the parts already you will have to buy them to do a tune, this will cost about $150.00 plus the price of a laptop computer if you don't have one already, plus a tune takes awhile to get done .. If you don't have the knowledge how to do a tune ( which most don't) you will have to pay someone at least $150.00 to do it for you...This is the main reason to stick with your engine , you can have it rebuilt , drop it in, and not have to worry with any tuning...Believe me, it takes less time for someone to rebuild an engine, then to do a complete "good quality" tune..WW.

 

Hi guys. I'm new here today and I saw this post. I have already done this conversion on my 89 tpi motor, only I bought a brand new GM L31 shortblock from GM. The new shortblock comes less camshaft, so you simply swap your in and the tune stays the same. I was able to get summit to sell it to my for $1500.00 as I found SDPC was selling it for that, and sold my old shortblock for $250.00. I simply swapped my L98 top end over (actually I added a few things while I was at it) and now have a brand new L98 (stock cam but 1.6 roller rockers and a mild tune) for not much more than a rebuild. Just thought I would throw that option out there for you. Incidently, my L98/700R4 combo is in a 1989 Jaguar XJS convertible. Just to be different.
Rob

 

Don;t go cheap.
You pay three times over at some point down the road. Rebuild your original block and build it with good parts that will be the platform for any future upgrades. Numbers match, you know whats in there.
Someone selling cheap always sells cheap for a reason and I can assure you that its NOT because they are there to help. They are there to off-load a piece of crap.

If you can pull the motor, you can start picking up on parts over the weeks prior, and have it all in hand when you take the block to the machine shop.

BTW
You will benefit in longivity if you have the machine shop internal balance the rotating assy. It last longer and will let it rev higher, faster, smoother. I watched my machinist balance each part by brushing off a grain or 2 or material, then balancing pistons on rods so they all matched with each piston going to a hole that it was fitted to.
This build is getting close to 200K and no oil burning and still jumps sideways if I stand in it....

Rebuild, restore.
oh yeah, let go of the "blue book" attitude. Corvettes may be valued in the blue book but they do not follow the book in sales. They are collector cars and people will pay 3 times what book value is if they see one they love. Blue book is for passenger cars and trucks, NOT Corvettes.

 

I LOVE THIS CAR!!! I almost bought one of these before I bought my vert, how hard was this conversion? DAMMM thats nice

 

Don't let everybody here scare and confuse you, do whatever your budget allows. As far as tuning, it's not that big of a deal or expensive if you do your homework. Do alot of reading (knowledge is power), buy a used Snap-On 2500 OBDII scanner( which reads I & II and has a I adapter) and a good voltmeter, then learn how to use them. The scanner allows you to properly adjust the tps, re-set codes without removing the battery, check emmissions (among other things) and can be used on any other cars you'll work on. I got mine on E-Bay (I won the auction) for $325 and it was a steal, I got tons of adapters and cartridges, then I added other things I could use.You can check, clean and re-use everything you have, then dial it all in. The right tools pay for themselves and stay in your tool-box forever. READ, READ, READ, I spent the first 2 months I owned this car reading and doing my research.... And a lot of people here helped me out(Agent86 knows his stuff) Just filter out the things that don't apply.

 

I'm willing to help you out....

I don't know what you found but if it came out of a 1990 truck it's not an L31. The L31 didn't begin production until 1996.

Most likely it's a TBI engine.... The block itself is the same as your L98, but it has, low compression pistons, a flat tappet cam and crappy high swirl cyl heads.

As stated by WW7, rebuilding the L98 is not that expensive.

Will

 

I don't want to hijack this thread, so you can PM for more details. Its not a huge issue for this swap, depending......................