The C3 'vette has long been, in my opinion, one of the best-looking cars. So how happy I was when I was able to buy a 1981 midnight blue C3 when I was 20. I found a great deal from a guy that bought one for his daughter, who quickly lost interest when she found out her father wasn't going to do the maintenance.

After a year or two of having fun just driving the thing, I needed to do some engine work. I started to pull it, and then life started happening. I had a child, so it wasn't reasonable to use that as a daily driver, so I got another car. Started adding more children, my expenses started piling up. So the 'vette just became garaged.

Well, finally, 10 years later, I'm at a point where I can start working on my car again. Yeah, it's been parked that long.


I'm aiming for a street-friendly engine putting out 500-600hp. I am considering single or twin turbos, probably twin since it require shorter pipes from the exhaust to the turbos.

Reliability is a big factor and so I want to spend extra to build a stout engine. So a forged rotating assembly seems reasonable.

If I'm planning on turbos, I figure static compression should be around 8:1, which is about what the stock motor had anyways. Of course, power will be greatly reduced at such a low compression until I get around to putting those turbos on there, but I can live with that for a while. (I just want to get back to driving the thing!) I'm interested in using the turbos both to increase the power as well as increasing the thermal efficiency of the engine.

It's going to be bored/stroked to be a 383.

This is a fuel injected engine; I have an LT4 I'm going to be modifying.

What I could use some advice on is cam selection. I simply don't know enough about all the variables involved. I understand what lift means as far as how it affects the valves, but not how overlap, separation, etc. affect drivability. I'm more interested in a smooth idle than ridiculous top-end power. I want to enjoy taking this for a cruise on the highway.

I know I can ask Comp, Crane, etc. for the best cam, but that won't tell me what it's like to drive it. So, does anybody have experience with a streetable turbocharged engine cam selection?

 

Just my opinion but I'd stay away from turbos. They are great until after 30,000 miles then they will start to deteriorate. If it were me and I wanted forced induction I'd go with a blower but that's just me. I know hood clearance is always an issue with roots style blower but there are belt driven centrifugal blowers out there that you can fit under the stock hood.
You cam selection should take into account that you will be using forced induction at some point.

 

What are your plans for brakes and suspension? Welcome to the club.

 

Well since I'll be spending so much money on the drivetrain I figure I'll cut a hole in the floor and Fred Flintstone it.


Actually this is something I'll need to do more research on to give an honest answer. I had looked into this stuff years ago when I was first starting to work on it and so my research is a bit old and my memory a bit bad.

All the bushings and what-not need to be re-done simply because of their age. Probably going poly.

I'll look into upgrading the rear end to a six-link setup. At least, that was the go-to thing a decade ago. Offset trailing arms because I want to run a somewhat wider tire in the back without having to flare out the fenders too much.

Low-profile tires. Not crazy, 1" of rubber low profile tires, but something lower than the "fat" stock tires.

Brakes are a bit of an unknown at the moment. This isn't going to be a track car that's going to see a lot of rapid acceleration followed by hard braking, so I don't think I need to go crazy with ceramic everything, but I would like to upgrade, if only for the cosmetic improvements.

I'm torn about the rear monoleaf. I know there are plenty of vastly improved setups out there but I do rather like saying, "I've got a spring made of fiberglass!" The front I'll probably go with coil-overs. BUt again, I need to do more research there for current knowledge.

 

I recently started a thread on Best and worst mods so take a look there for some ideas.

I have a small roots blower. Weiand 142. Personally I love it. You MUST build the motor accordingly. Carb, cam etc. That being said, you can build a wicked normally aspirated engine. Several on this forum have done so. 500-600hp is going to likely require high octane gas, or like me if supercharged, that and/or methanol injection.

Im not sure on the turbo reliability. But honestly all my modified motors I,,,,,,, well drove like modified motors. Things break. That being said if it is designed and built well and not taken to the drags every weekend you will get years of fun out of it.

 

I've seen some of that thread.

Nothing against the roots blowers, I just want to keep looking as stock as possible from outside the hood, so no scoops. It'd be different if I was building it for the track. Centrifugal is an option, but even with all their complexities I still tend to lean slightly more towards turbos. If I was just wanting bolt-on power I'd probably go with a centrifugal supercharger, but since I'm building the engine from the bottom up I have room to build it properly for a turbo setup.

High-octane is fine. I'd prefer to keep it pump gas, though.

 

I'm guessing that LT4 is out of a 96 vette with the much loved optispark. You can make the 500hp w/o a turbo or blower as there are several 383/396 builds you can find on the net. I would look for a replacement for the optispark to include with the build. LTCC and EFI Connection make alternatives, with EFI Connection making a kit that allows the use of a 411 (LS1) PCM, way easier to find someone that can tune this than the LT4's computer. If you price out building this LT4 you may find its close to swapping in a 6.0 LS engine. More support for the LS platform than the LT1/4. Lots of decisions/choices, wish you the best.

 

Yeah I've had my eyes on the LS series as well. 10 years ago when I bought the LT I got it and the transmission for 1500, and the LS series was hard to come by at that price point. But now, they've fallen in price so much. I would certainly benefit from the new tech in the LS series compared to the LT. Do you know of a good place to compare the differences in the LS series? I can find LS out of trucks pretty easily but I imagine they're cammed differently.

 

I don't know of a site that lists every difference between the 4.8, 5.3, 6.0 LS car & truck series. The car LS has a different intake and probably a different cam. Since they are hyd rollers, you can swap cams and not worry about the lifters. I'd search for a truck engine, way more trucks made. There have been a few very detailed LS swaps on the forum that you could learn a lot from. These guys have solved the problems with the swap already, it'd make the swap less stressful. There is a lot to be said for having a hot rod that you can plant yourself in the seat and drive and enjoy vs the old days of constantly working/tuning on it, modern tech gives you a hot rod with less maint and more performance, win win.