Tokva

Hi! I am owner of C3 1980 with turbo on it. It goes with 7psi boost what gives about +70hp. I am wondering if someone have experience with upgrading old turbo kit setup on better power with saving original look this vintage treasure?

gearheadib

Is there a wastegate in the system? if so add a boost controller and just turn up the boost.

calwldlife

nice.
looks factory.
what engine?
I am confused on what you are after?

Tokva

It is upgraded L48 1980. My point is it easy modern way how upgraded it with the same outside look... These cars is only few in these days so original is important, but more power is more fun

4-vettes

There's nothing original about that setup so do as you wish! If original is what your after, take the turbo off. It didn't come that way from the factory.

randallsteel

Do you know what your piston ring gap is?
be careful about simply adding boost via bigger turbo or boost controller.
at some point, if the rings are not gapped for the boost level you will break a piston.

speedreed8

Looks like one of those Duntov turbo conversions.

Fly skids up!

Turbo Vette, very cool! Throttle body fuel injection with 2 bar capability and a intercooler. Blow through carbs are a PITA.

Gale Banks 80'

Do You know the History on this car ? Any reason the think a Dealership put this on and sold it new ? Or some other well known installer ? Since it has the L48 Valve covers I assume thats what it is. If so its only has 8 to 1 Compression at best. I believe that the Turbo Kit was made by Martin. And it might of been sold under Accel or some other brands. If so it is not a Blow threw Carb. The Air and Fuel are mixed first and then pass through the Turbo "Wet" and back to the Intake. This was done so that the stock Carb could be retained. like it or not Turbocharged cars spend very little time in boost when driven on the street. So when this thing is not in boost its just a long and complicated path for the Air Fuel to get to the Low Compression Engine that probably has 3:08 gears with a TH350 Trans. This all makes for a car that can't get out of its own way around town but on the Highway can do some sprited passing when the trans kicks down and it makes some boost.
Ok so what can we do with it ? Just normal Hot Rodding. Put in a OD Trans with a lower first gear. Get the Compression up to 10:1. Run a modern FI system instead of the Carb and Distributor that has Boost management.
It would be nice to see whats under the Duntov Cover.

Jebbysan

The very first thing you do with these is unrestrict the exhaust. Remove the Cat.....put the biggest pipe you can downstream to a high flow muffler(s)......ceramic coat the manifolds and anything else that gets real hot......you may even want to wrap some components after ceramic coat.......remove the EGR and block it......put a 180 degree thermostat in it......
Second thing you do is put in a real boost gauge.......these things were maxed at about 5-6psi of boost......and you need to make sure it make all of it or more or it will be a total turd like mentioned above......and a A/F gauge.....
Third thing is to clean it up...replace ALL of the gaskets up top.....I would remove the intake swap it out for a 2101 Edelbrock Performer, the Turbo plenum/diffuser just bolted on top of the stock intake.....and use the 1204 Fel Pro intake gasket to block the nasty hot heat riser port in the intake.....make sure the distributor weights are free and clear, put a dedicated correct boost friendly timing curve in the distributor......send the Q-Jet to Lars and tell him exactly what it is....safe bet he knows what this car is.....
There are conflicting reports of whether or not these were L-82 engines.....most articles say they were.....but I don't think they were......if they were, why did they put stamped steel valve covers on some but not others.....? This is important to know as the L-82 had some very strong TRW forged pistons in it and the L-48 had cast pistons.....which were stronger than one thinks but not boost friendly.....my feeling is ACI slapped the turbo on whatever was available at the time.....the relationship with them, GM and Zora was severely strained by this cars development and ACI just wanted to fulfill the contract and be done with it......

Now from there if you want to go faster......you need to update it to 21st century engine control......which is fairly easy to do now. This would be a great candidate for a full Q-Jet Sniper setup with ignition control.....
I don't remember if these things had any kind of wastegate....but that is a very important part of the system......
2004r or 700r4 trans would be a huge improvement here as these cars were 100% Turd Ferguson from 0-30MPH......until the boost came in it was just an incredibly restricted 350......a 3.42 or 3.73 gear with an OD trans would night and day.....
A pair of modern Aluminum heads with a fast burn chamber would be a welcome upgrade and would allow more boost to be dialed in safely.......and while this is happening put a real camshaft in it if it is in fact an L-48......if it is a real L-82....cam can be left alone.....
The intake should be ported and blended everywhere....as much effort as possible to make the air happy passing through......
A water/alcohol injection system would be huge here too......
I would say that well over 400hp could be had using the same turbo and intake.....

Basically engine control, airflow improvements intake and exhaust, and gearing......

Ironically, the 80'-81' Trans Am turbo suffered from much of the same perils as this car when built but had an even shittier engine and small *** turbo.......a great freakin car straddled with a half baked engine......in the early 90's a neighbor had a 81 Trans Am Turbo with a 455 SD engine swapped in it....rest of the car was bone stock and immaculate.....that was one Bad *** car......and this Vette can be too.....

I found a pic of the same engine with the air cleaner and carb removed......

Jebby

JC 1975

Just out of curiosity, how does this compare to the Rayjay Turbo Kit?

wwiiavfan

Along with the Sniper, I’d be converting it to blow thru the throttle body instead of that long wet path thru the turbo it has now. I’d think that would dramatically improve the response.

Jebbysan

It operates the same exact way......with very similar plumbing but the Rajay uses a dedicated 2 pieces intake manifold and the Martin/Turbo International uses a box plenum bolted right to the stock carb pad.......

Jebby

Gale Banks 80'

I found one of these on e-bay NOS in the Martin Turbo Box. Rejay made the Turbo but I believe this is just a newer Martin Kit than the above.

When I turbocharged my 1980 in 1987 using the Banks Parts ( They were not selling kits at the time, they had no exhaust manifolds ) I did everything right. I built a 7.8 to 1 Compression Ratio, Forged Crank, Pink Rods TRW Pistons, I bought a Porting kit and spent weeks on my 441 Heads. Crower Hyd Roller Cam high tech at the time. Built a Stainless 2 1/2 into 3 1/2 ovel and back to 2 1/2 twin muffler exhaust. (1980 single exhaust Crosssmember) With the Banks supplied Holley 800 Double Pumper and 350 CI. this combination made 474 HP and a bit over 500 Lbs torque on an engine dyno. Ruffly the same as the 502 Crate Motor that had just been released. The guys who did the Dyno were excited at how well it ran right out of the box. Once put in the Car it was a whole different story. When the Engine was idling you could snap the trottle open and it would just bog. I changed a lot of Spark Plugs. The waist gates never opened I had more back pressure in the exhaust than boost.
I took this car to the Nevada 100 open road race where it was in its element with no stop lights or traffic. It did well until it threw a $6 fan belt and DNFed.
After a Garage period of denial for a decade or two I built a new Engine 400 CI 10 to 1 Compression AFR Heads and an Accel Gen 7 to run the FI. 3" true twin exhaust ( I made my own crossmember ) . I now have a combination that runs pretty well in all situations.
This is why I am seeing the above combination having problems. I have seen them them all myself.

69427

Just a few of my thoughts,questions, and opinions:

1) You have a rare Corvette. You can hop it up, but it just takes a bit more thought when boost is involved.
2) As was mentioned earlier, put a wide band O2 sensor on it. You don't want the uncertainly of what your A/F ratio is under boost conditions.
3) Ask Lars for advice on tuning/modifying your QuadraJet. I have zero QuadraJet experience, so I can't offer up any technical advice there.
4) Does your system have a boost wastegate or just a pop-off valve?
5) Does your intake manifold have any bypass valving in the plenum to shunt the compressor section during low load conditions (this helps low speed driveability)? I put a Martin Turbosystem in my '84 several decades ago. It has reed valves in the plenum to shunt the turbo at light throttle, and it drives like a normally aspirated engine at low speeds.
6) What is your present ignition timing curve (ie: does it retard the timing as boost is built)?
7) Also as mentioned earlier, make sure your exhaust system flows well. You will have unavoidable backpressure between the exhaust port and the turbine section inlet, but you do NOT want additional/noticeable backpressure downstream of the turbine section.
8) For now I wouldn't worry about big engine mods. Your present engine ought to be sufficient for a while yet. Years ago IIRC Dave MacLellan (sp?) mentioned that higher RPM centrifugal loads are harder on the pistons and rods than moderate boost levels. (I welcome correction if it was someone else.)
9) Lean fuel mixtures or spark knock are to be avoided like the plague.
10) Consider using a touch smaller plug gap to deal with the boost, as you don't want any misfires out the exhaust or into the compressor inlet section.

That's about it off the top of my head. Have fun, but be prepared to do some reading about turbocharging, as most of your car/beer-drinking buddies won't be of much help.

Gale Banks 80'

I'm not seeing the Reed Valves in what I think is the earlier version, but I think I see them is what I think was the later one. If this car has them, I wonder what kind of shape there in after 40 Years. They don't last that long in Dirt Bikes.

Tokva

This is Duntov Turbo Corvette build in ACI with Mr. Duntov, only about 30 cars was made in 1980-1982. So it is reason, why I am thinking keep it like original, but more powered...

Tokva

Tokva

1,Boost gauge is in the car - goes 5-7lbs
2,A/F gauge I ordered it was one of my first ideas - I am from Europe and here isn´t much peoples with this knowledges like Lars. I newer contact him but I am familiar with Lars name on forum and his instructions about carbs.
3, I am reading in this days about distributor curve, because I really don´t know who can help me here in Czech Republic so I made me into self learner
4, From casting numbers intake is L48 , carburetor also, Heads are 76cc from some camaro - I was thinking about LT-1 heads from 1970-1970 corvette.
5, About Q jet sniper I was also thinking, it is sure best way to go, but I was thinking about staying with carburetor for historical reasons ...
6, I was looking everywhere bud I didn´t find any wastegate and I really don´t understand in this moment how is boost regulated
7, Camshaft was L48 from informations what I found boost goes always with L48 camshaft
8,Water injection was added from " factory" But now isn't working anymore, it is another part what I must found how is plugged into the old system.

In last few days I found son of old owner 40y ago what upgraded engine, another turbo with bigger boost and car was hitting about 500hp, now is back with original turbo and engine from ACI factory, I don´t know why... So I decided make my first trip to USA a try visited old owned and found some "new old" informations

Jebbysan

Well the first thing to do is get rid of this miserable thing.....


And if the cat is still on it.....get rid of it too......first two things. A deliberate intake and exhaust restriction......with a turbo in the center of it......probably the worst thing you could do......and the heat! Heat is your enemy here and was the enemy when this car was in development from ACI.......so many little things that can be done to improve performance.....

Jebby