Building the SFI/Turbo V-6 Vega

Many of my friends on www.V8Monza.com have asked me to document my follow-on project to my previous LT1 Vega conversion. This is the story of my latest effort; swapping a fuel-injected, turbocharged 3.8 Liter Buick V-6 into a 1977 Vega Hatchback.

The idea for this project grew out of the generosity of “Vega Man Larry” Heagren. When I sold my LT1 wagon, Larry encouraged me to pick up another project. I had already been tinkering with a ’77 Vega Hatchback that I planned to purchase from Sherman Wright, and Larry had a complete ’81 carbureted Turbo set-up that he had previously run on another Vega. When I sold the LT1 car to Sherman, acquiring the ’77 Hatchback and low-mile V-6 engine were part of the deal. My plan was to get the car running with a V-6/Quadrajet set-up. I had a couple parts that Larry wanted to upgrade his brown ZZ430 car, and I asked what we were swapping—Larry replied “How about the Turbo set-up?” I was shocked, because I knew he had a lot of money invested, but he insisted that it would be a good basis for my next project, and that his wife wanted him to “get it out of the garage”. So, I inherited several boxes of Turbo parts, including intake and exhaust manifolds, plenum, an MSD6AL Boost Timing box, and the turbo itself. It was basically complete except for the carburetor. I got busy learning all I could about early Turbo Buicks and the 3.8 V-6 Vega conversion. My plan was to get the car running with the naturally-aspirated V-6, fueled by a Quadrajet carb, then build another V-6 with the turbo parts and do a swap. This time, I would all the work myself, except building the engine and transmission.

'77 Vega with NA V-6

N/A V6

N/A Engine with Stock Monza A/C

Monza A/C in Vega

Living in Texas, I had already decided the car would have air conditioning. This was a challenge in a car that had come from the factory without A/C. I decided to replicate the stock Monza wagon set-up as closely as possible, so I traced the outline of the A/C holes on the firewall from a car in the junkyard to a piece of cardboard, then transferred that to the Vega firewall and cut them out with my Dremel tool. I also had to cut the blower fan plenum opening behind the firewall and under the dash. Some of the earlier HO-7 Monzas used a cover plate to seal off the A/C opening after the HVAC core control box was installed, so I found one from a Starfire Hatchback that would work and installed a stock system from parts I scrounged from other H-body guys, eBay, and the local wrecking yard.

I found another early Buick engine and set it aside as the basis for the Turbo motor. I planned on using the stronger turbo crankshaft with rolled and filleted main and rod journals, and a set of .040-over forged aluminum pistons. I found most of what I needed by watching eBay and the Turbo Buick “Parts for Sale” message boards. In the meantime, I worked on my basic V-6 Vega project while I was sitting standby reserve in Louisville, KY for my job as a UPS pilot. I started to build the car up from a rolling shell in fall, 2003, and had it running and driving by March, 2004. But even though the V-6 was supposedly recently rebuilt, it was obvious whenever I put a load on the engine that it had a rod knock. I didn’t want to drive the car back to Texas like that, so I borrowed Sherman’s trailer and towed it home in fall, 2004. I sold the extra engine and planned on rebuilding the engine that was in the car as the turbo engine. When the car got back to Texas, I pulled the engine, broke it down to a bare block, and took all my parts to Samford Racing Heads in Abilene. Mark Samford had earned a good reputation as an engine builder, especially among the local Turbo Buick crowd. I gave Mark all the engine parts I had gathered, and we agreed he would fit the engine in to his work between other projects so I could stretch out payments and stay “on budget”.

In the meantime, I learned a lot about Turbo Buicks. The ’81 set-up was the least desirable among the early carb/turbo designs because it used a normally-open wastegate instead of the normally-closed design. I would either need an M4ME electronic feedback Turbo carb, or I would have to find a way to make a manual carb power valve go full rich under approximately 4 p.s.i. of boost. The ’81 and ’82 exhaust manifolds were more restrictive than the other years.

Exhaust Manifolds (top to bottom) ’83-85 (’86-’87 similar) ’81-’82 (Smaller Outlet) ’78-80 (same outlet diameter as ’83-’85)

Although I enjoyed the technical challenges this presented, obviously, this was not going to be a high-performance screamer. The Buick carb/turbo design did not lend itself to a good, uniform flow to the outboard cylinders. The boosted fuel/air mixture just dumped into a center port from which all the intake runners were fed. Although I found a great NOS non-electronic Q-jet carb and devised a way to make the power valve go rich under boost using a Hobbs switch and solenoid, I recognized the weaknesses inherent in the early Buick design. I started looking at the ’84-’85 fuel injected Grand National set-up that replaced the carb/turbo Regal. The turbocharger was in the same general location as in the earlier carb/turbo set-up, the exhaust manifolds were the same design and fit in the same location, the up-pipe, down-pipe, and crossover were essentially the same. All the major differences were above the heads, so I knew it would fit in a Vega as well as the carb/turbo set-up. The Sequential Fuel Injection (SFI) Turbo intake manifold also had a better flow design. Although the ’84-’85’s were not intercooled like the later Grand Nationals, many of them were turning high-12 second E.T.’s on pump gas. Clearly, this was what I eventually wanted in my Vega.

'81 Turbo Buick Manifold Set-up

Electronic Power Valve Control

And then it showed up on eBay—not complete, but the basic foundation was there. A rebuildable turbo, throttle body, intake manifold, fuel rails, and injectors from an ’85 Grand National. I told my wife she was getting it for me for Christmas, and I felt like I stole it when I won the auction for $130, plus shipping!

'85 Turbo Manifold (example)

'85 Turbo Buick SFI Engine (example)

When Mark got ready to start on my engine, we hit the first snag. I had a set of .030 forged TRW pistons I purchased for the engine that was sold. The engine with the rod knock we pulled from the Vega had been previously rebuilt and bored .040-over! Since forged Buick pistons aren’t available in .040-over, the best option was to find another stock block. Other than the Stage I and II blocks, the strongest blocks in the Turbo Buick cars were the -109 blocks that were used from mid-1985 through the end of the production run (also used in the ’89 Turbo Trans Am). It is increasingly difficult to find a good Turbo -109 block that hasn’t been thrashed, overbored, rebuilt, or abused. When you can find them, they command a premium price. Fortunately, the naturally-aspirated V-6 1986 and 1987 GM RWD cars all used the same -109 block with one minor difference—the turbo oil drain hole on the front of the block was cast solid. Other than that, the block and heads are identical. I went to my local wrecking yard, and located six potential donor cars with -109 blocks, and settled on a 1987 Grand Prix as the best candidate. I gave the owner $150.00, and he delivered it to my home. Twenty-four hours later, I had the block completely disassembled and took it to Samford Racing Heads as the bare canvas for my new Turbo engine.

The engine is built around a standard “-109” Block from a non-Turbo 1987 Grand Prix. The pistons are TRW Forged .030-over. Connecting rods are standard Turbo Buick -763 castings with ARP bolts. It is balanced at 38%. The Main Bearing caps are held in place by ARP studs. A double-roller timing chain replaces the stock unit. Heads feature a 3-angle valve job by Mark Samford; style='color:black'>Manley "severe duty" 1.71" intake and 1.5" exhaust valves are used with LT1 springs at 105 lbs. seat pressure. ARP head studs are used to fit the heads to the block. The Reed cam uses profiles from Sod-Buster 4H260 intake (210@.050”) with a Torque-Master TM252 exhaust (205@.050”).

The engine uses a drivers-side polyurethane mount from RJC Racing to control torque, and a standard rubber on the passenger’s side to dampen vibration. The transmission mount is a standard Energy Suspension TH-350 polyurethane mount from Auto Zone.

'85 Intake and Exhaust on Bare Block

'85 Turbo Intake and Exhaust Plumbing

Having put the fuel injected LT1 in my previous Vega, I felt comfortable with fuel injection, sensors, wiring, and computers. The ’84-’87 SFI/Turbo was an early second-generation design, but it basically used similar sensors and design logic as the LT1 and even the current LS-series engines. I spent countless hours on the Turbo Buick message board sites, and found one fantastic source— www.gnttype.org has more good information in one location than any site on the web. One of the first things I learned was that since the earlier computers were more rare and expensive to replace you could set up the earlier ’84-’85 engine with the ’86-’87 computer. Even more interesting was the fact that the same basic computer was used with a different replaceable chip in many of the FWD 3.2 and 3.8 liter V-6 cars built by GM between 1986-1989. If the computer was the same, the engine control wiring harness would also have to be very similar to the SFI/Turbo harness. One improvement over the ’84-’85 ECM and harness is that the ’86-’87 set-up added a manifold air temperature sensor for improved throttle response and lower emissions. Since I didn’t have a Turbo donor car, and I didn’t want to pay $600.00 for a custom harness, I decided to pull a computer and harness from a 1987 Olds ’98 Supreme and start modifying. I compared the wiring diagrams for an ’86 Buick Century FWD car to the ’86-’87 Turbo Regal and found it only required changing about five wires to make it work. You can find the wiring diagram for the Turbo Buck here: http://www.gnttype.org/techarea/ecmsensors/regal_ecm.jpg. I added a connector and wiring for the Turbo Wastegate Control Solenoid and spliced the Third gear and Fourth Gear (2004R) input wires together take an input from a third gear pressure switch from the TH350C transmission I am using. This not only allows torque converter lock-up, but also provides timing and boost adjustments to the ECM. The ’86-’87 cars (FWD and Turbo Buick) have provisions for electric fans, but I decided to stick with the mechanical fan set-up that came on the ’84-’85 Turbo Buicks and eliminated the extra fan wiring and relays. All the ECM wiring is on a dedicated fuse and relay circuit from Painless Wiring. Power for the engine control harness comes straight off a 12-gauge hot lead from the battery to a relay that is activated by the existing Vega 12-gauge pink"Ignition Hot" lead. Three fused feed lines tie into the ECM and sensor wiring from the relay. That way addaitional loads are not placed on the Vega wiring. Follow this link for more on swapping to the ’86-’87 ECM and harness: http://www.gnttype.org/techarea/ecmsensors/8487ecm.html . I decided to use a used stock prom for starters, and I bought a CALPACK chip from www.GMPartsDirect.com. Another popular electronic upgrade is to swap to the later 3-coil pack used in late ‘80’s through mid-‘90’s GM FWD cars. This is a simple upgrade; read about it here: http://www.gnttype.org/techarea/ignition/type2coils.html .

The older GM ECM cannot be exposed to temperature and weather extremes like the newer ones used in the LT1 and later vehicles. This required me to locate the computer inside the car. I found an old Turbo Regal RH kick panel that had provisions for mounting the ECM and modified it to mount behind the console. I used a Dremel tool to cut a hole in the firewall and a rectangular computer desk grommet to pass the wiring through and close the hole.

One of the weaknesses in the earlier SFI set-up was the Mass Airflow (MAF) Sensor. They had a tendency to fail, and were expensive to replace. Fortunately, the later LS1 MAF is more reliable; flows more air, and can be used with a device called a MAF Translator to work with the Turbo Buick ECM. I decided to go with the MAF Translator Plus, which also allows some custom tuenability for spark and fuel delivery by modifying the MAF signal to the ECM. Read about how it works and how to install the MAF Translator by clicking here: http://www.ramchargers.com/RamNews/Translator/index.htm .

As mentioned earlier, many of the exhaust parts from the ’79-’83 carb/turbo Regals will interchange with the ’84-’85. I experimented with the stock tubular headers that were used in ’83-’85, and concluded that they did not provide enough clearance. I found a 1980 Turbo Monte Carlo at my local wrecking yard, and I decided to use the exhaust manifolds, crossunder pipe, and, turbo up-pipe from that car. They fit nicely without hitting the fender wells and are the same inner diameter at the exhaust flange as the tubular manifolds. Because the ’80 manifolds were from a pre-ECM car, I had an oxygen sensor bung welded into the up-pipe. I had the manifolds coated with a black heat-resistant powder coat, and painted the up-pipe and crossunder pipe with Eastwood Silver 1200 degree manifold paint.

As I learned in my first project, fuel delivery is one of the major costs and headaches of doing a conversion to fuel injection. I wanted to use a stock Vega fuel tank and sender, so I was able to extend the existing pump bracket to take a Walbro 340 255 LPH pump. I had to make some wiring modifications to allow the pump to work with the Vega wiring to the top plate, but got solid contacts and grounds. I had a local radiator shop add a 5/16 inch return pipe to the top plate, and braze 6AN male fittings on the ends of the existing supply pipe and new return. Since I didn’t add a baffle to the tank, I needed to ensure a constant fuel supply under lateral acceleration. I found that Walbro made a multiple pick-up system (also sold by Holley) that used check valves to prevent cavitation. I threaded a brass hose nipple fitting into the plastic end of the pump pick-up below the screen and connected three pick-ups into the fitting with 3/8 inch fuel hose. If you need to put a piece of high pressure hose in your fuel tank, be sure it's rated for in-tank use [SAE J30R10].   Your typical parts store high pressure EFI hose is only rated for outside the tank used [SAE J30R9].   That hose will turn to mush in no time. You will also need to add some type of fuel pulse damper to prevent the pulsation caused by the injectors cycling from causing excessive banging and possibly damaging your fuel system. I found the same kind of corrugated tubing GM uses in the canister-type fuel modules in late-model EFI vehicles at Auto Performance Engineering (http://www.autoperformanceengineering.com/ ) . The secret is not to cut the tube, but leave it long and create a loop in it between the tank pick-up line and the pump output nipple to act as a “bungee cord” in the fuel system and reduce pulsation shock.

Fuel Tank Pick Up

Fuel Pulse Isolation Tube

I pulled the existing Vega fuel lines, and spent an afternoon hand-bending two 3/8 inch aluminum lines that closely matched the bends in the Vega lines. I used Russell 6AN male hard line fittings on each end. These were mounted in place with the existing vapor line using rubber padded brackets. Sherman and I then went to a hydraulic supply shop in Odessa, TX; and found reuseable steel fittings and 200PSI fuel-proof braided hose for a fraction of what it would cost to order similar parts for Jegs or Summit. (We even got enough to do the oil cooler lines!) We had to use 8AN with 6AN female adapters, and we needed two 45-degree ends, but we were able to make our own hoses to connect the tank to the supply and return fuel lines and those lines to the fuel lines coming off the engine fuel rails.

Fuel Pump Assembly

Supply and Return Fuel Lines

One of the popular upgrades to the Turbo Regal is a “Fuel Pump Hotwire Kit”. It uses the existing 16-gauge fuel pump power wire to actuate a relay connected to a 10-gauge wire straight from the battery to the fuel pump power connector. These are available from many companies, but the least expensive is from Full Throttle Speed: ( http://www.fullthrottlespeed.com/ ) . Because of the age of the wiring in the Vega, I decided this was something I had to have. You can read more about the installation by clicking here: http://www.installationinstructions.com/102028.pdf .

Transmission

The transmission I selected is a Buick/Olds/Pontiac TH350C with a 2800-stall lock-up converter. It was rebuilt by Ronnie Smith Transmissions and features Kevlar clutch packs and a hardened input shaft. The advantage of the TH350C is that it is cheaper and stronger than a stock 2004R, it fits in the Vega chassis without modification unlike the 700R4, and allows the use of the stock torque arm. The Buick ECM takes a signal from an internal 3^rd gear pressure switch and sends it to the 3^rd and 4^th gear input pins of the computer to make timing and spark adjustments. The computer controls the 12-inch heavy-duty lock-up converter with anti-balloon plates and heavy-duty clutches from Pat’s Performance Converters.

Since the Buick ECM can use a vehicle speed sensor input, I put a JTR Conversions 12PRS two-pulse VSS drive between the speedometer cable and the speed drive on the transmission. This is highly recommended for a street-driven car, because it prevents stalling when the car is coasting to a stop and at idle.

TH350C BOP

The rear end is a stock Monza unit with 26-spline S-10 rear axles, a 2.92 Monza gear set, and an S-10 posi unit. The torque arm is from a stock V-6 Monza application, so it did not need to be shortened or modified. I used a polyurethane bushing to reduce wear and play in the torque arm mount.

7.5-inch Rear End and V-6 Monza Torque Arm

Lubrication and Cooling

I am using a re-cored 4-row Monza copper/brass radiator with an internal transmission cooler for the time being. I will eventually replace this with an aluminum radiator with internal transmission cooler. A V-6 Monza Towne Coupe fan shroud provided both a top mount and minimizes air loss around the fan. A 7-blade flex fan replaces the stock steel fan used on the ’85 Grand National engine. Since the turbo is not intercooled, maintaining a good supply of cooled oil to the bearings is critical. Oil is supplied to the turbo from the port on the block where the oil pressure switch fits on a non- turbo engine. The oil pressure switch is retained by using a brass t-fitting. Another t-fitting is used to fit the oil pressure gauge sender where the oil feed line goes into the turbo housing. I am using a Kenne Bell High Volume Oil Pump kit with an aluminum spacer, longer gears, and a steel thrust plate. The oil flows through a sandwich-type Grand National oil cooler adapter and through an oil cooler in front of the A/C condenser.

Oil cooler

Vacuum

Since a couple of the vacuum ports were damaged, I replaced the plastic vacuum block on top of the throttle body with a billet aluminum piece from John’s Performance. Since the ’84-87 Turbo Regals used an electric Powermaster brake booster, the normally-unused large port on the vacuum block must be used to supply vacuum to the Vega power brake booster. The Turbo Regals only use a Manifold Absolute Pressure (MAP) sensor to supply boost information to the digital dash boost gauges. The MAP sensor is not used by the ECM. I replaced the MAP sensor with a mechanical vacuum/boost gauge that takes its signal from the back of the intake manifold plenum after the air is turbocharged. (NOTE: The vacuum modulator must not see boost pressure. DO NOT HOOK THE TRANSMISSION VACUUM LINE HERE!) I also incorporated a boost light off a Hobbs pressure switch that comes on around 4 psi. Vacuum connections are shown in the diagram below.

Instrumentation and controls

The stock Vega GT dash is retained with some added features. As mentioned, a two pulse JTR Vehicle Speed Sensor is used at the transmission speedometer pickup to send a speed signal to the ECM. The speedometer cable then attaches to the VSS. Tim McCabe reprogrammed the tach for a V-6. The tach signal comes from the white tach wire on the ECM. The coolant temperature gauge is stock with the standard sender installed in the upper intake manifold. I used a stock AMP gauge rather than a volt gauge. I added an Autometer mini oil pressure gauge in the clock location with the pressure sender pick-up coming of the right galley plug in the back of the block. This required some ingenuity and tube bending. Fortunately, Sherman Wright knew exactly what kind of fittings were needed, and figured out how to route the lines so the sender would be at the top rear of the block We used a ¼” brass pipe fitting into the block with 90-degree elbow and a brake flare fitting on the other end. This goes to a 5/16” steel brake line, then out through a hole in the block flange to an adapter that the sender threads into. All “idiot light” functions are retained. A Check Engine light is mounted in the clock stem hole. I epoxied a single gauge pod onto the left A-pillar cover to house a vacuum/boost gauge and a boost light. The Assembly Line Diagnostic Link (ALDL) from the ECM is mounted under the dash near the ashtray. A Torque Converter cutout switch is mounted on the center shift console to disable automatic lock-up. This ties into a four-pole brake light/cruise control interrupt switch that interrupts the lock-up signal to the torque converter when brakes are applied.

'77 Vega Dash and Console Mods

Vac/Boost Gauge Detail

Door Panel

Axles and Brakes

The front spindles, rotors, and calipers were swapped for a set of low-mileage 2002 S-10 pieces (with provisions for ABS). The rear axles were swapped for S-10 axles; the drums are new replacement S-10 pieces, and the rear brake cylinders were upgraded to new replacement S-10 ¾-inch bore cylinders. The master cylinder is a new 1992 S-10 replacement cylinder, and I retained the Vega proportioning valve. If you want to read more about how to convert to a five-lug front and rear suspension, go to www.v8monza.com .

Wheels and Tires

In “Building the V-6 Vega” by John Thawley, there are several pictures of a Vega with 13” American Racing “Vector” wheels. These were used on a variety of cars in the ‘70’s and ‘80’s; most notably the Dodge Charger and the Buick Grand National and Turbo T-type. Because they looked so good on the cars in Mr. Thawley’s book, and they fit the Turbo Buick theme of the project, I decided I had to have a set on my car. They have been out of production for quite some time, and are getting expensive and hard to find. Fortunately, the “Dukes of Hazzard” movie has brought them out of the woodwork; and by doing a search for “General Lee Wheels” on eBay, I turned up a set of Appliance Turbo wheels with the correct GM 5 x 4.75” lug pattern. The front wheels are 14” x 7” rims, and the rears are 15” x 7”.

American Racing Vector GN Wheel

Steering and Suspension

A standard H-body Saginaw power steering box is coupled to a Monza tilt column by a Flaming River needle bearing universal steering coupler. The Vega front sway bar was replaced with a heavier, 1 1/16 inch Monza unit, and the rear sway bar is the standard 7/8 inch H-body piece. Delco offset upper control arm bushings were installed to cope with camber issues. The upper ball joints are S-10 type, and the lowers are late-model H-body replacement pieces installed using Bob Gumm’s ball joint adapter kit.

Steering coupler

Body

The hood is modified with a cowl-induction scoop to provide clearance for the turbocharger. A front air-dam/spoiler replaces the stock Vega air deflector under the front lower valence. A rear deck lid spoiler is mounted on the hatch. The radio antenna is an electronic antenna mounted on the rear of the roof line as seen on modern sport/touring coupes. The 1977 black window bezel treatment is used instead of the polished aluminum from earlier Vegas. The rear taillight panel is blacked out like many of the Chevy SS models of the mid ‘70’s. Bumpers are painted body color, with the stock black rubber strips.

Turbo Vega Body Concept