Reviving a Classic: The Cutlass LS Swap Journey

History of the Oldsmobile Cutlass 

In 1978, the United States was amid the 70’s oil crisis, and General Motors was putting out generic gas-sipping vehicles. Cue the Oldsmobile Cutlass and the beginnings of the G-Body platform that would be manufactured long into the 1980s. Car enthusiasts wanted performance vehicles; we received a variety of nearly identical G-Body’s spread across the lines with minimal performance on tap. Over the next decades, the iconic G-Bodys gained a following in the racing world from drag racing, dirt, and asphalt.

 

UMI Performance Upgrades A 1978 Cutlass 

At UMI Performance, we make top-quality performance products for a range of platforms. Our products are made from American steel and manufactured in our Pennsylvania facility. We test-fit all of our products and test them at our official testing site, UMI Motorsports Park. Among this fleet of awesome cars, we have our 1978 Cutlass equipped with products from our 1978-1988 G-body product line.

You can watch us upgrade our Oldsmobile Cutlass’s suspension in season 1 of our G-body build series. With the stock parts out of the way and a new Stage 2 Power Tour package installed, this car handled like new! With a brand new set of 18″ x 9.5″ RB3Cs Forgeline Wheels wrapped in Michelin Pilot Sport 4S 275/35ZR18s, this car had never looked cooler or been planted better.  At the conclusion of our first season, the Cutlass had a great baseline of performance handling, and the transformation could have been complete, but we decided to go the extra mile and add a bunch more power.

UMI's 1978 Cutlass and Stage 2 Handling Kit

Season 2: More Power = Better Engine! 

In season 2 of our G-Body Build Series, we set out to take our Cutlass to the next level, with a new engine, and all of the supporting modifications to make it a reliable cruiser. Considering the low miles on our Cutlass, we had no problem stripping the engine and transmission out within short order. Initially, the Olds was powered by an underpowered 260ci V8 backed by a 3-speed 200 Metric transmission.  

With our power plant carefully removed, we also tackled the removal of the factory steering components and the cooling system to make room for some performance upgrades. Lastly, we put some elbow grease into the cleaning and some painting in the engine bay to prepare the car for the transformation to come.

Putting the Power to the Ground

One stipulation with this build was keeping the center console and the factory interior. For this reason, we made the call to continue with an automatic transmission. The factory 200 Metric transmission was tossed in the scrap pile while we searched for a stout replacement. We contacted our friends at Bowler Transmission to discuss our goals. After hashing out our options, we chose a 4L60E Tru Street Transmission with all the needed installation accessories. The transmission was delivered with the proper converter installed, and after installing the supplied flexplate, the 4l60E was mounted in its new home thanks to our newly designed transmission cross member. With our engine bay layout, we opted to add a Lokar Flexible Transmission Dipstick to make filling the trans less of a chore. We worked with the guys at Shiftworks to put together a trick shifter cable to allow smooth shifting with our G-Body Parts short shifter to control gear selection in our Bowler 4L60 Transmission.

Our rear-end choice was a simple one. Many of our customers are putting Quick Performance rear ends into G-Bodys to replace the factory 7.5″ units. Our personal experience with Quick Performance in the past made this the only logical option. Ashton at Quick Performance sent us a burly 9″ rear built to our specifications. Installation was a quick bolt-in using our upgraded rear trailing arms. We made the call to upgrade from our Season One suspension package to something more adjustable in the rear. Roto-Joints are our go-to upgrade for rowdy street cars, so we opted for UMI Performance 1978-1988 G-Body Double Adjustable Control Arms with Roto-Joints, 1978-1988 G-Body Adjustable Upper Control Arms with Roto Joint, and 1973-1988 GM A/G-Body Polyurethane Rear End Housing Replacement Bushing. For dampening duties, we installed our new 1978-1988 GM G-Body Rear Coilover Kit specifically designed for use on Quick Performance rear ends.

While working on the rear coil overs, we opted to add a set of Viking Hybrid coil overs to the front to dial in the ride height and adjust our rebound and compression settings. Installing them is as simple as removing the spring and shock and replacing them with the Viking unit.

Wilwood was our go-to choice for the brake package. Out front, we went with the industry-standard Superlite SLC56 caliper paired with our 1978-1988 GM G-Body C5/C6 Front Brake Conversion Hubs, Bearing, Bracket Kit. In the rear, we opted for matching 4-piston Dynalites #14932-RD. To complement the rest of the chassis, we used a host of Proforged replacement steering components and our Bump Steer Adjustment Kit – Heavy Duty Race.

Wiring Made Easy

Now that the driveline has been installed, we contacted our friends at PSI Conversions for all of our wiring and related EFI conversion needs. Joe and the team had been racing for the last few years at our UMI Motorsports Park facility wth their shop truck Project Tan Lines.  The guys were excited about the project, and considering our close proximity, they wanted to make the trip out to help us wire and fire the car. We chatted about our needs and the components we had installed in the car, and PSI was able to get us handled regarding the fuel system and our computer and harness needs.

Before PSI made the trip out, we wanted to ensure the car was as complete as possible, so we installed the new Tanks Inc EFI fuel tank, in-tank pump, and corresponding plumbing before they arrived. The old tank was quickly dropped from the Cutlass and replaced with our EFI tank after being loaded with the Tanks Inc. supplied 255LPH pump. Plumbing was completed in 6AN hose, and we used a Corvette return regulator for the needed return line. Pro tip: we prefer the use of a locking-style fuel rail fitting for added peace of mind.

The PSI Conversion guys showed up in force with four guys and their in-house tuner. We split into a couple of teams to tackle the PSI Harness, Dakota Digital Gauges, and the UMI guys on finishing the installation of the Wizard Radiator and Spal fans.

We opted to install a plate on the bottom of the dash behind the glovebox to house the PCM and TCM so our harness installation would start from this location. A 2″ hole was drilled through the firewall, and the harness was fed into the engine bay. Connections are a snap since PSI builds the harness with the correct length and connector for all of your factory engine and transmission connections. Power is supplied to the harness via a connection to the starter power lug. Now that the harness was buttoned up, we plugged in and mounted the PCM and TCM supplied by PSI Conversions.

While one team worked on the harness installation, the other PSI guys connected the Dakota Digital-supplied new dash display and control box. Most of the pertinent gauge signals are easily pulled from an OBD2 connection, but you will have a couple of wires installed directly into the control box, like the fuel level sensor. A few factory connections will be made to get your turn signals and dimming functions working with the new cluster.

Updating the Cooling System 

The UMI guys tackled the installation of the Wizard Cooling Radiator assembly into our Olds. Wizard provided us with their 26.25″ LS Swap Radiator and a twin Spal brushless fan assembly. We currently run Wizard Radiators in our in-house race cars and most of our street cars, so we know they will give us peace of mind for our Cutlass build. One hiccup I have seen folks run into is what radiator hose to run. After some trial and error, we developed a good combination of off-the-shelf hoses with some slight modifications (part numbers listed below). The Spal fans had the proper harness to fire them up when the temperature reached 190 degrees. Wiring these in requires using a Maxi Fuse in conjunction with the supplied wiring.

With all that work finalized, we are ready to fire the Cutlass. The crew made a last once over for any issues, and we changed the car for leaks; all was in order, so we turned the key. We have ignition! After months of work, we have a moving car once again.

The home stretch

With the milestone of a running car reached, we turned our attention to finishing the countless odds and ends needed to make this project complete. Double-checking connections and adding an intake and catch can setup to the cutlass were next in line. For the intake, I reached out to MP Intakes on Instagram, and Mike custom-made our intake to our specifications, finished it in a black powder coat, and turned it around to us in no time flat. The fit and finish are really nice touches to finalize the engine bay. For the PCV setup, we teamed up with Might Mouse Solutions for a Gen 6 catch can to keep the blow-by in check.

We were now getting into crunch time, so the Cutlass was loaded into our trailer and hauled out to Pittsburgh, where Mike at FineTuned dialed in the tune and gave us the street manners we were after. Cannonballing back to UMI Motorsport Park, we tested and dialed in the suspension setup. Immediately back into the rig, heading down to LS Fest East to be used as our hotel commuter car, where the Olds did not disappoint.

Pace Engine in the Cutlass

Our New Oldsmobile 

With some miles now put on the odometer of our Olds, we were able to reflect on how far this car has come.  From a pristine yet underpowered cruiser transformed into a modern hot rod with enough power on tap to put a smile on your face.  Driving the Cutlass brings back a sense of nostalgia while giving you the confidence to take it anywhere.  Our expectations were to make a car that was a joy to drive, turn heads at trade shows, and have some fun on the weekend cruises, and we checked all of those boxes and more.

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