CadVetteStang
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82 Eldorado 500 engine swap details
82 Eldorado “The Cadinatorâ€
Brief History of the Car
I bought the 82 Eldorado to fulfill the need for immediate transportation while my 72Mustang was down for major repairs. I got a good deal on the Caddy because it needed a front cap. My son and I did the repair and I sent it to get a cheap paint job. It had a good 4100 engine with low miles. I drove it 52,000 miles that year getting just over 25 MPG as a traveling salesman. I have heard some reports of the 4100 powered Eldos getting up to 32 MPG, but I average 80 MPG on the interstate with this shoebox shaped car and Arkansas has a lot of hills in the rural areas as well. With 4 wheel independent suspension, this car already handled better than my 1972 Mustang and with 4 wheel disc breaks it stopped quicker as well. When I upgraded to the thicker sway bars from an 85 Eldorado touring coupe, I was driving a car that handled almost as good as the 70 Elorado. The 82’s springs were too soft in back, and the torsion bars were so weak in the front, it was more like flying a hover craft than driving a car; I knew there was room for improvement. I swapped the rear springs with used ones from a 70 Malibu Station wagon and the car started cornering flat like a late model Camaro. I was still doing research for the front torsion bars hoping to find something stiffer than the 79-85 touring bars when trouble began to happen.
The 500 Swap Planning
At some point, the transmission quit shifting into fourth gear, but the engine was so quiet and the shifts so smooth, I did not notice anything but a dramatic drop in gas mileage. Not realizing I was buzzing the motor hundreds of miles a day with the 3.15 front gear ratio, the 4100 soon began to suffer from the notorious upper end knock that they were known for. Since I had already discovered that with several more upgrades, this 3680 lb. car had the potential to handle in a Corvette-like manor and was in the same weight class, I was already thinking about doing a big block Caddy swap. Since the big block Caddy engine only weighs 35 lbs. heavier than the 350 Chevy, cranks out more power then the 454 Chevy, I had the potential of bettering the power to weight ratio of a C5 Corvette Z06. Not to mention that with fuel injection, those engines can be built to get gas mileage close to that of a GM V-6 of the mid- 90s, I could still drive hundreds of miles a day with no real drop in gas mileage. The 82 Eldorado used a TBI injection system like the one used in the Chevy 454 SS truck, so a throttle body and sensor swap would allow the use of the existing OBD 2 engine management system.
The Swap Begins
I upgraded the radiator to a Chevy truck 4 row, put in a salvage yard Caddy 500 and added an exhaust that consisted of dual 2.5†header pipes that joined into a single 4†pipe in the tunnel, then back into dual 2.5†pipes and turbo mufflers.
My research showed that this was going to pretty much be a DIY bolt in swap, IF all was planned right and attention was paid to the details. The 80-81 Eldorado had a 368 engine available which is also in the 425/472/500 family. I found one of those and pulled all of its brackets, pulleys, the fan shroud, computer distributor, and most importantly- its oil pan.
If installing this engine onto the TH325 or TH 325 – 4L transmission like I did, be sure to get the flex plate as it has the small torque converter bolt pattern. The engine is a direct bolt up to the tranny at the back, but one bracket needs to be made to connect the front of the transmission to the lower front of the engine. That was easy and I also fabbed it to help hold one end the torque strap that I made from aircraft cable which secured the engine to the frame. The 500 can really rock back and forth on those soft Caddy mounts.
If you plan to swap in the stronger TH425, you will need to fabricate tranny mount locations and create some clearance in the lower firewall area with a hammer or some cutting and welding (its not much firewall bending that is needed, so if it’s not a show car, the 4 lb. sledge will do the job; and the average person looking under the hood will not see the modification.)
The first engine I pulled from a salvage yard to put into the Eldo was a 500. I wanted to retain my overdrive, lockup converter, and full dash instrument functions including the MPG sentinel, so I pulled off all of the sensors from the 4100 engine that came out and adapted them to the engine that was going into the car. I had a TBI adaptor made (not knowing at the time they were available at the local speed shop – LOL). And we welded a sensor fitting into the intake manifold for the MAP sensor. I wanted to find a 670 CFM TBI from a 454 SS truck, but one was not available at that time. Temporarily I used a 500 CFM TBI from a 350 and installed the sensors of the 4100’s TBI because of different resistance values. The only wiring harness modification I had to do was in hooking up the 368’s distributor and I had to make the wire longer and change the connector.
When the 500 engine went in, it did so in a way that the computer could not tell the difference between it and the 250 that came out. Both engines were rated at the same compression ratio and both had stock cams. The 81- 85 Eldorado does not have a knock sensor and so the computer is easy to fool.
The overall job was time consuming, but was less difficult than I thought it would be. When I finally got the swap finished and started the engine, I discovered it had bearing problems… I could not afford any engine work and did not have time to find a mechanic for the overhaul. I had a warranty on that engine, but the salvage yard did not have another good running Cadillac 500 at that time. Because of my rushed schedule, I pulled a 472 from a 1972 Lemo rated at 535 lbs. of toque @ 3000 RPMs after hearing that it had been rebuilt by the former owner. The engine was painted in a way that suggested is had been apart.
I did the swap over again (this time it went much faster) and began driving the car to see if I could get the transmission to start shifting into over drive. I was also still looking for a taller front diff to swap in. I found that even without 4th gear and with the low 3.15 front diff, I was getting 20 MPG at 50 MPH. Better gears would have yielded the same MPG results at my 80 MPH normal driving average, and even better results at the 70 MPH speed.
However, the engine began knocking 212 miles after I had installed it. Discouraged, out of time and not looking forward to a third swap, I parked the car and bought another daily driver. It sat in a field for five years next to my 70 Eldorado.
I was recently doing a budget for the restoration and completion of this car and had hoped to race it in an autocross before the fall of 2009. My plans got accelerated when I discovered that my wife had saved $500 towards my resurrection of this project. I called my friend who was storing it and my 70 Eldorado to make plans to get one or both cars, and that’s when I found out it had been stolen and hauled to the crusher by his cousins. I’m currently finding out my legal options in this matter.
I may rebuild another 79 – 85 Eldorado as a pro touring car and if so, I will better document the engine swap and suspension buildup. Based on what I discovered during trial and error in the first swap and suspension buildup, I have no doubt that this car can be tuned to break the 1 G lateral acceleration barrier and can go from 0 – 60 in the 4 second range. It has the potential to out perform all but the best handling setups in the C1 – C3 Corvettes and non-Z06 C5 and C6 Corvettes, however, how it might compare to the C4 Vettes in the autocross remains to be seen. My hopes are up, but the FWD configuration, the front to rear weight balance and the longer wheel base are design handicaps that will hard to overcome. I do expect it to be able to run with the Vettes in road racing courses at speeds up to 120 MPH, after that, however, bad aerodynamics and a lack of down force will put a cap on its performance handling characteristics. It will still be one BAD Eldorado, however, that should get attention and respect from every driving event it is entered in.
Cody G. Carson
82 Eldorado “The Cadinatorâ€
Brief History of the Car
I bought the 82 Eldorado to fulfill the need for immediate transportation while my 72Mustang was down for major repairs. I got a good deal on the Caddy because it needed a front cap. My son and I did the repair and I sent it to get a cheap paint job. It had a good 4100 engine with low miles. I drove it 52,000 miles that year getting just over 25 MPG as a traveling salesman. I have heard some reports of the 4100 powered Eldos getting up to 32 MPG, but I average 80 MPG on the interstate with this shoebox shaped car and Arkansas has a lot of hills in the rural areas as well. With 4 wheel independent suspension, this car already handled better than my 1972 Mustang and with 4 wheel disc breaks it stopped quicker as well. When I upgraded to the thicker sway bars from an 85 Eldorado touring coupe, I was driving a car that handled almost as good as the 70 Elorado. The 82’s springs were too soft in back, and the torsion bars were so weak in the front, it was more like flying a hover craft than driving a car; I knew there was room for improvement. I swapped the rear springs with used ones from a 70 Malibu Station wagon and the car started cornering flat like a late model Camaro. I was still doing research for the front torsion bars hoping to find something stiffer than the 79-85 touring bars when trouble began to happen.
The 500 Swap Planning
At some point, the transmission quit shifting into fourth gear, but the engine was so quiet and the shifts so smooth, I did not notice anything but a dramatic drop in gas mileage. Not realizing I was buzzing the motor hundreds of miles a day with the 3.15 front gear ratio, the 4100 soon began to suffer from the notorious upper end knock that they were known for. Since I had already discovered that with several more upgrades, this 3680 lb. car had the potential to handle in a Corvette-like manor and was in the same weight class, I was already thinking about doing a big block Caddy swap. Since the big block Caddy engine only weighs 35 lbs. heavier than the 350 Chevy, cranks out more power then the 454 Chevy, I had the potential of bettering the power to weight ratio of a C5 Corvette Z06. Not to mention that with fuel injection, those engines can be built to get gas mileage close to that of a GM V-6 of the mid- 90s, I could still drive hundreds of miles a day with no real drop in gas mileage. The 82 Eldorado used a TBI injection system like the one used in the Chevy 454 SS truck, so a throttle body and sensor swap would allow the use of the existing OBD 2 engine management system.
The Swap Begins
I upgraded the radiator to a Chevy truck 4 row, put in a salvage yard Caddy 500 and added an exhaust that consisted of dual 2.5†header pipes that joined into a single 4†pipe in the tunnel, then back into dual 2.5†pipes and turbo mufflers.
My research showed that this was going to pretty much be a DIY bolt in swap, IF all was planned right and attention was paid to the details. The 80-81 Eldorado had a 368 engine available which is also in the 425/472/500 family. I found one of those and pulled all of its brackets, pulleys, the fan shroud, computer distributor, and most importantly- its oil pan.
If installing this engine onto the TH325 or TH 325 – 4L transmission like I did, be sure to get the flex plate as it has the small torque converter bolt pattern. The engine is a direct bolt up to the tranny at the back, but one bracket needs to be made to connect the front of the transmission to the lower front of the engine. That was easy and I also fabbed it to help hold one end the torque strap that I made from aircraft cable which secured the engine to the frame. The 500 can really rock back and forth on those soft Caddy mounts.
If you plan to swap in the stronger TH425, you will need to fabricate tranny mount locations and create some clearance in the lower firewall area with a hammer or some cutting and welding (its not much firewall bending that is needed, so if it’s not a show car, the 4 lb. sledge will do the job; and the average person looking under the hood will not see the modification.)
The first engine I pulled from a salvage yard to put into the Eldo was a 500. I wanted to retain my overdrive, lockup converter, and full dash instrument functions including the MPG sentinel, so I pulled off all of the sensors from the 4100 engine that came out and adapted them to the engine that was going into the car. I had a TBI adaptor made (not knowing at the time they were available at the local speed shop – LOL). And we welded a sensor fitting into the intake manifold for the MAP sensor. I wanted to find a 670 CFM TBI from a 454 SS truck, but one was not available at that time. Temporarily I used a 500 CFM TBI from a 350 and installed the sensors of the 4100’s TBI because of different resistance values. The only wiring harness modification I had to do was in hooking up the 368’s distributor and I had to make the wire longer and change the connector.
When the 500 engine went in, it did so in a way that the computer could not tell the difference between it and the 250 that came out. Both engines were rated at the same compression ratio and both had stock cams. The 81- 85 Eldorado does not have a knock sensor and so the computer is easy to fool.
The overall job was time consuming, but was less difficult than I thought it would be. When I finally got the swap finished and started the engine, I discovered it had bearing problems… I could not afford any engine work and did not have time to find a mechanic for the overhaul. I had a warranty on that engine, but the salvage yard did not have another good running Cadillac 500 at that time. Because of my rushed schedule, I pulled a 472 from a 1972 Lemo rated at 535 lbs. of toque @ 3000 RPMs after hearing that it had been rebuilt by the former owner. The engine was painted in a way that suggested is had been apart.
I did the swap over again (this time it went much faster) and began driving the car to see if I could get the transmission to start shifting into over drive. I was also still looking for a taller front diff to swap in. I found that even without 4th gear and with the low 3.15 front diff, I was getting 20 MPG at 50 MPH. Better gears would have yielded the same MPG results at my 80 MPH normal driving average, and even better results at the 70 MPH speed.
However, the engine began knocking 212 miles after I had installed it. Discouraged, out of time and not looking forward to a third swap, I parked the car and bought another daily driver. It sat in a field for five years next to my 70 Eldorado.
I was recently doing a budget for the restoration and completion of this car and had hoped to race it in an autocross before the fall of 2009. My plans got accelerated when I discovered that my wife had saved $500 towards my resurrection of this project. I called my friend who was storing it and my 70 Eldorado to make plans to get one or both cars, and that’s when I found out it had been stolen and hauled to the crusher by his cousins. I’m currently finding out my legal options in this matter.
I may rebuild another 79 – 85 Eldorado as a pro touring car and if so, I will better document the engine swap and suspension buildup. Based on what I discovered during trial and error in the first swap and suspension buildup, I have no doubt that this car can be tuned to break the 1 G lateral acceleration barrier and can go from 0 – 60 in the 4 second range. It has the potential to out perform all but the best handling setups in the C1 – C3 Corvettes and non-Z06 C5 and C6 Corvettes, however, how it might compare to the C4 Vettes in the autocross remains to be seen. My hopes are up, but the FWD configuration, the front to rear weight balance and the longer wheel base are design handicaps that will hard to overcome. I do expect it to be able to run with the Vettes in road racing courses at speeds up to 120 MPH, after that, however, bad aerodynamics and a lack of down force will put a cap on its performance handling characteristics. It will still be one BAD Eldorado, however, that should get attention and respect from every driving event it is entered in.
Cody G. Carson
