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72big Caddy into '79-'85 Eldo/Seville

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  • Cody Carson
    Aug 2, 2002
    • 0 Attachment

      Putting a Big Cad into my "82 Eldo while keeping the stock computer and using a stock style fuel injection system was a big challenge, but was well worth it. The following is what I remember about the swap-some details have been forgotten, but if anyone attempts this swap, feel free to ask me any questions, and it should bring back a memory of how I dealt with the problem. What I have written is not organized as well as I would like, but here goes: The 368 heads, intake, and exhaust manifold are different, but most all brackets and pulleys can be used. I used a 472/500 Eldo exhaust manifold on the driver's side (tight bend on the header pipe-only good muffler shop can make that bend, but it can be done-the steering shaft is in the way). I used a RWD manifold on the passenger side-a welding school re-clocked the opening so that the bolts would clear the AC box and I made some extra room by using a hammer to flatten the edge of the frame rail where the header pipe bolts up. I don't trust the exhaust manifold weld, so when I pull the engine again to do a rebuild, I am going to cut the frame enough to put a non-modified RWD manifold there, and have extra metal welded to the frame to restore its strength. The 45 degree oil pump can be used (info circulating about how only a 90 degree one will fit is wrong). I ground 1/4" off of the upper idler arm mounting nut to give some better clearance for the install, and shortened the bolt accordingly. That will make it easier to change the idler arm when it goes bad, and I might now have enough room to get the oil pump on and off w/out unbolting and prying the engine.(Speaking of which, the '82's cross member bolt holes do not line up with the '80 368 mount. Take note of where the holes are in the '80 since you will have to drill out the new hole pattern. I put slits-not holes- in mine so that I could unbolt and pry the engine over a little if I needed more room to work on it;that also helps with breaking it loose from the trans and twisting it during the install. You can paint alignment marks on the cross member so that the engine gets bolted down straight, and if you use toothed washers, you won't have to worry about the engine shifting in the slots...I think the '80 uses slotted holes anyway now that I think of it. The "80 368 fan shroud should be used. I have used both a fan clutch and a solid fan-the solid fan with spacer is almost impossible to bolt up due to the tight clearance at the radiator, and I scratched up my radiator pretty bad attempting it-a thermal fan clutch is worth a 3 1/2 mpg improvement anyway-and is MUCH easier to install. You'll have to do the fan and shroud at the same time as with other cars of tight radiator clearance. If you use the same style AC compressor that came with the '80-'85 Eldo, then you will have to weld a stud to the intake to get the stock AC bracket to bolt down in back, and you will need to build a custom upper radiator hose connector since it won't interchange from the 368. You will also need to come up with a custom upper hose.  The next time mine comes off, I'm going back to the axial style compressor that came on the earlier 472/500 cars, so I can use the stock hose connector and a stock '70's Eldo upper radiator hose. It will make it MUCH easier, and will look factory. Some of the brackets/accessories might have to me changed for belt alignment, but if you use all of the hoses/pulleys from a '70's car it should not matter. I used as much 368 stuff as possible because I wanted to keep the AIR pump and all computer accessories functional. I use a 4 core truck radiator (minor hammer fit was needed to the core support on one end, but the metal is very soft and it shapes easily). If you want to keep the AIR diverter valve, forget the stock bracket that bolts to the manifold, re-mount that bracket from the intake, or on the inner fender well. I can't remember what the problem was, but I ended up using a wire tie and strapping the diverter valve to the shock tower support. On the driver's side, the challenge is the shifter bracket that bolts to the 368 manifold. Rather than deal with it, I used the cable shift mount and column shift cable from a '79-'85 Tornado/Riviera. The shift lever will be needed to do a bolt on swap and for that you will have to get the trans pan off to replace it, or with the engine out you may be able to chisel off the tack weld and tack the new shift lever on the shaft in its place. I went one step further in customizing and put in a console floor shifter from a '90 eldo. I still need to modify the neutral safety switch that is in the column to finish this modification because the column shifter tells the computer when the car is in drive-(no worry here if you are not using the computer). The 90 Eldo shifter has a neutral safety switch built on the shifter, so finishing that part of the mod won't be a problem. ( I have not seen a trouble code come up yet- but I want it to be right)

        I use the stock computer system to run the car. I accomplished this by mounting a 400 CFM TBI from a '92 Seville on a flat metal plate that is bolted to an aluminum Quadra jet to square bore carb adapter on the stock intake manifold. I used the 400 cfm TBI due to not being able to find a used 670 TBI from a late '80's 454 truck, but that is what the car actually needs and I am in the process of looking for a used one. (on the 454's TBI, the TPS will have to be changed out for the one on the 4100's TBI and the Idle control motor installed-easy enough)  I took all of the sensors off the 4100 and installed them on the 472. The MAT sensor was mounted by drilling a hole in one of the intake runners and welding on a 3/4" pipe fitting. The metal temp sender (the one wire sensor mounted on the front and back of the head) came from the older 472 since it threaded differently in mine if I remember. I got rid of the pulley driven vacuum pump by making installing a vacuum tree at the back of the carb adaptor and using a 425/472/500 power steering pump. I think I had to change the pulley

         For hood clearance, I used a low riser 14" chrome breather. I was able to use the 4100's breather spacer, and a 3" tall filter, but had to cut out one of the under hood support braces for breather clearance. Don't be surprised if you have to use a flat top breather-it will depend on the thickness of the carb gaskets you use. I have 1/4" hood clearance at the side of the breather, but not using a flat top breather, I have about 1/16" breather nut to hood clearance. I will eventually use a flat top breather so that I can use thicker carb gaskets. Clearance is not so tight when you use the 368 breather spacer since it is shorter, but I wanted the extra air speed to compensate somewhat for the low 400 cfm air flow. I also installed '86 turbo Thunderbird hood scoops that dump cold air in right in front of the breather. (The chrome shines from inside the scoops when the sun light is at the right angle and it hints of some serious horse power under the hood.)

       I do not have data on how well the trans will hold up with the power, but I do plan on using TH200-4R parts such as shift kits, ect on a trans rebuild later on. ( I had to park the car 215 miles after I started driving it do a knock in the engine-it was a salvage yard engine.) I did however change the fittings on the trans so that I now use 3/8 cooling lines to a big trans cooler-and I used a manual shift truck radiator w/o trans cooling lines so that I can get the radiator out quickly and easily for serious motor work.

       You will need the passenger side drive axle from the 368 car since the mounting locations are different on the 4100. Also, there is no bolt hole on the driver's side of the block to mount brace the block to the trans axle. I used the 4100 block-to-dif brace and a block-to-dif brace from a mid '70s Eldo (it bolts to the engine mount holes) I bolted them together with a custom adapter made by drilling two holes in a 3" long flat piece of metal to prevent having to drill and thread a hole in the side of the 472 block. 

        I will post more info at a later time, and I will eventually post some pictures of the car and of the HUGE exhaust system that is under it. ( the key to running the stock computer was that the '82 does not use a knock sensor) The '80 368 does, so the wiring is not a direct bolt on if your plans are to put a 368 into a later model-and they do use different computers al together. I do use the 368 distributor and did not need to modify it l-except that I took the plug hook up out of the 4100, and its control module and made the wires longer to reach the front of the engine. There is something about one of those wires that I had to deal with, but it was minor, and I can't remember what it was-oh, yes, the base timing lead plug-no problem.

      Important: the torque converter bolts don't line up. You will need to drill out new holes on the fly wheel if you use the 4 speed trans with the lock up converter. It lines up on a crease and some grinding will have to be done to get a flat surface, or you can order a heavy duty fly wheel from Al (recommended-if he sells one that fits this application). I found this out after the engine was in and had to do my mods while under the car with a drill and grinding wheel-no fun at all. The 368's fly wheel: the number of teeth/diameter is different than that of other cads. I can't remember if the starter interchanged, I know I had the 368 starter on hand incase, but I think I used the 4100 starter.

        I hope this helps and does not scare you away from the swap. It is involved, but I did it with no one giving advise. It was all "try it and see" attempts, but the prize was well worth the race. I use Reccaro style bucket seats on the stock six way power mounts. I have a 1and 5/16" front sway bar (thicker than on a Corvette) and a 1and 1/8" rear sway bar-(touring suspension). I am proud of " St. Frankenstein, the Eldomonster" that was put together from many parts of dead cars- yet lives again. When it fires up, the loud, low rumbling exhaust note from such a tame looking car not only turns heads, but mouths drop open and people gesture for me to raise the hood as they walk towards the car in disbelief.

      Cody 



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