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Hi everyone! I am doing quite the swap on my pickup and I was looking for pointers. First things first... the rig is a 1980 GMC high sierra 2500. four wheel drive corporate 14 in the rear and gm 10 bolt up front, 4.10 gears, lockright locker in the rear, th400 trans, 205 t-case and small block 400 mill. I managed to get a hold of a 1970 Eldorado with a cadillac 500 in it and a BOPC th400 trans from a friend. Rebuilt the cad trans and engine already, and also the transfer case out of the pickup is rebuilt. I have the new trans installed in the rig already and new motor mount plates put in. I bought some new motor mounts that go to a rear wheel drive cadillac and put on the engine. the problem i am running into is getting the engine to fit in the pickup. the truck is stock height and everything and i want it to stay that way. I was wondering if anybody else on here has done this kind of swap and if I could get some info from someone who has done it before?

Thanks!
 

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Eldorados have a rear sump pan. Devilles had a sort of mid sump. Max Torque Specialties (I think thats the name) and another outfit in Albuquerque sell lots of conversion stuff. Most go into Monte Carlos so a pick up should be easy. I have one in a rock crawler and it is super smooth and lots of torque. Google Cad 500 and most of the conversion companys come up. Both companys have different oil pans and oil pumps with different oil filter angles as well.
 

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you can use bbc headers, just cut off the flange and weld on the caddy flange. should be easily doable.

425 caddys from 77 and up had a rear sump pan, make sure you get the pickup that came with it.

saw a guy with a 500 caddy with an edelbrock intake, headers, and a quadrajet carb dominate 3 classes at the mud races with 3.73 gears and 38.5 boggers. properly tuned, they do really well.

watch the rocker arms, over 5000 rpm and they wont like you. it will probably get decent mileage if you have high enough gearing to keep it in its sweet spot, about 2000-2500 rpm at cruise speed.

you should be able to put mounts on it and keep it in the stock location, just adapt the motor mounts to the flat plate under the stock chevy mount.
 

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Discussion Starter #6
The Eldorados all had rear sump pans so clearance is not an issue. I have actually spoke with the mts guys and bought some stuff off their website for the engine. The cadillac motor mounts are about 3 1/2 inches farther forward than the original pads for the sbc mounts. I built some extensions that bolt to the pads and effectivly move the pads far enough forward to mount the cad motor mounts. The extensions ar 3/8ths plate so that should hold it pretty good. My dad and I attempted to put the engine in the engine bay to drill the holes in the plate for the mount studs, but the brake booster is in the way. I plan on removing the brake booster tonight and re-stabbing the engine. I will also try and take some pictures tonight and post them so you guys can get a better idea of what I am doing. Thanks for all the quick replies. Has anyone ever put one of these in they're daily drivers?
 

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Another pan that will fit is from a 368. In my opinion it is better than the El Dorado pan. The El Dorado pans are rumored to split because it is a single stamped piece. It is also "divited" on the passenger side for better driveshaft clearance there.

I wish I had a better picture of one but:
 

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I had to grind a 1/4" off of the passenger side frame to clear the exhaust manifold and modify the firewall just forward of your throttle foot to clear the driver's side cylinder head. I used a HydroBoost and still only had an inch of clearance to the valve cover.
This is all in a 1970 C30.
 

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You will love the caddy power in that thing. I have done the swap on 2 differnt blazers, an 84 and 86. Also in a 71 c20 and just recently into an 86 442 olds. The 84 blazer had a 3" body lift on it when I bought it and the motor went in very easily, the 86 had a 6 inch suspension lift with no body, it was a chore. Pull the front clip, it will make life much easier. You have to remove the brake booster, set the motor down in and you will see two places on the firewall that will need work. There is a double plate around the booster that sticks out about an inch. I cut slots in it and used a hammer to beat it flat. I was using a chevy th400/205 bolted in the stock location with an adapter plate to mate the two, you may have to adjust where you bolt the trans in the frame.
Is the motor really a 70? Seems everyone selling these things say they are but most of the time thats not true. I have had to tell guys numerous times they were full of crap when buying these things. The 70 is the only year of the "high compression 500" rated at 10:1 which is actually closer to 9.5:1 all later years are 8.5:1 and in reality closer to 8.1. They say this because this motor was rated at much higher hp than the laters, really nothing to it due to the way the horsepower ratings changed. All the motors are within 20-30 hp of each other, not 100s like people seem to think. Pull a valve cover and look at the casting number last 3 #s in 70-73 will be either be 250, 902 or 950 and small chamber heads. If its 493 or 552 then its a much more common 74-76 large chambers. If it turns out to be a later 500 then the heater outlet will be on the passenger rear head, which is a real PITA and almost always causes problems. If it is a 70 it will have the heater outlet under the T-stat housing up front. You can plug the rear head on later 500s, drill and tap under the t state and install a nipple due to not have room at the rear.
Also if it really is an eldo motor it will have a rear sump, if its a front sump then it came out of a rwd caddy. A 425 pan is a mid sump and will work in the truck chassis but you have to ping the pan at the second and third rods at the front. The rod bolts hit slightly and cause a knock. I used this pan in my 71 and actually pulled it because I thought I messed something up and happened to see the paint flaking where it was hitting. If you plan on even locking the hubs in get rid of the 10 bolt, these motors make as much or more low end torque than most diesels and will destroy that thing the first trip out. I learned the hard way. Sorry for the long post and hope this helps.


Robbie
 

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Also almost forgot, alot of times there is a clearance issue with the stock oil pump/ filter at the core support. You can use a 77 and up 425 pump which clocks the filter in towards the balancer instead of out towards the core support.

Robbie
 

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Great info guys!

I will add, I installed a 472 in a friends '85 3/4 ton 4wd several years ago and we were on a very limited time frame as he drove the truck from Ft. Collins, Colorado to my shop in NE Oklahoma during a week long hunting trip and had to drive the truck back to Ft. Collins the next weekend. I just cut the engine cross-member from the Caddy donor prior to him coming down and after removing his engine and frame mounts I just cut the cross-member to fit into his frame, lowered the engine, tranny, transfer back in, bolted them to the (new) factory engine mounts on the Caddy cross-member, located everything as it should be and welded the Caddy cross-member in and added gussets. It was really easy.
 

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Discussion Starter #16
Yellowroket71,

Thank you for the great info! A long post is no big deal when you get that much info in there. And it is for sure a 1970 engine. The engine was dwelling under the hood of a 1970 eldorado when I aquired it. 500 bucks brought it home. Drove it up on the trailer actually. Once home commenced to destroying the front tires.... I knew the 500 cad engine was the right choice for the swap when i saw that it was able to smoke the tires on that old cad at 40 mph! I actually got it in tonight but haven't figured out how to put pictures on here, but when i do I will get them on as soon as possible. One question though, what kind of motor mounts did everyone use in their swap? I just used 74 deville mounts and it seems to sit just a tad high in the front.
 

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All of the rwd caddy mounts are the same. I ran into the same problem of the motor sitting high in the front on the 86, well the 84 did too but with the body lift it didnt bother me. This is the problem with using just a flat plate off the cross member.I took some thick 3x3 angle and put them back to back (picture making a T) bolted the engine to one piece of the angle and set it down in. You can tack the back piece of angle to the front and top of the engine cross member, then set the motor down, up or side to side where you need it and weld it to the other piece of angle. I then fully welded it in and drilled two 1/2" holes through both sides and plug welded the two pieces to the x-member. Doing it this way will allow you to set it however far down you want to go with given oil pan clearance.

If you use the angle or flat plate you need to run a gusset in the center under the mount. The caddy in my 442 has ported big valve heads with a somewhat mild cam and was bending 3/8" plate until I put a gusset under it.

Also if this engine is still stock you should really open it up and check it out.They came stock with a plastic tooth cam gear that uses thin mesh riveted together as a chain. They will jump time pretty easily and usually take some valves with them. The valve springs are so weak most of the time the valves will float at or below 4500 rpms, you can get some cheap springs kits for not much money. MTS (Maximun Torque Specialties) is the best place to get parts, Marty and JW are awesome guys. They are actually filming an episode for Horsepower TV on spike doing a caddy build as we speak.

Robbie
 

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i put a 500 in my 85 gmc 2500, only had to fab a flat plate off the stock mounts that picked up on the caddy mounts, added the bop adapter plate, and modified the front crossmember. the pan clearance wasn't an issue for me cause i had enough lift. oh ya, i had to bash in the fire wall a little for clearance on the valve covers. Awsome motors, good luck
 

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i put a 500 in my 85 gmc 2500, only had to fab a flat plate off the stock mounts that picked up on the caddy mounts, added the bop adapter plate, and modified the front crossmember. the pan clearance wasn't an issue for me cause i had enough lift. oh ya, i had to bash in the fire wall a little for clearance on the valve covers. Awsome motors, good luck
few years late there.... ah he's a newb
 
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