500 Caddy/Monte Clip into El Camino

I'm in the beginning stages of a 500 Cadillac/83 El Camino swap. This is probably going to be a fairly long tem project but it should be fun. I have the major components gathered so the next step is going to be trial fitting and building mounts.

I had actually bought the El Camino as a parts car for another project and as I’ve had the 500 Cadillac engine sitting around waiting for right project and this seemed like a natural. The El Camino is rough but solid with the exception of one floor pan that needs a little work and the doors. While researching the interchangeability of doors I came across a picture of an El Camino that had a Monte Carlo front clip and doors swapped so doing that is now also going to part of the project.

I’m going to be building this as a daily driver capable of comfortably making cross country trips, get relatively decent gas mileage on pump gas and be very dependable.

. I managed to collect an SS dash with the 120 MPH speedo, tach and gauges. The 78 Monte Carlo I picked for the front end and doors will also be donating the non-computer wiring harnesses, power windows and locks, and 60/40 electric seats. I’ll also be adding aftermarket AC, and cruise control.

Of course I’m not the first to put a 500 in and G body, so some of the little things like exhaust and mounts have already been figured out.

This is the drive train that will be going in. The engine is a 1973 500 out an El Dorado the nice thing about having an Eldo engine is that it comes with the correct rear sump pan and pickup. It’s also an 8.5:1 compression motor that still makes 500 Foot Pounds of torque under 2500 RPM. I’m planning a stock rebuild on the engine with the exception of a little more cam and some stiffer springs to allow it to wind to 5000 RPM.

Fortunately I live in a area that doesn’t require emissions testing, otherwise this swap would not be feasible. I’ve changed the intake manifold to one from a 71 Caddy that does not have the EGR valve. I’m sticking with a stock intake rather than an Edelbrock for a couple of reasons; it’s very low lessening the air cleaner to hood problems, and while the Edelbrock does make a bit more power it move the torque curve up in the RPM range and I’m really looking for a lower RPM grunt motor.

I’ve also deleted the smog pump and piping. This can be a bit of a hassle as the original setup runs a belt from the crank to the smog pump and then a separate belt off the smog pump turns the water pump and fan. I was lucky enough to find a 70 Deville which had a one year only pulley setup that does not use a smog pump. And although it is close to the rear belt, I am also able to use stock HEI distributor from a later 425 Cadillac.

I'm also changing out the A6 AC compressor the engine came with for a Sanden 508.

From what I’ve read the stock drivers side Eldo exhaust manifold interferes with the steering so that has been changed out to one from a 71 RWD Caddy.

The transmission is a TH400 from a 69 455 powered Pontiac that I will be rebuilding prior to the final installation.

I really didn’t think the 7.5 rear end was going to be very happy for too long behind the engine and I debated for a while on what to do until I came across a 59 Ford SW 9” which happens to be the same width as the G Body rears. I rebuilt it and added a Posi with 2.75 Gears. The big Caddys in reasonably stock form don’t really like a lot of gear, so the 2.75s are what I’m initially going to try but I do have some other gear sets that are just a bit deeper if I need it. I bought the basic G body rear end brackets off of E Bay and spent a weekend getting everything welded up so that’s now ready to go under the El Camino. I’m changing the upper control arms out to a set of Lakewood adjustables so I can set pinion angle and will be boxing the lower arms and hopefully the stock rear sway bar I have will still fit.

Anyway that’s pretty much where I’m at right now with it.

Weight is not a major concern for this project and I’m going into realizing the truck will be considerably heavier when it’s done than it could be. While the Cady engines are relatively light compared to some other BB engines I came across a post on another forum where a completely dressed and ready to install 472/500 was actually weighed and compared to a similarly prepared SBC. The weight difference between the engines was actually closer to 100 pounds rather than the 50 pounds cited by a lot of places.

My understanding is that while the 368 aluminum intakes would save weight over the stock 472/500 intake it does not perform as well so it is also not being considered.

As far as the front clip/door change, I personally won’t know for sure until I actually try it. My understanding is that it is pretty much bolt on with the exception that that the front frame horns may need to be extended by about 3”. The problem comes from the body line at the bottom of the door. The line is about 4” from the bottom of the door on the Monte and 8” on the Camino. Most of the conversions I’ve seen look like the body line on the rear quarters are lowered to match the doors. Honestly it might be more involved than I’ve been led to believe making it unfeasible for me but I won’t know until I give it a shot.

I don’t know who owns this El Camino, but I do like the look (with the possible exception of the sun visor) so I’m going to give it a shot.