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G-Body swap guide posted by Richard Durost on MTS board

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  • cody_g_carson
    Posted by Richard Durost on 9/3/2002, 2:46 pm I haven t done this swap yet, but the information has been validated by somebody who has. ... GM
    Message 1 of 1 , Sep 3, 2002
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      Posted by Richard Durost on 9/3/2002, 2:46 pm

      I haven't done this swap yet, but the information has been validated
      by somebody who has.

      GM G-body Cadillac Engine Swap Guide

      ('78-'88 Monte Carlo, Malibu, El Camino, Grand Prix, Le Mans,
      Cutlass, Regal, etc.)

      You can use a Cadillac radiator. Use the radiator saddles and top
      brackets from the Cadillac. The Cadillac radiator has a heater hose
      fitting at the top of the passenger-side tank. Strap the hose to the
      battery tray to keep it away from the fan.

      If your Cad engine has a heater hose fitting on the rear of the
      passenger-side head, remove and/or plug it and put a new fitting in
      the boss on the outside, below the thermostat housing. Pre-'71
      engines came with this configuration from the factory. This will give
      you more firewall clearance.

      In order to fit the Cad radiator in the G-body chassis, you'll need
      to trim the core supports to clear the tanks. Reinforce the bottom of
      the support with 3/16" x 1 1/2" flat stock after trimming it. Make
      sure the radiator only makes contact with rubber all the way around.

      A pair of Chevy Citation electric fans will work. If you use an
      engine-mounted fan, use a shroud modified for clearance.

      A stock Cadillac upper hose will work, but you may have to use a
      universal ribbed hose on the bottom. Make sure the idler arm bolts
      don't rub against the lower hose. You can cut the bolts flush with
      the nuts and grind them smooth to make additional clearance.

      If you use factory iron exhaust manifolds, on the passenger side
      you'll have to eliminate the heat riser valve, if any, and weld the
      header pipe to the exhaust flange at an angle in order to clear the
      frame. Maintain a minimum 3/8" clearance. On the driver's side,
      you'll need to grind the bottom outside edge of the flange to within
      1/8" of the bottom stud in order to clear the crossmember.

      The most common rear end ratios are 2.41 or 2.73:1. The stock rear
      will survive behind a mild motor if you stick with street tires and
      it's in decent shape to begin with.

      You can use the Cadillac transmission yoke on the G-body drive shaft.
      The U-joint bearing sizes are the same, but you'll have to cut out
      the ball that's there to center the Cadillac's constant-velocity
      joint assembly. Shorten the driveshaft to 42 15/16" (measure your
      installation to be absolutely sure), measured between the U-joint
      centerlines, to accommodate the Cadillac long-shaft transmission. You
      can use a short-shaft transmission, but it provides no functional
      advantage, and the driveshaft will have to be shortened anyway. If
      the stock driveshaft is too small for your application, you can start
      with the 2 3/4" unit from a '78-'82 Camaro or Firebird.

      Use the Cadillac power steering pump. If you're eliminating the air
      conditioning, you can run a belt straight from the pump to the crank.
      A Gates 11A1195 should be close. The stock Cadillac power steering
      hoses will usually work. If your steering box has metric fittings,
      you can use 3" sections of the hard lines from the steering box as
      adapters. The low-pressure return hose can be clamped to the stub of
      tubing from the box. Trim the fitting off the high-pressure hose and
      join it to the cut line from the box with a 3/8" compression fitting.

      To delete the AIR pump, if you can't locate a pulley set from a '70
      engine, use a complete pulley set from a '77-'80 425 engine. These
      used no AIR pump either. You can seal the air tube fittings on the
      front of the heads with cup plugs, or tap them for pipe plugs that
      you KNOW won't blow out.

      Air conditioning can be retained with minor modifications to the
      heater/AC box, with reduced access to the #7 spark plug. You'll have
      to cut a clearance well in the outside of the housing to clear the
      valve cover. Make sure you don't cut into the A/C gear inside. This
      is better done with the top half of the housing removed. Heater-only
      cars will require a smaller clearance hole in the housing. Thin sheet
      aluminum or fiberglass can be used to create a clearance pocket in
      the housing, making sure that you don't run into the squirrel cage

      Maintain a half inch clearance between the driver's side exhaust
      manifold and the steering column. You can shift over the lower end of
      the column by redrilling the holes that attach the lower column
      bracket to the firewall inside the car. If your steering coupling has
      a grease fitting, you'll need to cut or remove it, or replace the
      coupling with one without the fitting.

      If you want to run headers, your best bet is to start with big block
      Chevy shorty headers designed for a Chevelle (A body) and add Caddy
      flanges, available from MTS, Sanderson, or Headers by Ed. The
      Sanderson headers require tucking up the #1 cylinder tube and
      flattening the bottom of others on the passenger side, and extensive
      mods to the driver's side to clear the steering shaft. Other brands
      might provide better or worse clearance. An alternative here would be
      to use street-rod-technology U-joints and a swivel shaft support to
      move the shaft away from the engine. You will need a U-joint at the
      steering box, another close to where the steering shaft comes through
      the firewall, and a third in the middle next to the swiveling shaft
      support (looks like a heim joint) bracketed to the frame.

      Create additional exhaust clearance at the firewall by cutting flush
      the five sheetmetal screws protruding from the firewall next to the
      steering shaft. Flatten the passenger side of the lip around the
      steering shaft hole in the firewall and dimple the rest of the
      firewall in this area approximately 1/8".

      The column shift linkage won't fit. Remove it, being sure to fix the
      lever on the column in a "steering unlocked" position. Use a floor
      shifter instead.

      The Cadillac valve cover will reportedly clear a factory power

      You may need to cross the fuel line over from the passenger to the
      driver's side of the chassis. If so, use a 4' section of hard line
      attached to the existing line with a compression fitting. Route the
      line in the depression on the back of the crossmember, securing it
      with insulated clamps screwed to the frame. Maintain the hard line to
      within 8" of the pump, and add a section of rubber hose to allow for
      engine movement.

      Use a '68-'76 Eldorado oil pan, pickup tube, dipstick and dipstick
      tube. The rear-sump pan requires a different dipstick, and the
      dipstick tube needs to be inserted in the rear hole in the block.
      Knock out the ball bearing plugging this hole and transfer it to the
      front hole. After tapping the dipstick tube into its hole, gently
      bend the section of the tube inside the pan down toward the sump,
      keeping it away from moving parts. If you don't do this, the oil will
      read too low on the stick. The front oil pan drain plug should be cut
      out and replaced with a flat plate. This plug interferes with the
      crossmember and it will be inaccessible anyway. The notch in front of
      the sump that's used for front-drive half-shaft clearance prevents
      the oil in the small front sump from draining back, so either remove
      it or fabricate a drainback channel through it. Heli-arc or TIG
      welding is best, but in any case be careful to avoid cracking or
      warping from excess heat.

      The oil pump from the '77-'84 368 and 425 engines (Melling part #
      M58G) tucks the filter much closer to the block for clearance. You
      can use a remote filter setup, but the consensus is that this is to
      be avoided because it reduces flow and takes longer to build oil
      pressure on startup. You can also reportedly space the sway bar down
      2" and retain the 472/500 oil pump.

      You will need an aftermarket transmission crossmember, such as the
      one offered by MTS, or you can fabricate one. When placing the
      transmission mount, make sure the engine centerline is parallel with
      the vehicle centerline. The engine may end up shifted slightly to the
      passenger side of the vehicle depending on how you fabricate the
      engine mounts. That's fine as long as the trans mount is shifted a
      like amount to keep the engine's centerline parallel with the car's.
      If the engine is angled in the frame, you will get serious driveline
      vibration due to improper alignment of the U-joint(s).
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