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THINGS MAY CHANGE but, for now, it is still impossible to find a moderately priced, accurate 1:32 scale locomotive. Fortunately, Lionel has an engine accurate enough to merit investing the time to correct its most glaring deficiencies, the "GP20".

Its predecessor, the Lionel GP7, is very accurate from the deck up. From the deck down, though, we must contend with its swiveling pilot and the 10-percent oversize trucks. The "GP20" is really nothing more than the GP7 with a low nose so, along with the GP7's problems, it also suffers from an incorrect louver pattern (among other things).

Even so, it is possible to make the GP20's overall appearance very realistic and to create a very satisfying model. Altogether I made seventeen changes. Some, such as correcting the swiveling pilots, are essential. Others, such as replacing grab irons and grills, are more subtle but contribute to the overall effect. Still others would require unobtainable parts (scale truck sideframes, diamond tread for the decking, and additional headlights) or too much time (correcting all the louvers or fixing the steps). I did remove the last two louvers on the battery boxes because they the most unique and obvious spotting feature of a GP7.

You may prefer to make only the more obvious changes and leave it at that. But I doubt you will want to go farther than I did because, at that point, you might as well scratchbuild a model or get a second job to pay for an all but perfect brass import.


Here we go.

Begin by removing the eight screws on the underside holding the body shell to the chassis. Label and disconnect the wires connecting the upper shell to the chassis circuit board. Cut off the shell's grab irons. Remove the number boards and classification lights. Remove all the handrails, but first square up all the stanchions. Note: Handle the stanchions very carefully. They are the Achilles heel of an otherwise rugged model. I broke a few and Lionel was very gracious about sending replacements at no charge.

Remove the low short hood (three screws hold it on). Slide off the cab. Remove the radiator and air intake inserts (the clear plastic rectangles) and the front and rear pilots (two screws hold each to the trucks). Then remove the couplers but avoid pulling apart the trucks unless you want to work on them. I had noticed a jerking motion when I test ran my units; it pretty much disappeared after I installed electrical m.u. cables and let the motors warm up with about 20 minutes of continuous running.

Remove the dummy air hoses. Label and disconnect the truck-to-chassis wiring and be sure to label the trucks, too. I marked each truck to indicate what end of the chassis it came from as well as the direction it faced.

Cut about 3/16-inch off the truck bolster spacers. The original truck pivot point should now be even with the top of the brake cylinders. That is very important because it lowers the body shell to the correct height above the rail.

Also remove the two screws securing the lead weight, the two securing the speaker backplate, and the four attaching the circuit board. Label and cut both ends of the speaker wire.


Cut the cylinder behind the speaker by about 11/16-inch. About 1/8-inch should remain. I used a Dremel rotary saw blade. Do not cut off the two posts where the backplate fastens. Then cut out the bulkhead between the speaker compartment and the air tanks (housing the on/off and volume control) but first remove all the electronic components. Slide the switch to the "on" position (the slider will be opposite the wires) and hold it with a dab of silicone adhesive. Be sparing so no silicone oozes into the switch housing. We will leave the switch unmounted. If you want to turn off the sound, just rotate the pot fully counter-clockwise.

Plug the vacant holes with silicone, then line both compartments with fiberglass. I had some R-19 house insulation, about 3 inches thick, so I pulled off some small pieces, lined all the surfaces, and made sure to leave air passages. The fiberglass will stay in position but I still used a few dabs of PolyZap for insurance.

We will reinstall the speaker during the final assembly, after painting everything.

Finally, clean out the debris and be certain, when you reinstall the speaker gasket, it has an airtight seal.


We will remove the pilots from the trucks, then attach them to the chassis at the correct height.

First cut off the rear tab even with the steps. Then add a 1/8-inch shim between the pilot and the chassis so the bottom of the pilot will clear the rail top by 4 scale inches, the same height as Kadee« coupler trip pins. I used Evergreen 1/8- by 3/16-inch styrene. Cut two pieces each 2 7/8 inches long with 45-degree miters on both ends, four pieces 2 15/16 inches long with blunt ends, and two pieces 15/16-inch long with the miter on one end.

The mitered pieces will form the front and sides and the two longest pieces will form the back (closest to the engine center) and middle support. This is a "working" seam so the alignment of the parts is important. Use the body shell to check the offset of the shims. You could also permanently mount the pilot and shim to the body but the construction would be more complicated and the coupler mounting structure weaker.


Cut off the molded plastic tabs representing lift rings. Putty and sand the resulting area of demolition as many times as necessary to leave the surfaces flat and smooth ( I used Squadron Green and 320 grit). When the putty has hardened, add the metal lift rings in the Parts List. They have a .040-inch threaded shaft. Drill holes with a #58 to #64 bit, whatever you have on hand, and twist on the rings; they are self-tapping.

Refer to the drawing for placing the rings; Southern Pacific used different locations than Lionel. Where the locations are the same, use the same points. I lined up my rings but, in practice, they faced every which way.


Lionel had the foresight to provide Kadee« 821 coupler pockets in the pilot but, if you modify the pilots as I have, the pockets will be at the wrong height. The 821 is preferable if your minimum radius is 8 feet. Many layouts use 4 foot radii (LGB 1600 curves) and, for those, you must use Kadee's 820 couplers. You must also modify the sides for extra swing as in Kadee's instructions.

Chisel out the coupler pocket so the 820 gearbox sits flush against the top of the inside of the coupler pocket. The coupler will be about 3/16-inch above its original position. It should protrude so a space of about 25/32-inch exists between the endplate and the inside of the pulling face of the coupler. That is standard for most diesels.

Enlarge all four gearbox mounting holes to 5/64-inch and add the couplers. The bolts will self-tap and require no nuts. Photo 2 illustrates the draft gear placement.


If you model the Southern Pacific version as I did, you must blank out the rear number boards. S.P. engines also had additional lighting but, since no detail parts are available, that modification will have to wait.

First use a chisel blade to remove the boss around the number board openings. Next add 5/16- by 13/16-inch plastic plugs and trim the corners to fit. Fasten them with PolyZap. Putty and sand the gaps.

It is most accurate to reveal some of the outline. S.P. crews tended to weld plates in place and the seams were usually very visible.


Rebuilding the radiator (rear) and air intake (front) grills will result in a big improvement in appearance. It involves four parts: the shutters, the grill spacers, the actual grill, and the vertical grill frame supports.

You may model the vertical shutters either open or closed but you should not leave the space empty. On GP20s and on virtually all other diesels except "tunnel motors" it is impossible to look through the hood from one side to the other. I decided to model the shutters closed because it is easier.

I used Evergreen sheet styrene #4527 E-3 Metal Siding, .060-inch spacing but any spacing up to .125-inch would be fine. Cut rectangles slightly larger than the openings, two pieces 3/4-inch by 2 1/4 inches and two pieces 3/4-inch by 3 inches. Fasten them to the inside of the body shell with PolyZap. Make sure the slats are perfectly vertical.

Add shims to the four edges of each opening. They should be .030-inch high by .045-inch deep. Paint the areas now, before you install the grills. Cut the grills from 1/16-inch fiberglass window screen. Cut the screen at an angle so the squares form a horizontal and diagonal diamond pattern. The grills should be 13/32-inch by 1 31/32 inches and 13/32-inch by 2 3/4 inches. Friction will hold the grills in place but I also applied PolyZap with a toothpick.

Cut the vertical supports from 3/32- by 1/32-inch Plastruct "U" channel (the shorter dimension is the depth) and make each piece 27/64-inch long. I cut each a bit long, then trimmed it so friction would hold it in place as I adjusted it. Space them evenly: 27 1/3 scale inches for the radiator; 30 scale inch wide openings for the air intakes. Fasten each with a tiny drop of PolyZap. Use a toothpick to apply it to the seams; capillary action will draw it into the gap. Keep all pieces flush with the shell even if that leaves a tiny gap between the verticals and the grill.


Remove the cab floor by prying the retaining tabs together. Slide out the cab window. It is a tight press-fit. Label and disconnect all wires. Remove the screw-in overhead light bulb. Remove the beacon housing by pressing very hard with a slotted screw driver. Remove the number board light housing by depressing the tabs and remove the entire housing by using a slotted screw driver to push on the two locating dowels.

If you model the S.P., paint the walls and ceiling light green. If you want to be a little more thorough, mask off the overhead light and also paint the ceiling portion of the window insert light green. Then mask the window openings from the inside and spray the outside of the cab, including the window sills, the same color as the body. That way, the wipers will be the same color on both sides of the window.

If you plan to renumber your locomotive, remove the white paint on the number boards with Floquil Diosol and repaint the entire board white. Be careful to mask the headlights.

Larry Larsen and I designed dry transfers to represent number boards with a black background and clear numbers. They are now available commercially. With back-lighting, the numbers illuminate. Those transfers were the only ones difficult to apply. That is because the black background requires you to hold everything up to a light or to work on a light table.

After you apply the black transfers, check to see whether any light shows through; you may need to touch up the edges. Also, after you push the insert into the housing, you will have to run a thin strip of drafting tape around the inside edges to prevent light leaks.


Cut out the inside of the turbo tack. It is unnecessary to cut through the inner roof.

The cab roof edges should be rounded where they meet the cab side walls. See the lead photo.


If you plan to repaint your model, you must sand down the Burlington Northern graphics. Use 000 steel wool. Smooth the edges of the stripes, lettering, and numerals enough to prevent them from producing visible lines once you paint the model and view it in light casting long shadows. I found it necessary to check often and under many lighting conditions to be certain I had removed all the texture. You could try to remove the Lionel paint chemically, but I still think rubbing with steel wool is less work.


In the next issue we will complete the model by replacing the grab irons with ones will make ourselves, modifying the end rails and adding the remaining hardware, painting, lettering and, of course, reassembling everything.


1		Lionel GP20
1 pkg.		Kadee« 820 couplers
1 pkg.		Grandt Line 1108 lift rings
1 set		Larry Larsen One Scale S.P. dry transfers
1 pkg.		Evergreen Styrene #188 S-3 1/8- by 3/16-inch
1 sheet		Evergreen #4527 E-3 metal siding .060-inch
1 ft.		Plastruct 1/32- by 3/32-inch "U" channel
1 ft.		Plastruct 3/32-inch square rod
1 roll 		Belden #8890 black cable
1 pkg.		Molex #1561-60 connectors
12 ea.		Gary Raymond lift rings
5 ft.		.031-inch brass rod
1 ft.		.045-inch brass rod (if 1960-70s model)
7 in.		jewelry chain
12 sq. in.	1/16-inch fiberglass window screen
1 sq. ft.	1/2-inch thick fiberglass insulation


hobby knives, various blades
soldering iron
drill bits: 5/54, #62, #66, #70
small hand drill
power drill
needlenose pliers
putty (such as Squadron Green)
#320 sandpaper
000 steel wool
Phillips screw driver
slotted screw driver
razor saw
masking tape
Bishop Graphics drafting tape: 1/16-, 1/4-, and 1/2-inch
3 by 5 inch index cards
Floquil Paints: S.P. Dark Lark Gray, S.P. Scarlet, Gloss White, Engine Black,
Grimy Black, Rust, Light Green, Boxcar Red, Brass, Old Silver
Testor's Dullcote
pastel chalks: dark gray, black, rust
ruler with 1/32-inch divisions
small rotary saw blade (about 1 1/2 inches)
airbrush and accessories
very small brush
30 inch bolt cutter
various files


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