1985 Bronco , 300 cubic inch inline 6 engine, 4 x 4, 4 speed transmission
The Bronco came to the shop in fair shape with numerous minor complaints and in need of refurbishing.
The first issue was with the rear window failing to operate. The side runners and motor had been replaced in the past, but nothing was done to ensure the longevity of the repairs. Winding Road Classics completely disassembled all the components of the system and found that the main cause of failure to operate was the safety switch at the side of the door. This switch ensures that the window can’t be operated when the tailgate is down. A replacement could not be found, so I took it apart, cleaned it, and reassembled it, tested it, and it was fine.
Second issue that was addressed throughout the project was weatherstripping. At first only the major pieces were replaced, thinking that they had the most usage and needed the most attention. After all was said and done, every piece on the truck has been changed. A leak test was performed at the car wash with the sprayer at different angles and everything came out just fine. The biggest leak that had damaged the floor and floor covering ended up being the cowl. Once again, from the forums, this is another problem area on this era of Broncos. After removing the cover, all of the leaves, dirt, pine needles and other debris were removed and then rinsed out through the drainage channels on each side. These were cleaned from the underside. After cleaning, the rust areas were treated with Ospho, sealed, and painted with rustoleum.
The next issue that was addressed was the rust and holes in the floor. The passenger side was the worst, with two places that were rusted through removed, patches fabricated and welded in, and the rest of the floor was treated with Ospho, cleaned, and painted with rustoleum. Other places that were patched were on each side behind the front seats. Both sides were rusted at the corner where water had come in. This led to changing the seals on the top. Another hole had rusted through on the right rear floor near the spare tire holder. All of these were painted top and bottom after repairing.
A new electrical fuse panel was installed from American Autowire. This was necessitated mostly from the engine work, but it also helped by getting rid of the computer module and emissions controls that were hindering the motor. Fuses are easily obtainable from any auto parts stores, and the fuse panel is labeled for the usage of each fuse. It is located on the driver’s side center, under the dash.
New vinyl flooring was installed front to rear. Fibrous padding is under the pad in the front, and the rear was underlaid with outdoor carpeting as padding. A new dashpad was installed on the dash and painted to match. New side panels were fabricated in the rear. They are made from fiber reinforced plastic sheeting, painted, and mounted like the original cardboard ones. The door panels, kick panels, and pillar covers were also cleaned and painted to match. Some were sun damaged and faded, others were okay. Painting has matched them all with the main dash. While the dash was off all of the rust from the leaking windshield and cowl was treated with Ospho and parts were repainted. The Ospho leaves a protective coating that will prevent rust in the future as well, though all leaks have been addressed. While the engine was out, the engine compartment was degreased, cleaned, and painted.
The engine from 1985 was saddled with emissions equipment, a dreadful computer feedback single barrel carburetor, and a non-advance distributor. All of these in conjunction with a restrictive intake and exhaust made for a good engine that was starving for air and fuel. Adding to this were leaks, though a good hot rodder knows that engines don’t leak, they’re just marking their territory.
Beyond the normal rebuild procedures for any engine, this 300 inline 6 cylinder received the following special treatment options.
Comp Cams 260H camshaft
Comp Cams lifters, springs, and rocker arms mounted on screw in studs with custom guideplates.
Manton custom length push rods.
Offenhauser dual plane intake, which features smaller runners on the low side to increase velocity at lower rpms. This helps with throttle response and fuel atomization. The upper side opens up with the secondary part of the carburetor to double the airflow and provide all the air the engine needs with the increased fuel. A good “best of both worlds” intake. Intake was fitted with a coolant fed heat transfer to aid in fuel atomization. Originally this was accomplished by being attached to the exhaust manifold. It mainly improves around town driveability.
Holley 390 cfm carburetor, recommended for the above intake.
The exhaust manifolds are from a later model 300 engine that had electronic fuel injection (EFI) intake. They are free flowing and in my research others have tested them to be almost as good as full headers. They are much easier to package into trucks though. They are routed to the exhaust with a Walker two into one adapter made for this purpose. Exhaust manifolds are painted with a high temperature paint. The exhaust is new back to the original muffler, replacing the catalytic converter.
The ignition system is a replacement distributor with vacuum advance which is controlled by a Duraspark 2 module. This system was used by Ford throughout the 70s and is both reliable and readily available if problems are encountered.
Emissions parts and feedback vacuum switches were mounted on the valve cover at the rear of the engine. All of this was removed and the mounting holes welded up and sanded smooth.
The engine itself was completely disassembled and taken to a sonic blast cleaning at the local machine shop. It received new freeze plugs, bearings, seals, gaskets all the way around. Careful measurements were taken at every stage to ensure that the crank, rods and pistons were within specifications. Plastigage was used to check the oil clearance on all bearings. The block and head and various covers were painted “Ford blue” prior to assembly and allowed to cure. Brackets and various attachments were painted black for contrast. Intake and carburetor were left as manufactured.
A new clutch and pressure plate were installed.
The right rear brake cylinder was leaking. Rear brakes were completely redone with new cylinders, brake shoes, emergency brake activators, and adjusters. While working on the rear brakes, new rear seals were installed and also differential gasket. Differential gears were inspected and new gear oil with traction additive for the tractionlok system was added. Front brake pads were replaced. All brakes were bled and are activated by a new master cylinder and power booster.
Engine as it arrived in the shop.
Engine on the stand.
Engine after reinstallation.