351W SWAP

The 302 block is notorious for blowing head gaskets. The block has thin walls and flexes under high horsepower. This allows the heads to lift and create uneven spots in the head gaskets which usually results in leakage into the water jackets. To avoid this you have three options: One....you can live with it. (NOT) Two......You can buy an A4 302 sportsman block from Ford. (Expensive) Three.....drop a 351W into the fender wells. For the price of a A4 302 block you could drop a healthy 351W into the picture and with the right parts this could still be a emissions legal car. I have gathered info from across the WEB to find the perfect combo for an 85 Mustang. Some parts may require special modifications to be fully emission legal. You may exclude these or modify to your specific needs.

This information is written towards keeping the car street legal. You can add or remove any parts you wish to meet your needs.

Parts to remove and keep from original 302 block:

1. Cross over tube on back side of heads. This part runs along the back of the heads and around to the passenger side of the motor towards the air pump.

2. Brackets! All your front engine brackets except the ac/power steering pump bracket.

3. Accessories! All current accessories including air pump. (Air pump is for emission purposes only)

4. Cat air tube! Air tube running to the catalytic converter.

5. EGR vacuum sensor. This is located in the back drivers side of the manifold next to the brake booster.  (Keep for emission purpose only)

6. EGR Components! EGR valve and EGR valve plate under carburetor. (Keep for emission purpose only)

7. Carburetor parts! Save carburetor, bowl vent lines, and the air cleaner. (Keep for emission purpose only)

8. Roller parts! (Optional) All parts associated with the roller cam. These only need to be saved if you plan on making the 351W a roller block. There are also conversion kits out that can be purchased for this modification. Note: Machine work to the block is required if you are converting to the roller setup.

Must have parts for the 351W:

1. Oil Pan Kit...................................................M-6675-A58

2. Accessory Bracket w/ AC.............................M-8511-B351

3. Accessory Bracket w/o AC...........................M-8511-A351

4. Flywheel 28.2 oz. imbalance.........................M6375-A302

5. Crank Pulley Spacer.....................................M-8510-B351

6. Conversion Shorty Headers 79-93...............M9430-A58

New parts:

1. 351W block (Complete if possible)

        a. 69-70 351W = Code "M"
        b. 69-79 351W 2bbl = Code "H"
        c. 80-92 351W = Code "G"
        d. 84-98 Truck&Van 4bbl option 351W = Code "H"&"R"

          351W Motor Specifications:
View Specifications            Download Specifications

2. An emissions legal camshaft.

3. Emissions legal heads.

4. If using full length headers purchase an after market full length cat h-pipe. If you are using shorty style headers use a stock 4 cat h-pipe from an 87 to 93 or an after market shorty style cat h-pipe. Note: This may have to be modified to meet up with the heads. The 351W block has a  taller deck height and may create problems when trying to bolt up the stock converter system.

5. Holley 650 to 750 CFM carburetor with vacuum secondary's. Assortment of Jets and secondary springs.

7. Any stock Ford emissions legal 351W manifold from a truck or car. This will vary greatly. The main item the manifold has to have is a EGR valve. If you can find an after market manifold that has an EGR valve I would suggest using it or you can modify any aftermarket manifold following my EGR conversion instructions found here. "EGR Conversion Instructions"

8. 351W Duraspark style distributor this can be found on several 70 and early 80 351W equipped cars and trucks. You will need a steel gear installed on the distributor if you plan on using a roller cam.

Here are some How To's for modifying some of the parts for emissions purposes:

1. The EGR valve needs to be modified on some after market manifolds to keep within the emissions regulations. This is the main trick to get it through the visual part of the emissions inspection. Just slapping on the plate will not work because the plate is larger than most aftermarket manifolds causing a vacuum leak near the passenger side of the EGR plate.

• Have a machine shop fill in the bottom of the EGR plate opening to block off the EGR port completely. (fig.1) This will not pass emissions but may be over looked by the mechanic if he thinks it's operational. Fill in the green area in figure 1.

Figure 1 

• Drill and tap a 1/2" hole in the exhaust gas crossover runner on the manifold (fig.1) and have a machine shop fill in the bottom EGR plate opening slightly because the EGR plate sits out farther than aftermarket manifolds and will create a vacuum leak. Next drill and tap a 1/2" hole in the side of the EGR plate (fig.2) to connect a 1/2" tube from the manifold to the EGR plate. Fill in the green area in figure 2. Tap holes in the EGR  plate and manifold shown in green in figure 3. You can use a 1/2" aluminum line for the EGR tube. This will require you to flare the ends and use compression fittings in the holes you drill in the EGR plate and manifold.

  
Figure 2                                                                                   Figure 3

2. The crossover tube running between the back of the two cylinder heads is too short for the 351W so you will need to cut and lengthen it. You can either weld in a pipe to lengthen it or use a high quality heater hose to make the connection.

3. The carburetor! Well there is a lot of room to play here and many combinations you can use. You can ether trick out the stock carburetor or order a new 600 to 700 CFM vacuum secondary carburetor. Use the two float bowls from the stock carburetor. They are identical to the after market Holley float bowls except for the vent tubes which are required for emissions. No other modifications are required.