There are a few things to know when swapping from a 302 to a 351 in a 90 F150. You’ll need to swap the headers and y-pipe as the 351w is wider and uses different pieces. Also, the 351 is a 28oz balance motor vs. the 302s 50oz, so you’ll need a different harmonic balancer and flywheel/flexplate. The oil pans are different. The newer engines have a hole for the dipstick through the base of the block, whereas the older motors don’t. I used an older block and that caused a bit of a problem. I was able to find a truck pan that had a provision for a screw in dipstick tube. On the top side of the motor you’ll need a 351s specific intake. Again, because of it’s width, the 351 uses wider fuel rails and EGR tubing across the back of the motor, which I was able to modify.
I also had to rewire the FMS MAS injector harness as the 351w has a different firing order. Because my engine is actually a 408w stroker, I used bigger injectors and upgraded to a bigger meter calibrated for the new injectors. The knock sensor relocates to the side of the 351 intake from the rear of the 302 – and will require lengthening the wires. Although the 302 and 351w motormounts are the same, I bought new ones while I was doing the swap – and good thing because the rubber on the old ones was in sad shape.
- 408w stroker shortblock – Probe pistons, Eagle H-beam rods, cast crank
- worked E7 castings fully ported with bigger valves
- oil pan with provision for screw in dipstick
- truck EFI 5.8 upper and gasket matched lower intake
- Summit/Pacesetter shorty headers
- Bassani y-pipe w/cat
- FMS MAS EFI conversion (rewired for 351w firing order)
- 30lb injectors
- 80?mm Bullet meter
- 351w EFI distributor
- valve covers to clear rockers
- Comp Cams Xtreme 4×4 cam; 270/278 duration, .512/.531 lift