BUILD A 348HP 302
WHETHER YOU FOLLOWED ALONG FOR PART 1 OF THIS WALLET-FRIENDLY SMALL-BLOCK REBUILD OR NOT (mustang-360.com/how-to/engine/ 1806-budget-350-horse-302-part-1the-machine-shop), you won’t want to miss out on Part 2. This time around it’s all about adding a healthy dose of power to a run-ofthe-mill 1971 302 small-block. We’re taking what could be an average rebuild and putting a small aftermarket spin on it by tossing out the stock top end in favor of some goodies we picked up from Speedway Motors.
With a set of reasonably priced aluminum heads from Flo-Tek as the catalyst, we spec’d out a handful of other top-end parts in hopes of bumping the little 302 up near 350 horsepower. That number might not sound impressive in the days of 1,000hp Internet heroes, but if you’ll remember, small-block Fords from the early 1970s weren’t pushing too far past the 200hp mark. So if you were being pulled around by a stock 302 like we were, you know you’re going to feel an increase of 100plus horsepower.
So what was the plan of attack, you might ask? Well, the aforementioned Flo-Tek heads were what really got us thinking. Pre-assembled (valve seats, valves, valvesprings, and retainers), these things are going for around $400 each, so at $800 for a pair of performance aluminum heads, we were off to a great start. At that point it was about picking the right assortment of supporting mods, starting with the intake manifold. This was probably the easiest decision, and since street-driven performance was the goal, an Edelbrock Performer RPM Air- Gap was a no-brainer. Time and time again we’ve seen these make solid power at the top of the powerband without sacrificing low-end torque and drivability.
Next up was camshaft selection. We wanted something that would take advantage of the higher-flowing heads and intake manifold, but again, not give up too much down low. We also wanted to keep it cheap and simple, so we stuck with a hydraulic flat tappet. What we got from Speedway Motors was a cam with an intake and exhaust duration of 219/233 at 0.050 and .477/.510 lift with 110-degree lobe separation. Finishing off the valvetrain, we went with a set of Speedway Motors 1.6:1 roller rocker arms with a 3/8-inch stud to match the Flo-Tek heads.
To get fuel and air into the engine, we could have gone EFI, but since the word “budget” is in the title of this story, we decided to keep it simple and affordable. Thus, we opted for a Holley 650-cfm Double Pumper. Then to dress things up, we went for a set of Speedway Motors black aluminum, fully finned valve covers and matching 12-inch oval air cleaner. And no, we didn’t forget about spark; our 302 was already fitted with an aftermarket HEI all-in-one distributor that was working well, so we just cleaned it up and got a set of MSD Street Fire plug wires and fresh plugs.
The end result was not only nice to look at (yes, we’re a bit biased), but it also met our expectations in terms of performance. Keep on reading to see how we got from a bare block and a pile of parts to a 350hp mill that’s ready to go.
First up we get ready to check the crankshaft journal clearance by installing our Clevite main bearings in the main journals and caps. Remember, install notch to notch and press firmly into place, ensuring each end of the bearing sits flush.
Unless you really trust yourself, it’s best to have a second set of hands when dropping in the crankshaft—don’t forget to thoroughly cover all bearing surfaces in engine assembly lube. Adding some lube on the inside of the rear main seal is also a good idea so it doesn’t catch on the crank.
This could have been done earlier or later, but next we tapped in the core plugs using non-hardening aviation sealant on the edges.
Set all the main caps in place and then torque to spec, starting from the center and working your way out.
Next we installed the two-piece rear main seal with the groove facing inward and used non-hardening aviation sealant on the back and the top edges. Whether you install it flush or offset is up to you, but some claim that leaving one side higher than the other is better at retaining oil.
After torquing all the main bolts to spec, we checked crankshaft main journal to bearing clearance using a dial bore gauge and micrometer. If the clearances are too tight or too loose, it’s better to find out now than just cross your fingers and pray it all goes well when you fire the engine for the first time.