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- EVER bore your engine to gain cubic inches, especially on early factory Ford blocks or you’re just asking for trouble. The easiest way to make an engine bigger is to increase the length of the stroke on the crank. This also increases the torque output of the engine, and “torque” is MUCH more important than horsepower in ANY street or street / strip engine.
- Many people on budgets use donor parts from 351M and 400M engines and crap like that.
- No matter what you do to either of those (stroked 331, 347) engines, a 351W is already bigger by 9 to 25 cubic inches without even doing a single thing to it! Figure a 331 is based on a .030” overbore, and a 347 is also based on a .030” over bore, so you have to figure that in to a 351 also. So when comparing apples to apples, a .030” over 351 is really 356 cubic
- No matter WHAT you do to a 331 or a 347, the 351 is WAY stronger right from the get-go! It is a MUCH stronger block all the way around.
- It has HUGE main caps compared to any 289/302 (including the K code and early Mexican blocks).
- They have MUCH larger ½” main bolts than the 289/302’s 7/16” bolts.
- The crank has giant 3” mains, which is about 10 times stronger than any 289/302 crank.
- The connecting rods are much longer & beefier (5.956” instead of a short little 5.090” on the 302’s), and have much bigger & stronger 3/8” bolts.
- The heads are held down with much bigger ½” bolts as compared to the little 7/16” bolts all of the 289/302’s have - which means they are less apt for head gasket problems,
- The 351W has a taller deck height (9.503”) which is MUCH better right from the get-go than ANY 289/302 with their short little 8.206” deck height. This makes the 351W MUCH better suited for building a stroker than its shorter little brothers.
- The 351W: It is only 1” wider (approximately), and 1” taller than a 289/302 and almost all of the outer bolt-on’s are the same, from the motor mounts, to the valve covers, to the water pump, to the bell housing bolt pattern, to the exhaust bolt pattern, to the spark plugs, to the heads, rockers, timing cover and so on….. all the same as ANY 289/302.
- Put a 289 / 302 side by side with a 351W and take a few steps back. It’s VERY hard to tell the difference between the two. The best part is; it’s a completely bolt-in swap for any early Mustang from 65 on-up, and any early Falcon, Galaxie, Fairlane, Cobra kit car, 5.0 Mustang, or pretty much anything that had a 289/302 sitting in it. Usually all it takes to swap out a 351W with a 289/302 is nothing more than a set of retro fit headers and a low profile air cleaner and you’re good to go.
- A stock 351W has a MUCH stronger block and lower-end, a better deck height, and a better rod angle without even doing a thing to it, plus it is already larger in displacement than both the 331and 347 strokers!
- The 351W is wider between the heads compared to a 302 (the intake manifold is wider by about 1-1/2") and 351 pistons have a different pin height. You can use 302 pistons in a 351 if you stroke it to a 393. Need a 3.85" crank (stock 351W has a 4'" bore and 3.5" stroke), part number: 9-351-385-5955-2311w. C.R. of the 302 piston will be much higher. A piston style that makes 9.5:1 in a 302 will make 12:1 in a 393 stroker. While much of your effective (running) compression depends on your camshaft, a static compression of 9.5 to 10.5:1 is typical for iron heads with US or European 'premium' pump gas (US 92 octane, or the equivalent Euro 98 octane). With your smaller 58cc chambers, this will require a pistons with a 20-24cc dish or from other manufacturer's that are listed as 8.0-1 (or less) compression instead of stock 8.5-1.
Street Engines Like Long Strokes
For lower RPM applications (street engines, hydraulic roller cams, pump gas…etc.) it is probably best if you pick a long stroke. Long strokes would be considered 4.000” to 4.250” giving you 408 to 434 C.I.D. on a .030” over bore.
The longer stroke cranks will give you gobs of bottom end torque and match the “street” type components you will have in the rest of the engine. Plus, the long stroke will give you that seat of the pants feel that makes you smile when you mash the pedal.
Shorter Strokes for the Race Guys
For higher RPM engines and combinations using power adders (blowers, turbos, nitrous), you may want to limit the amount of stroke you will be using. Why? Well, the shorter stroke is able to rev more quickly and handle high RPM’s. Also, as the stroke increases, the piston wrist pin moves higher and higher inside the piston to compensate and piston skirts become shorter.
You need to keep the piston fairly tall to leave room for ring land spacing if the engine will be seeing extreme cylinder temperatures. If you use a piston that is too short in these powerful engines, you will see piston failure in no time. Short strokes would be 3.750” to 4.000” keeping you in the 383 to 408 C.I.D. range using the same 4.030” bore. Many boosted engines are built with the shorter strokes and big bores (4.125” or bigger) resulting in bigger C.I.D., without the sacrifice of the weak pistons needed with longer strokes.
- By the way, a 351W with aluminum heads and aluminum intake manifold weighs LESS than a stock cast iron 289!
- OEM 351W blocks come in two deck heights: 9.480” and 9.500”. The shorter blocks were standard for ’69 and ’70, and the ’71 and later blocks measuring an extra .020” higher. This is an important specification when choosing your rotating parts so you don’t end up with pistons sticking out of the top of the deck.
- Both has 5/8" (18mm) spark plugs
- Since the deck height is taller the intake manifold is wider on the 351w than on the 302;
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