How to Choose Crankshafts for Your Small-Block Ford Rebuild

Ford utilized surprisingly few crankshaft types in its small-block engines. The 221-, 260-, and 289-ci engines all used the same cast-iron crankshaft, making this crank widely available for three different displacements. This crankshaft is identified with a “1M” in the front  journal area. While it’s easy to assume the 289 High Performance engine had the same type of forged-steel crankshaft also used in the 1969 to ’70 Boss 302 engine that came years later, exactly the opposite is true. The 289 High Performance engine used the same 1M cast-iron crank as the 289-2V and 4V engines – with the exception that it was Brinell tested for toughness and was supported with wider main bearing caps. It was not a highnodular iron crank, but simply a handpicked, standard nodular iron crank. If your faith in this crankshaft is lacking, consider this: Carroll Shelby and his team went racing in SCCA competition, winding this crankshaft to 8,000 rpm, beating Corvettes in the process. With some shotpeening and nitriding, you can trust this crankshaft in your weekend drag racer.

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When it’s time to choose a camshaft and valvetrain, it must be a package deal, with valvesprings and a cam profile that are suited to one another. Really stiff valvesprings with a mild lobe profile will wipe the cam lobe. Springs that aren’t stiff enough for the lobe profile will cause valve floa at high revs. Whenever you purchase a set of aftermarket cylinder heads, never trust the valvesprings and valves that come with the head. Check each and every valve and spring before the head goes on your engine. Chances are good you’ll need a different valvespring for your camshaft application.

 

Here’s a double valvespring for use with an aggressive camshaft. We go with the double spring for greater pressure in order to snap the valve closed more quickly at high RPM.

 

This is a Crane valvespring with a dampener for stability. It’s a mild spring designed for use with a less-aggressive profile.

The 289 High Performance crankshaft is also identified by the same 1M casting number, sometimes with a letter “K” or a Brinell test mark stamped nearby. Dimensionally, the 289 High Performance crankshaft is exactly the same as the standard crank, with a 2.87-inch stroke. Care must be exercised in this regard because it is easy to fake a 289 High Performance crankshaft by simply adding the “K” or Brinell test mark to a standard crankshaft.

The 302’s cast-iron crankshaft, first available in 1968, is identified with a “2M” cast into the forward-most counterweight. Newer 5.0-liter crankshafts are identified with a “2MA” on the journal. Beginning in 1985, Ford went to a one-piece rear main seal, which eliminates the seal lip found on the older 221/260/ 289/302 crank. The 2M crank is not interchangeable with the 221, 260, and 289 connecting rods and pistons. The Boss 302 crankshaft mentioned earlier can be identified by its forged steel design. It can also be identified by either a D0ZE-A or TFE-8 marking on the crankshaft journal. Because Boss 302 crankshafts are so rare, it is unlikely you will stumble upon one cheap at a swap meet. Plus, you really want the whole Boss 302 package. What’s the point of building a two-bolt main small-block with a Boss 302 crankshaft? Ideally, you will find the entire engine and do some dream spinning with your machine shop.

The 351W cast iron crankshaft is easy to identify by observing the “3M” on the forward-most counterweight. It also has larger main journals than the 1M or 2M crankshafts. A forged-steel crankshaft was never available from the factory for the 351W. Like the 302 crank, the 351W went to a one-piece seal in 1985, just like the 302, eliminating the lip and leaky two-piece seal.

The 351C, 351M, and 400M are still considered by Ford as small-blocks. Chevrolet did a 400-ci small-block designed mostly for truck applications. It was lightweight and packed a lot of torque, thanks to its long stroke. We tend to call the 351 Cleveland, and its larger siblings, the 351M and 400M, “middleblocks,” because they really aren’t small-block engines at all. They’re heavier, for one thing. For another, their only sellingpoint was their great-flowing, big-port cylinder heads. The 351C, produced from 1970 to ’74, is rather scarce these days. The 400M, a tall-deck version of the Cleveland introduced in 1972, was destroked to 351 ci in 1975 to make the 351M. This made it cheaper for Ford to produce two displacements using one block casting.

One thing the 351C, 351M, and 400M have in common is that they used a cast-iron crankshaft in all applications. can be stroked to 400 ci by installing a 400M crank. The 351C can be stroked by modifying and installing a 400M crankshaft. This modification is good for well in excess of 400 ci in the super-tough Cleveland.

 

When we get into aftermarket rocker arms, they range from stock iron to stamped steel to cast and forged aluminum. This is an entry-level stamped-steel, roller-tip rocker arm from Lunati Cams. Use this kind of rocker arm with a mild cam profile. There’s less friction thanks to the roller tip. It is also stronger than a stock cast iron rocker arm.

 
 

This is an entry-level stamped-steel rocker arm from Lunati Cams for 1978-up Ford heads with bolt-fulcrum rocker arms.

 

 
Stroker Cranks

It is much easier to build power into your small-block Ford today, thanks to the huge array of stroker kits available for small-block Fords. You can build a higher-displacement stroker small-block for about the same amount of money you can build a 289/302/351W/351C. If you are seeking a low-buck increase in horsepower and torque, you may opt for a budget stroker kit from Performance Automotive Warehouse or Speed-Omotive for about the same amount of money as a basic standard-inch build-up. Affordable stroker kits use what’s already available without expensive tooling costs. We get 400+ cubic inches from a 351W or 351C by machining a 400M crank down to size and dropping it in a 351-ci block. Fit the 400M crank into a 351W or 351C block and make 408 ci. The crank comes cheap because it’s already there. Go to the Chrysler parts bin and opt for a set of 360-ci rods, then machine them to fit the 400M crank. Your Windsor or Cleveland powerhouse doesn’t know the Chrysler rods are in there. Neither will your friends if you keep your mouth shut. Friends will notice when you dust off their doors on Airport Road or out at the drag strip.

We can build an affordable 289/302 stroker by using a 351W crank turned down to size to achieve 347 ci. A custom crank will get you anywhere from 331 to 355 ci depending on the kit you choose.

 

221/260/289/302/351W/Boss 302 Crankshaft Identification

 

351C/351M/400M Crankshaft Identification

 

The stroker kit gets you into all kinds of power for less money. If you’re hellbent hellbent to pump even more cubes into your small-block, it becomes more expensive. A custom stroker kit with a steel crank and H-beam rods gets pricey. But if you’re going to run nitrous or boost, a budget stroker kit will self-destruct the minute you throw some squeeze at it. Build for the power you intend to make. Do it on a budget, throw nitrous at it, and watch the parts fly. A cast crank and forged I-beam rods will not take a nitrous blast without complaint. They will fail – and require you to build another engine all over again.

Written by George Reid and Republished with Permission of CarTech Inc