Dart’s New Iron Eagle Pro SBF Blocks Make Custom Features Standard

Available in all four popular SBF deck-heights, and both 4.000-inch and 4.125-inch bores, there are ten part numbers for the Dart Iron Eagle Pro, as the 9.200-inch offering is available in both 302 and 351C main sizes.

For a long time – ever since its introduction, really – the Dart Iron Eagle engine block has been the go-to iron block of choice for high-power pushrod applications. Between the additional features, additional strength, and wide variety of options, it ticked almost every box on the wishlist of high-end engine-builders across the country.

As the market and technology evolved, the field started narrowing considerably, and everyone started looking for more and more of an edge over the competition. That led the small details being addressed by more and more customers. Dart took notice of the race-specific modifications that were being made, and decided to incorporate those into a production block, spawning the Iron Eagle Pro engine block.

“The Iron Eagle Ford Pro was developed for maximum competition,” says Mike Sanders, Sales Manager at Dart. “It’s the ideal foundation when using large turbos, large blowers and heavy nitrous applications.” To that end, the features incorporated in the Iron Eagle Pro might not be appropriate for every small-block Ford engine build.

One of the largest visual indicators of the Iron Eagle Pro, over the standard Iron Eagle is the blank area where the SBF’s oil filter usually is. That keeps additional material at the front of the block, increasing strength.

“I would say [the Iron Eagle Pro] is a good idea on any power-adder engine seeing 2,000 horsepower or more and/or if you are running an alcohol engine with over 30 psi of boost,” says renowned engine builder Jon Bennett of Bennett Racing Engines and KBX Performance.

Advanced Competition Features

A majority of the revised features are based in the oiling system of the block. The most obvious of which is the blank area on the front driver’s side of the block, where oil filter is traditionally located on a small-block Ford. “We removed the factory oil filter mounting and -10AN oil feed to keep more material in the front of the block,” Sanders says. “That makes the block oiling system compatible for dry sump or external wet sump only.”

The priority-main oiling system has been revised, and the main oil feeds have been reduced in size from the standard .439-inch feed hole, to a .250-inch passage which increases strength in an area that has been seen to be a failure point in extreme applications.

The additional material not only increases the absolute strength of the block, but also its rigidity, which can come into play in high-horsepower, high-boost applications. “An external pump is a must, due to the oil filter pad being deleted but there are plenty of street cars with those oiling systems,” Bennett says.

In addition, the priority-main oiling system has been revised to, again, enhance the block’s performance and strength. “We reduced the stock SBF main oil feeds from .439-inch down to .250-inch,” says Sanders. “If the customer is running a roller style cam bearing, we can eliminate the crank to cam oil feed altogether, to increase main strength.”

For those using traditional Babbit cam bearings, the cam to crank oil feed has been reduced to .090-inch.

At the rear of the valley, the traditional lifter crossover has been eliminated and blanked, once again adding strength to the block. You can see the 1/2-inch NPT oil feed port below.

Bennett cites this as an outstanding change for extremely high-power applications.

“The failure point of the standard block is the main oiling hole, and usually the number one main is where most failures occur. The Pro Block has reduced that size of that hole giving the main bore more material after the oil hole,” says Bennett. “Since 99-percent of the high-power engines we build use roller cam bearings the cam bearing oil hole is not needed. The Pro Block has deleted that hole as well, adding even more strength.”

With strength being a primary concern, as this block is designed to be used in a realm where 2,000-plus horsepower is common, the main cap fasteners have been upgraded as well.

“We have upgraded the Grade 9 ARP main bolts used in the standard Iron Eagle 4-bolt main caps with Grade 9 ARP main studs,” Sanders says. “The studs create more consistent clamping on the main caps, which in turn reduces cap walk.”

In pursuit of an ultimately capable iron block, Dart has selected a high-strength iron alloy, which comes in at 220 Brinell hardness, which is quite stout for iron. It also comes with the option of screw-in freeze plugs, and the block can be machined without the distributor bore, for front-drive distributors and coil-on-plug applications. By leaving that area unmachined, additional strength can be added to the combination.

At the front of the block, there are several updated features. The first is the revised cam-to-main oil passage, which has been reduced to .090-inch for Babbit-cam-bearing applications, and eliminated altogether for roller-cam bearings. The distributor mount can also be eliminated for those who opt for a front-drive distributor or coil-on-plug system.

Deck Heights and Main Sizes

With so many competition-specific features, you might be wondering about what combinations are going to be offered in relation to potential engine displacements. The short answer is, “all of them.” All four small-block Ford deck heights will be offered, with the 8.200-inch and 8.700-inch models coming with 302 main bore sizing, while the 9.500-inch deck height comes standard with the 351 Cleveland main bore diameter. The 9.200-inch deck height option is available with either 302 or 351C mains.

All five of those potential combinations are available in either 4.000-inch or 4.125-inch bore sizes, with a maximum finished bore size of 4.185-inches across the board, for ten part numbers across the Dart Iron Eagle Pro lineup.

“The Iron Eagle Pro provides a little insurance, per se, in the design upgrades over the standard Iron Eagle block,” concludes Bennett. With all the popular small-block Ford combinations covered, the Iron Eagle Pro engine block offers high-end custom features in a production item, which makes a great base for an all-out competition engine.

Racers like Joel Greathouse have seen the first-hand benefits of the Dart Iron Eagle Pro engine block, thanks to Jon Bennett. Greathouse’s Dart-based KBX 400U engine has powered his Mustang into the 4.70s in the eighth-mile.

Article Sources

About the author

Greg Acosta

Greg has spent over a decade in automotive publishing as Senior Editor of Race Pages magazine. In his free time, he is a firearms instructor and volunteer in the police armory.
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