Mustang MonthlyHow To Engine
How to Build a Stealth 347
This Small-Block Looks Stock, But It Packs 200 More Horsepower
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You have to hand it to Ford Motor Company for their long-lived 260/289/302 engine family. It was finally replaced by the modular engine in 1996, but the 302 (and its various family members) has been one of the most successful engine programs in automotive history. While there hasn't been a production pushrod small-block in a Mustang since 1995, the research and development of this potent little powerplant continues to expand. Today, increased cubic-inch versions of this venerable workhorse are as common as stock replacement units. And, with the popularity of today's 347 stroker, we want to look at a state-of-the-art 302-cum-347 that may be just what you need for your latest project.
A recent trip to Paul's Automotive Engineering in Cincinnati, Ohio, was all it took to bring us up to speed on what a cranked-up 302 is all about. Paul and his team of Ford performance gurus turn out 347 engine combos on a regular basis, and they were kind enough to let us follow along as they turned a 302 into a 347 stroker that kicked out over 375 rear-wheel horsepower.
While just about every corner-store speed shop offers some form of the 347 Ford small-block, Paul's has separated itself by being a little sneaky about the appearance of the finished product. They've gone the extra mile, outfitting the engine with all of the correct 289 Hi-Po dress for a stealthy combination that will fool most car-show judges and dish out enough power to slap any late-model you might run across. These little details on the exterior can include such things as a date-coded block, painted aluminum heads in the original Ford blue, fuel pumps modified to accept the correct filter canister, intake bolts painted ala Shelby, correct 289 Hi-Po air filter, and a utilized date-coded balancer, distributor, intake, timing cover, and water pump. Put it all together and it's hard to tell if it's a 200-horse stocker or a 400-horse stroker!
Along with our photography, there is a detailed explanation of each part used to put one of these engines together. However, the real craftsmanship comes in making it all work together. Over the last few years, as owners of rare Mustangs have started driving them again, Paul's has done over 30 installations of 347s dressed to look like originals. The project ranges in price from $6,000 to $7,500 depending on what options the buyer needs. Paul prefers clients to have Paul's Automotive Engineering do the build, install, and tuning on their chassis dynos to make sure everything works perfectly before final delivery.
With an additional 200 horses at the stab of the throttle, this is one addition to your Mustang that's hard to resist.
By The Numbers
While the naturally-aspirated version of the stealth 347 stroker made 377 rear-wheel horsepower, Paul also had the chance to dyno Dave Hale's '68 Shelby with an original Paxton supercharger bolted to the 347 package. Set at a conservative 3.5 pounds of boost, the engine generated a best of 423 hp and 404 ft-lb of torque at the rear wheels. As you can see by these numbers, the boosted stroker really starts to strut its stuff at a low 4,000 rpms.