Half-Price Hardware: How To Build A Budget 347 Stroker Motor
How to build a fun-time 347 for about half the price of an all-out race engine

By Tom Wilson
Photography: Tom Wilson		    
     
Horse Sense: The newest part on this budget engine is the Funnel Web intake manifold from the Parker Company. Probe/Coast hasn't run this intake, nor have we, so it'll be fun to see how it does on the dyno next month.

Some magazines make a living screaming headlines about Junkyard Warriors--we're not one of them. Like everyone else who's been once around the high-performance block, we realize there is no such thing as pocket-change racing or even sterling street performance. Speed costs money, and that's that.		  

 The trick to real-world budget performance is learning what you can live without while getting your speed fix. For example, the goal here is to build 500 hp from a small-block Ford and not go totally broke in the process. By not going broke, we have to swallow once, take a deep breath, and admit it still takes $7,733.06 to build a turnkey 500hp engine, and for that we aren't going to get everything. We'll have to give up the last word in durability--no bulletproof aftermarket blocks--and there is little budget for extensive hand-porting or expensive systems. Such an engine will have to be built from off-the-shelf pieces, and nothing exotic at that. And while six or seven grand is still a pile of money, it's a long way from the $13,000 to $14,000 it takes to assemble a full-on forged and Dart-blocked race engine these days.  

Severo Diaz, known as "Pinto" around the shop, gives the budget 347 engine a final couple of checks. While not a low-buck engine, this 347 takes a stand in the reasonable dollar range while still reaching for 500 rowdy horsepower.
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Probe and CHP

Don't worry if you're a bit confused by the relationship between Probe Industries and Coast High Performance. The two companies are closely aligned and share much of the same physical plant, but Probe is the manufacturing company and Coast is the sales side of the organization. So, if you want to purchase an engine, call Coast High Performance and buy one of theirs, and understand it will have Probe pistons inside it. Got it?

 

For our purposes we'll run the engine carbureted on the dyno to see how close we came to our power goal. Carburetion is less expensive than fuel injection, unless, of course, you already have a tunable fuel-injection system you can modify to work at high rpm. That means a possible slight loss of driveability, definitely less fuel economy, and no hope on the emissions front.

  


All these parameters lead us to what the typical bracket racer would recognize as a good budget build. The first step to power is displacement--there is no replacement for displacement--and the best bang for the cubic-inch buck is, of course, a 347.

The next step is to pack as much air as practical into the (Procomp Electronics | Motorsport) cylinders, meaning a high-flow cylinder head and a really big cam, then squeezing it hard via elevated cylinder pressure to get some work out of it. To date, a turbocharger is the most efficient way to squeeze air, but that--and all other forms of supercharging--is off (budget) limits. Instead, we'll do it the old-fashioned way, with a generous dollop of compression.

  

Probe uses a variety of crankshafts in its engines, but we most often see Scat cranks when visiting Probe. Our budget 347 was no exception--it uses this 3.400-inch-stroke Scat cast-steel crank. Cast in China and machined in the United States, the Scat crank is a bit heavy and features now-standard counter weighing and profiling practices; it is quite stout and should prove durable. It's the centerpiece of the 347 stroke job.
     

What we've spec'd out is a 347 stroker packing a big, mechanical camshaft, decent heads, and a free-flowing intake manifold and carburetor combination. That's just the sort of thing Probe is used to putting together for its bracket customers, and we followed along as they demonstrated how they would put together a budget 347. This month we're showing the parts and highlights of how they went together; next month we'll strap the engine to one of Westech's dynos to see how the power comes out.

  


A final word on trading dollars for performance: This engine should party hearty, but it will feature a choppy idle, thirst for premium gasoline at the least, won't last 100,000 miles--and don't even think about emissions. But it will scoot, and for a Saturday-night shaker, bracket or other fun machine, it should provide a grin made all the larger because all that speed didn't cost so much.		  

Called Machine Beam Rods by Probe, these are good budget connecting rods. Forged and fitted with ARP hardware, they are a smart choice for a powered-up, but not overpowered or screaming-rpm engine.

 

  

 

 

    

Probe saves some money on its machined beam rods by not finishing the surface of the beam's "bowl," which leaves this rough surface. If that bothers you--it shouldn't on the majority of fun-car engines--Probe has plenty of other, more finely finished rod options.
  
Probe is famous for its pistons, and for our budget bracket motor the company reached for the SRS forged line with a big 9cc pop-up to raise the compression ratio. This dome shape works with all inline valve heads, save the Twisted Wedge and Edelbrock Victor castings with their canted valves.		  

The standard piston pins with a 0.150-inch wall thickness were used, and they're plenty strong enough for 500 hp in a budget engine. They're packaged in the SRS piston line, and they're made from 1018 material and are hard chromed. Probe offers tool-steel pin upgrades in various thicknesses.
         
   

Rings and bearings used in Probe's budget build are its standard Perfect Circle and Clevite fare. The ring package is the now rather standard 1/16, 1/16, 3mm sizing. With the piston pin in the oil ring groove, an oil-rail support is included with the piston. It supports the oil ring and keeps it from rotating in its groove and thus working its ends out of the groove. According to Probe, the oil-ring groove climbing was an issue years ago, but today's heavier rings don't have that problem, which makes the oil-rail support a belt-and-suspenders approach.
  

For a budget build such as this, Probe uses an Elgin EM-68HV oil pump. It's packaged with gaskets and a standard oil-pump driveshaft, which Probe replaces with its in-house-built heavy-duty driveshaft. Beefy oil-pump drives are--and should be--a staple of all but the lowest lo-po small-block engine builds.
  

Low budget or not, having more oil on hand and keeping it away from the rotating assembly is important to any performance engine build. Probe fitted this engine with a basic Canton deep-sump pan. There's nothing fancy here--just a deep sump with no scraper or windage tray, and no trapdoors or other flow controllers. Fel-Pro pan gaskets are used to ensure sealing, and Canton supplies an oil-pump pickup and dipstick to match the deep-sump pan. Probe makes a windage tray that'll work with this combination, but it wasn't fitted to this engine.
         
   


Probe builds its small Fords with a new replacement front timing-chain cover. It's a universal fit item with a dipstick hole and is supplied with a small 3/8-inch welch plug (think "tiny freeze plug") to seal the dipstick hole if a block- or a pan-mounted dipstick is used.
  

Because it is designed to work with either early or late Ford engines, Probe's replacement timing cover features a fuel-pump mounting boss. It isn't needed for fuel-injected applications, of course, and may or may not be used in carbureted cars depending on the fuel pump used. In such cases, a simple block-off plate is fitted.
  

Professional Products is a low-cost engine-parts supplier based in the United States, but the company sells parts that are almost exclusively sourced from overseas. With its extensive line of budget parts, the company figured prominently in Probe's dressing of this engine, including this elastomer-style harmonic damper. An SFI-approved unit, this damper is normally what Probe fits to its complete engines.
         
     

Iskenderian ground the budget 347's mechanical flat-tappet cam and supplied a set of its matching lifters with EDM oiling holes in the bottom to flood the cam lobes with lube. The cam measures a healthy 263/272 duration at 0.050-inch lift, along with 0.592/0.608-inch valve lift, and a valve lash of 0.016/0.018-inch. Designed for carbureted duty, the lobe center is 110 degrees. We're expecting a choppy idle and a 7,500 to 7,800 top end from all this.
  

McCord used to make this graphite head gasket, which Probe believes is forgiving and totally leak-free. Probe bought the final 5,000-gasket supply from McCord, so the company will use them for a while. When they run out, Probe will source a similar gasket, even if it has to be custom made.
    
         

   

Pro Comp (Procomp Electronics | Motorsport) also supplied the cylinder heads. They're close copies of an Edelbrock Victor Jr. casting, giving them a large 215cc intake-port volume. Troy Bowen at Ford Performance Solutions set up these heads with the proper spring heights for Probe. He also did the valve job and a small amount of bowl porting on these units.
  

The heads were extensively CNC ported, to include all ports and the combustion chambers. As you can see here, the CNC program ran out of casting material to whittle at the outer floor of the exhaust runner, but that shouldn't amount to anything.
  

A glance at the combustion chamber in the Pro Comp (Procomp Electronics | Motorsport) heads shows the 2.055x1.600 stainless steel valves and CNC-machined witness lines. With a modern chamber, these should prove to be fast-burning, high-motion heads.
         
   

Here's something different--a Funnel Web single-plane intake manifold, as built by the Parker company of New Zealand and supplied by Pro Comp (Procomp Electronics | Motorsport). As Probe stated, "It's supposed to work great if you can fit it into a car." By that they mean it's a rather tall intake, so plan on a scoop atop your 5-inch-rise hood. The intake is fitted with bosses for injection or nitrous, along with drill-out fittings to allow a rear-water crossover pipe.
  

There's nothing secret about putting the rotating assembly in the budget 347's block, so we're skipping the assembly photos this time around. The block is a 1974 production casting, which makes it distinctly stronger than a late-model, thin-wall, 5.0 casting, but not as beefy as a modern aftermarket block (nor anywhere near as pricey). This block took a 4.040-inch bore, which isn't unexpected in a block this old.
  

At a hopeful 500 hp inside a stock two-bolt block, Probe opted to install one of its steel, blanchard-ground main stud girdles. The steel has expansion characteristics similar to the block's main bearing caps, which should provide some main-bearing rigidity.
         
   

Several good aftermarket timing chains are available for small-block Fords, and Probe uses a variety of them in its engines. Probe engines usually come with a mechanical fuel-pump eccentric. It's a must with a mechanical fuel pump, naturally, but doesn't hurt a thing should an electric fuel pump be used.
  

June and "Pinto" were the two Probe techs who assembled the budget 347. June fit the (Procomp Electronics | Motorsport) cylinder heads and, as shown here, he likes to do this with the engine on its side. He thinks it's easier, and stray stuff doesn't fall down into the short-block that way.
  

The Pro Comp cylinder heads are fitted with 1/2-inch head-bolt holes, while the early block has the smaller 7/16-inch bolt holes filled with like-sized ARP studs. To retain some stud support, these shouldered washers were fitted to all head-stud holes.
         
   

Degreeing the cam and dressing the valvetrain was also standard stuff, so photographically we'll again jump to conclusions. The pushrods came in at the 7.200-inch range, which is perfectly normal. The rocker arms are 1.6-ratio Probe roller-tip, roller-trunion aluminum units. Valvespring pressures are 130 pounds on the seat--we'll see how that works on the dyno at 7,800 rpm.
  
June also enjoys mating the water pump and timing cover on the bench, then fitting the assembly to the short-block. The water pump is made in the USA and sold by Probe as a private-label part. Probe's been selling this water pump for three years and none have come back, so it seems to be a good pump.		  

With the engine just about assembled and with little chance of stray parts falling into it, the oil pan was installed. The first step was to install the oil-pump pickup, which attaches to one main-cap stud and the oil pump at the other end.
         
   

As with all small-block Fords, the oil-pan gaskets and rubber end seals should be carefully aligned and given a touch of sealant. Pay attention to getting these gaskets flat and interlocked as necessary to avoid oil leaks.
  

Bolting the big Funnel Web single plane into place was straightforward. We suppose the bolt holes in the manifold are elongated to accommodate large angle-milling cuts.
  

During our photo shoot, the final fitment was a Pro Comp (Procomp Electronics | Motorsport) distributor. It's another budget part (you'll need to assemble your own wire-terminal ends), but it's said to have a good magnetic pickup and other internals. For dyno duty, we'll fit either a set of Probe's aluminum valve covers or use our usual Comp Cams polymer covers. Furthermore, the water pump might come off in favor of an electric unit. Either way, it promises to be fun.
         

 


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what carb did you use , what size jets ? i have just started this exact build for my 1964 comet calanti , using a rug style toploader ( over drive 3sp ) with a 4 56 9in ford diff thanks for info mike

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to see how it does on the dyno next month.

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So what did the dyno come up wit??

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