Muscle Mustangs & Fast FordsHow To Engine
Stock-Block 535HP Screamer - D.S.S. Engine Build
Easy Steps To Building An Affordable Track-Day Terror.
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Almost every year, I get the opportunity to race in Trinidad or Grenada. It could be a road race or a drag event-either way, my crew chief of choice is Mervyn Bonnett simply because of his race-winning abilities. But crewing and racing in the Caribbean involves a lot more than you might think. With staggering import duties and the difficulty of getting spare parts, a crew chief's job becomes one of understanding the nuances of import and export and being able to produce winning performance both reliably and cost effectively.
A few months back, I got a call from Mervyn telling me one of his car owners wanted a "track day" small-block Ford for a car so he can build seat time. This meant the engine had to be reliable and have a power curve that emulated an all-out race engine so as to give realistic shifting practice. All the pointers aimed towards a 331-inch combination that could run on pump gas. Why a 331 rather than a 347? Because a 331 can turn more rpm with less block loads.
As for power, our goal was a target of 525 horses. This was more than achievable with a 331 and would give the block a better chance of surviving lap after lap of punishment.
Having built a couple of 5.0 Fords with D.S.S. parts, Mervyn wanted to stick with success since both engines made reliable power. The modus operandi here is that Mervyn comes to the United States and buys the engine as a kit of parts. He then assembles the engine, dyno-tests it, then strips it back down for shipping as used parts. The teardown also allows him to inspect everything to be sure all is well internally before he goes back to the islands. A failure when the engine is out of the country is a major deal since the duty tax on new spare parts going to Trinidad or Grenada is about 125 percent. Well, all this looked like a good opportunity to see what D.S.S. could produce for a track day engine.
The 5.0 late-model block from D.S.S. came with all critical surfaces machined. This included boring and deck-plate honing, decking, and align-honing the mains. The quality of the block prep was all that we have come to expect of D.S.S. Since blocks are shipped from the company virtually surgically packed, they're ready to take the rotating assembly with little more than a cursory wipe-over of the locating surfaces.
The Rotating Assembly
The rotating assembly decided upon was built around one of Scat's economically priced aero counterweighted, internally balanced 3-1/4-inch-stroke forged cranks. As you can see from the nearby photo, the crank took three pieces of heavy metal in both ends to achieve internal balance. The bottom line is that, in the projected power range of this engine, the crank will be nearly indestructible.
This Scat crank was paired with a set of D.S.S.' flat-top lightweight pistons and pins, which were to be mounted on D.S.S. lightweight billet I-beam race rods. Total Seal rings were chosen to fit the pistons' 1.5mm/1.5mm/3mm grooves. Using high-dollar micrometers both inside and out, the bearing clearances were checked. For the mains, the spread was from 0.0024 inch to 0.0027 inch, which was plenty close enough to our target 0.0025 figure. On the rods, the target clearance was 0.002 inch, and by selective assembly, we arrived at clearances from 0.0019 to 0.0022 inch-again, close enough for all practical purposes.
Piston and Rod Install
To get the narrow Total Seal rings to transition into the bores without damage required a tapered ring installer and a certain amount of dexterity. After all the rods were in, the bottom end fasteners (mains and rod big ends) were given a final torquing. At this point, a provisional turning torque test was done to ascertain that the assembly turned freely. With the rear main seal installed, this assembly should take no more than about 20 lb-ft to turn it. Ours turned at less than 13 lb-ft. The next job was to install the stud girdle onto the extended ARP mains studs.