The old adage of there is no replacement for displacement will always ring true, especially when the topic of a pump gas engine is the center of conversation. That cliché, unfortunately, gets lost from time-to-time during these days of the force-fed modern LS small-block engines. We've seen our fair share of boost-pumped LS bullets that make in excess of 1,000 hp and even as high as 1,500 hp. The price tags are as impressive and mind-boggling as the output of the latest small-block from the General. Adding to the complexity and cost are the turbo/supercharger units and associated plumbing, EFI, massive fuel system, and electronic controllers--you can start to see a dim picture being painted of a timely and costly installation associated with that type of build. Fear not, there are alternatives and we will revert back to the big engine comments made above--bigger is better.
We put the challenge out to Scott Shafiroff Racing Engines (SSRE) to give us a formula to make over 900 hp in naturally aspirated trim, fit under most conventional cowl induction hoods on common muscle cars, and drink 93 octane gasoline. SSRE proprietor Scott Shafiroff said the task was tricky, but attainable. He prescribed his 598 Twisted as the solution. It's the newest crate engine from the longtime engine builder. The Twisted will simply bolt into your car without having to fabricate custom parts that people associate with most force-fed applications.
"A few years ago we began offering 598ci engines that use a low-deck block. It was a way to give our customers extra power, but stay away from the taller deck blocks that are used for the 632s," says the New York-based engine builder. He continues, "I know most people don't build a low-deck 598 because of piston and rod design issues, but SSRE has some tricks that make it a reliable and durable combination."
1 Dart prepares the low-deck block to Shafiroff specs in order to achieve 598ci what they
2 The 4.500-inch stroke crankshaft is laid in the Dart block. An Eagle 4340 steel crank i
3 Each engine is professionally assembled by a team of seasoned builders. Here, the crank
Scott doesn't want to divulge the secret in making 598ci from a low-deck engine, but let's just say that the fix involves a pretty savvy trick. SSRE works with Dart on a propriety block design that allows for a properly designed piston and correct connecting rod length. The ultimate advantage to a low-deck engine is that it will fit under the typical cowl induction hood on most muscle cars. SSRE's regular 598ci engine makes 775 hp and Scott said the new Twisted was going to make over 900. We dared him to put his money where his mouth is on this one, and we'd bring the pump gas. We put up a dollar for this gentleman's bet and it is a buck we'd be more than happy to fork over if the Twister cranked out 900 hp.
For those who don't know Scott, he is a former NHRA Pro Stock racer and Pro Mod engine builder who has been designing and building engines for over 40 years. His racing bullets have set records and won championships in all types of racing. The Ultra Street line, which is home to his pump gas combinations in both big- and small-block configurations, came about over 20 years ago as more customers began looking for his expertise in the street market. Today there are dozens of different small-block and big-block engines for sale through SSRE for both race and street applications. Each one is a proven package with the right combination of parts and professionally assembled.
Another nice feature is that SSRE dyno tests every single engine before leaving the shop and Ultra Street bullets come with a warranty. Scott likes to remind us that SSRE engines are engineered by them so you can simply bolt it in your car and go have fun later that day. The Twisted 598 was designed with the same premise of quality and performance.
4 The custom pistons are wrapped with Total Seal rings, and here you can see the coating
5 One of the factors contributing to a 93-octane pump gas engine includes the compression
6 ARP L19 bolts secure the rod caps of Eagle 4340 connecting rods. The rods measure 6.535
7 The other piece to the pump gas puzzle is the cam. The custom grind features 0.739/0.74
8 An assortment of gauges, a degree wheel, and a pointer are used to degree the camshaft.
9 A Cloyes timing chain is covered with a chrome timing cover and a Shafiroff timing poin
As mentioned earlier, the SSRE gang turns to a specially prepared Dart low-deck iron engine block to begin its run up to 598 cubes--an aluminum engine block is optional. The bores are enlarged to 4.600 inches, while the Eagle 4340 steel crankshaft offers a 4.500-inch stroke. The standard connecting rods are also sourced from Eagle and are 6.535 inches long. For those looking to add nitrous or step up the rotating assembly, a Callies crankshaft and connecting rods are available as upgrades.
There aren't too many tricks to running 93-octane pump gas other than keeping the compression ratio in check as well as the proper camshaft. SSRE limits this big-block to 10.95:1 and the JE pistons feature a coated side-skirt for oil control and reduced friction.
The short-block is fairly typical for an Ultra Street 598ci engine, and the difference between Twisted and the Big Dawg 598 (775 hp version) resides on the topside. Airflow is the key to more power and SSRE adds Brodix 383 Head Hunter oval port heads that are fully CNC-ported. A Brodix Big Mouth Dominator intake manifold is on top and comes port-matched.
A mechanical/solid roller camshaft controls the massive 2.35-inch intake and 1.85-inch exhaust valves. The specs were specifically designed by SSRE for this engine, and as Scott puts it, "The cam gives the engine a nice strong idle and great street manners, but it still makes the power."
The cam features a 114-degree lobe separation and the intake lobe lift is 0.739-inch each while an octave of exhaust valves are opened slightly more with a 0.741-inch lift. The duration is a healthy 269 degrees for the intake and 276 degrees for the exhaust.
10 An ATI balancer is pressed on using a hydraulic press for an even and easy installatio
11 A Moroso oil pump and street/strip oil pan bolt to the bottom of the engine.
12 The short-block assembly is done, and we were ready to add the top-half of the engine.
Some enthusiasts might ponder the use of a camshaft with more exhaust lobe lift than the intake side, as typical cams are the other way around. We were curious, too and Scott gave us his typical smirk and said the camshaft was one of the reasons they sell packages--everything is designed to work together, including obscure cam profiles. He used a combination of scenarios to come up the specs and it goes back to pump gasoline limits and the efficiency of the Brodix heads. The team tried several different cam profiles using conventional and unconventional thinking, with that camshaft providing the right power and drivability. Other cams made a little more power, but it came at the detriment of drivability, a factor Scott wasn't willing to compromise for a gain in peak horsepower.
The Twisted retails for $15,950, less carb and ignition, but each is available from SSRE. An added bonus to the base price tag is free shipping in the continental 48 states, and a 2-year warranty. Shafiroff has the ability to ship overseas anywhere in the world.
Shafiroff bolted the engine to the dyno and added one of the SSRE blueprinted and calibrated Holley Dominator kits to the top of the bullet for the final results. He suggested that particular carburetor for this application and it is an optional item that will increase the base price. As photographed for this story with the Holley 1150 Dominator carb package (tuned and installed), MSD ignition package, Hippo lifters, composite distributor gear, Cometic head gaskets, ATI balancer, and sheetmetal valve covers, the total package price is $18,340.
As for our little bet--the Twisted screamed on the DTS dyno as it unleashed an astonishing 920 hp at 6,300 rpm and a staggering 809 lb-ft of torque at 5,500 rpm. Once again, SSRE proved bigger is better and we quickly anteed up our one-dollar bet on Scott's 900-plus prediction.
13 The ARP head studs are standard, but the multi-layer Cometic head gaskets are optional
14a The Brodix 383 Head Hunters...
14b...are prepared in-house at SSRE...
14c...The valvesprings are matched specifically to the camshaft.
15 The Brodix 383 Head Hunter heads come fully CNC-ported.
16 The intake runner volume is 383cc while the port flows 434 cfm at 0.700-inch lift, and
NOTE: All runs made with 35 degrees of ignition timing and 93-octane fuel
17 The exhaust port moves 304 cfm at 0.700-inch and 306 cfm at 0.800-inch lift. The stain
18 Comp Cams roller lifters are standard, but our test engine was built with the optional
19 All 598 Twisted engines come with T&D roller rocker arms.
20 The engines are assembled in a clean room and once complete they are moved over to the
21 Scott was quick to point out that our test engine is equipped with the SSRE carburetor
22 Massive 2-inch headers are bolted to the Brodix heads. The engine gulps 93-octane gaso
8090 Auburn Road
Scott Shafiroff Racing Engines
35 Davinci Drive
6747 Whitestone Road
353 Oliver Street
301 Maple P.O. Box 1347