The key to any successful buildup is to follow a basic formula. Step one is to decide on a budget, followed by a realistic power goal for the intended application. By realistic, we mean forget about the four-digit power outputs for your daily driver and instead concentrate on what really matters. In most cases, the budget will determine the eventual power output or at least how you go about getting there.
While a brand-new crate motor might be high on the list, the fact is that a wrecking yard buildup might better fit the budget. An honest evaluation is helpful here to get you going on the right track. With a realistic appraisal of the budget and power goals in mind, it is time to start mapping out the components that will help you achieve your goal. Questions that fall into this category include engine family (big- vs. small-block), displacement and even available octane versus compression ratio. You can't build a motor with 12.5:1 compression and hope to run it on 87 octane. Talk with professionals in the industry to help sort out the components that will best suit your needs.
The final step is the assembly procedure, which may include several mock-ups to rectify any clearance issues. But take your time here and you'll be rewarded with a serious performer that can last a lifetime.
For this particular LS1 buildup, engine owner Brian Tooley set his sights on a power goal of 700 hp. While 700 hp is not terribly difficult with forced induction or nitrous, Brian took the road less traveled and decided that the power would come without the aide of a bottle or blower. This 700hp project was an all-motor effort.
Further increasing the degree of difficulty was the fact that said buildup must also produce the desired power on pump gas, as it would find a home in a daily driver that would see some weekend strip action. Now things were starting to get interesting, but apparently Brian had a plan that involved an engine builder's best friend when it comes to power production: displacement. Small displacement would require excessive rpm to reach the 700hp mark. Knowing that engine speed and reliability (to say nothing of expense) go hand in hand, Brian's decision to increase displacement likely also improved reliability.
Stroker motors are all the rage and for good reason. Packaged inside what once was a combination ranging from 4.8 liters up to 6.2 liters (depending on year and application), it can be a real monster. Using an aftermarket block or the Super Deck system from ERL, it is possible to build an LS combination exceeding 500 ci.
With a more realistic budget at his disposal, Brian chose 454 cubes as the final displacement. This was achieved by combining the 4.125-inch bore of a 7.0L (427) LS7 with a massive 4.250-inch stroker crank. The bore was no problem, as Brian chose to stuff the stroker inside an LS7 aluminum block, which already featured the intended bore size. Gressman Powersports was responsible for honing the block to perfection, along with align honing the mains and drilling and tapping the block to receive larger 1/2-inch ARP head studs.
Minor machining was also necessary on the outboard portion of the bottom of each cylinder bore for rod clearance (with the massive 4.250-inch stroker crank). The final fitment issue involved the clearance between the rod bolt and camshaft. With only 0.020-inch, a few seconds on the grinder produced the desired 0.050.
With the block prepped, it was time for the stroker assembly from Wiseco Pistons. It included a 4.250-inch, 4340 forged-steel crank and matching 6.125-inch, H-beam rods from K1 Technologies. Naturally, the kit featured dedicated pistons from Wiseco.
The 4.125-inch forged Wiseco slugs featured a flat-top design, coated skirts, and generous valve reliefs for additional piston-to-valve clearance. The assembly was installed into the awaiting LS7 block using Clevite main bearings and coated rod bearings from Federal Mogul. Further strengthening the bottom end was a set of ARP main studs for the LS7 block. Compression was 11.8:1 with the heads we used, high for sure, but with injection and the proper tuning, definitely streetable on premium.
The long stroke required minor machining of the stock C6 oil pan for windage tray clearance. As is the case with most stroker cranks, it was also necessary to lower the windage tray using head bolt washers. Prior to assembly, the new Federal Mogul oil pump was lightly ported to improve flow.
The final touch was a new custom Comp cam spec'ed out by Engine Power Systems. The hydraulic roller featured 0.660 lift using the factory 1.8-ratio LS7 rockers, along with a 251/266-degree duration split. It was installed using a new set of LS7 hydraulic short-travel roller lifters from Comp. The short-travel lifters make the cam act more like a solid lifter. It won't bleed down at high rpm.
The cylinder heads chosen for this stroker might surprise a few LS enthusiasts. Rather than the high-zoot LS7 or only slightly less zooty LS3 heads, Brian chose a set of Trick Flow GenX 245 cathedral-port heads. Some might dismiss the cathedral-port design in favor of the higher-flowing rectangular ports offered by the LS3 or LS7, but these Trick Flow GenX 245 heads delivered not only some serious peak and average flow numbers (see flow data), but offered impressive torque gains lower in the rev range compared to the LS3 (or LS7 heads). The 245 GenX heads were given the optional nitrous exhaust port work, along with a 50-degree valve job to keep over-scavenging of the cylinders in check during overlap.
Exhaust modifications also included a reduction in valve size from 1.60 inches down to 1.58 inches. Thanks to the precision CNC porting and a 2.100-inch intake valve, the intake ports on the 245 GenX heads flowed 353 cfm at 0.600 lift, while the exhaust ports checked in at 278 cfm.
Minor modifications to the heads included repositioning the rocker stud holes to accept the 1.8-ratio LS7 (exhaust) rockers. Brian also stepped up to the .375-inch diameter chrome-moly pushrods from Comp for this stroker. The Trick Flow Specialty heads were secured to the short-block using 1/2-inch ARP head studs and custom (.066) Cometic MLS gaskets designed for the 4.125 bore.
The finishing touches on the 454 were a new FAST LSXR intake and matching 102mm throttle body. Though impressive right out of the box on a variety of different engine combinations, the FAST intake was disassembled and port-matched to the GenX 245 heads. It is this attention to detail that separates this stroker buildup from your average LS motor. All testing was run with a FAST XFI management system and billet aluminum fuel rail with factory LS3 injectors.
To ensure adequate fuel delivery, the static fuel pressure was pumped up to 65 psi. The 454 stroker also received a Meziere electric water pump, a new set of Denso Irridium spark plugs (IQ27s) and a set of 1-7/8-inch stainless steel headers from American Racing. In truth, the motor would likely make even more peak power with larger 2-inch primaries, but chassis fitment becomes an issue above 1 7/8 inches.
The 454 was treated to a pair of computer-controlled break-in procedures before running in anger. After the break-in and preliminary tuning, the oil was changed to synthetic 5W-30 from Lucas. With 29 degrees of total timing and the air/fuel hovering near 13.0:1, the 454 pumped out peak numbers of 704 hp at 6,400 rpm and 630 lb-ft at 5,300 rpm.
In addition to reaching the magic number, this stroker offered an exceptionally broad torque curve, bettering 600 lb-ft of torque from 4,100 rpm to 6,100 rpm. Torque production never dipped below 570 lb-ft anywhere in the tested rev range. This is is one serious street motor and proof positive that you can make these LS combinations really thump on pump.