Like virtually every other long-term vehicle project with which we've been involved, Project C4orce has had its share of detours, about-faces, and wrong turns. Frankly, it's surprising that this project has proceeded so smoothly, considering that we're not simply installing existing products, we're also developing new ones. (Which are or will be available for sale through a number of sources.) We're not trying to reinvent the wheel or develop high-tech methods for addressing square peg/round hole interfaces, we're developing components that either don't exist or don't meet our specific requirements or performance criteria.
As an example, motor mount adapters are required to install an LSx engine in any chassis not originally designed to accommodate one. Whereas a conventional Gen II or earlier small-block has three bolt holes through which each mount is attached, a Gen III or Gen IV block has four. A number of companies offer adapter plates, so we ordered a set with the intention of installing them, test fitting the engine in the chassis, and moving on to the next item on our "to do" list.
Then a detour popped up. The adapters we ordered bolted to the block and accepted the C4 motor mounts with no problem, but the machine work looked like something done during the first week of a high school shop class, and the adapters didn't position the block properly in the chassis. So we developed our own C4orce design adapter plates. Then Trey Hanson installed them, set the engine back in the chassis, and this time, everything fit properly. In theory, these adapter plates should successfully marry any LSx engine to any chassis that originally housed a Gen I or II small-block, or Gen 6 or earlier big-block. We're testing a number of non-C4 installations, so we'll soon have a list of engine/chassis combinations that are or aren't compatible. (Currently, these adapters are available through Speed Hound Performance and Vmax Motorsports.)
Another "problem" associated with installing an LSx engine in a C4 chassis was lack of headers. Although opinions vary as to their suitability, LSx exhaust manifolds that will fit a C4 chassis do exist. Stock manifolds are obviously less expensive than a set of long-tube headers, but they would have imposed a significant performance restriction. Unless you're in the business, building a set of headers is, at the very least, challenging, so developing our own didn't seem like a viable proposition. Fortunately, we didn't have to search for other options because Dave and Chris Wiehle of Melrose Headers had become aware of the C4orce project and offered to develop a set of LSx-specific C4 headers. Melrose's current product line includes both C5/C6 and C4 headers, so the obvious starting point for configuring a set to fit C4orce was simply a matter of modifying the company's existing L98/LT1 headers to fit an LS1/LS2/LS6 header flange.
Nothing is ever quite that easy, so Melrose sent a partially welded set, along with some loose pipes for us to test fit and adjust as necessary. Ironically, "Mr. Clean" (Trey Hanson) did most of the "dirty work" of trial fitting and modifying, and then we sent our modified sample back to Melrose so they could make the required adjustments. We subsequently received a production prototype, installed them, and confirmed they fit correctly.
The next challenge was to find the rest of the pieces needed to complete the exhaust system. We want to keep Project C4orce emissions compliant, which means the exhaust system will include catalytic converters. That being the case, we didn't have to think twice before making the next phone call to Random Technology.
We've used Random's converters in just about every other Corvette Fever project (in which emissions compliance was a consideration) and have always had excellent results. Random already offers a stainless-steel, mandrel-bent, 3-inch, dual converter/x pipe system for header-equipped C4s, so building a system for Project C4orce involved making alterations to an existing product, rather than building something completely new. In this case, the task was a bit simpler because the existing system is modular, consisting of an "X-back" portion and separately available front pipes that connect the "X" to various types of headers. Consequently, all we needed to complete the exhaust system was a set of front pipes to fit the Melrose LSx/C4 headers and a pair of mufflers (which are not included in the Random converter/x-pipe assembly).
According to Random Tech's Clay Ingram, "Our C4 system is a true dual exhaust with an "X" that replaces the single exhaust on '84-'91 models. We figured most people with C4s already had performance mufflers, so the Random system ends at the muffler inlet and that allows you to run just about any muffler you want."
As you might expect, there are a few other components that need to be changed before an LSx engine will drop into a C4 chassis. One is the oil pan. The truck pan (that came with our 5.3-liter engine) is too deep and must be replaced. An F-body oil pan is ideal and reasonably easy to find. We were fortunate enough to find someone who wanted to trade an F-body pan and oil pump pick-up for our truck parts.
While we were at it, we also traded water pumps. The primary differences between the truck and F-body/Corvette water pumps are length and water outlet position. If you're on a tight budget and can't find a suitable replacement, you can make a truck pump work, but it's a lot easier if you install an F-body or Corvette pump
While we continued to grapple with the changes required to accomplish the automotive equivalent of installing a square peg in a round hole, Pete Incaudo and Anthony Spensieri of VMax Motorsports were reworking the engine's cylinder heads. Pete has been porting cylinder heads for more years than either one of us care to remember (dating back to the '70s, when his Cylinder Heads America company supplied small-block cylinder heads to the majority of winning and record-setting drag racers). Pete was also first to recognize the potential of CNC-porting for street applications, and he has an unrivaled understanding of the way air flows through a cylinder head. That understanding enables him to develop port designs that deliver optimum flow characteristics while meeting specific cost limitations.
Considering our $15,000 total budget, cost considerations aren't taken lightly. Certainly, a pair of fully CNC-ported heads will provide higher air flow capacity and, ultimately, more horsepower, but they'll also cost a good bit more. Our challenge to Pete was to come up with a maximum power/minimum cost combination. And that's precisely what he did.
Pete's budget-conscious modifications of our 5.3-liter head castings incorporated hand porting and blending the valve bowl area and short turn radius (which is the section of the port that has the greatest influence on flow). After the port work was completed, Anthony attacked the castings with his array of seat, guide, and valve machines. Through his extensive background in race engine head and block preparation, Anthony has developed a number of machining procedures that assure maximum precision. In developing race-winning components for classes in which allowable engine modifications are limited, he found that power output and durability are increased when valve seats and guides are machined to specific precision and consistency standards. In years past, that type of work meant relatively high costs because of the time involved. But with the new high-tech machinery that has become available during the past few years, that's no longer the case because operations that formerly required multiple steps can now be completed in a single step. That makes them ideal for limited-budget performance street engines.
Combined with our special "C4orce-grind" camshaft that was ground by Comp Cams, the modified heads should pump up the horsepower of our $700 5.3-liter LSx to about 335-or about 90 more than the original 5.7-liter old-school TPI engine. Sound good? It does to us, and we'll have more details next month.