Well the end of the road for Project C5X has finally come. As most of you know, this project began almost 2 1/2 years ago, and we have been on a long journey to upgrade Project C5X on a lot of different levels. That journey included a Mid America Motorworks (Performance Choice) interior upgrade, Pfadt sway bars and coilovers, an American Car Craft stainless steel accessories package, a Baer brake upgrade, basic engine add-ons including Dynatech headers, Mid America Motorworks exhaust and air intake, an Elite Engineering tunnel plate, and an MTI shifter install. Almost all of our installs, and 100 percent of our dyno work, was done by Next Level Performance in Altamonte Springs, Florida, and Geoff Skorupa and crew have done a superb job! We covered lots of editorial ground, but what we really want to do now is to bring this project to a close by installing the last go-fast parts on the car and produce some real horsepower on the dyno.
Before we can really say goodbye, we need to cover the installation of our new LS1X World Warhawk heads and custom grind C4orce Comp Cams hydraulic roller camshaft and valvetrain. To backtrack just a little, most Corvette owners realize that the LS1 is the perfect candidate for making power. The LS engine has been one of the most easily modified engines ever built and with every new LS generation, Chevrolet keeps improving the breathing ability, thus making it that much easier to make easy gains with very little effort. The original LS1 engine is still residing in Project C5X and we always knew we could make some good power with our almost-stock LS1 engine.. so early on, we decided the most prudent use of our time and energy would be to build the stock engine we already had instead of swapping in a brand new LS stroker.
Prior to the head and cam install, we installed a new VMax Motorsports throttle body and we wanted to see what kind of horsepower it would mean to a near-stock Corvette. After we got that install nailed down and dyno'd at about 7 RWHP, the head and cam upgrade was up next. A head and cam upgrade is one of the simplest and most productive upgrades for any car but especially so for the LS1.
There are lots of choices out there today for this type of swap. We wanted to try to find the cheapest horsepower for the money, so we looked very hard at all the aftermarket components available for the LS engine. After some consideration, we decided to try a set of the LS1X World Warhawk heads and a custom grind C4orce Comp Cams hydraulic roller camshaft and valvetrain. Pete Incaudo, owner of VMax Motorsports, worked on the development side for the LS1X World Warhawk heads, so that made our cylinder head choice a little easier. The World Warhawk heads we used had the 72cc combustion chambers and feature 235cc intake runners similar in design to the cathedral port of the LS1 and LS6. We would have liked to have used the 64cc version with a smaller intake runner, but it was not currently available at the time of this build.
Pete also had to angle mill these stock castings to arrive at an optimum 62cc combustion chamber that yielded a 10.5:1- 11:1 compression ratio, which is fine for the street. The combustion chamber in these heads is fully CNC machined. On the exhaust side, Pete hand ported and polished the short side radius and intake runner entry to enhance flow through the intake without enlarging the port volume. On the intake side, the port received minor work on the short side radius and floor with enough material removed to eliminate the casting lines. As Pete was working on the heads and checking for pushrod clearance issues, he found that there was interference with the casting. He then had to hand grind the pushrod opening and unfortunately, since the casting was too thin in that area, to get enough clearance he broke through all the intake port walls. This had to be repaired by welding a new wall area around the pushrod opening to alleviate the problem.
The World Warhawk LS1X heads are set up for 2.08/1.60 valves and in this install, Manley Performance valves were used. A Comp Cams LS1 Dual Valve Spring Kit with titanium retainers and their machined steel valve locks were also used. We also used Comp Cams Hi-Tech pushrods, and we decided to try their killer Ultra-Gold CNC-aluminum 1.72 Ratio GEN III Rocker Arms for this build. Due to the fact that the stock LS1 pushrods will not work with these heads, you need to make sure you measure for correct pushrod length because of the difference of the rocker arm rail height of the World heads, and because we had to angle mill these heads to get the compression correct.
Along with our custom Comp Cams camshaft, we also decided to use Comp Cams GEN III High Energy OE -Style Hydraulic Roller lifters. We also tapped Comp for one of their GEN III Adjustable Timing Gear Sets that features a pre-stretched heat-treated double roller chain and has a 3-keyway crank sprocket for an additional 4-degree incremental adjustability. Comp also sent us their GEN III Crankshaft Socket, Degree Wheel, Cam Degree Tool and TDC Stop to use during the build. These tools are invaluable when building an engine of this caliber. Dimmit Chevrolet of Clearwater, Florida, also provided all of the bolts, gaskets and even a GM PF46 Oil Filter needed for the rebuild.
As we said previously, we decided to do a custom C4orce grind camshaft to take full advantage of all of our parameters. This camshaft is one of several C4orce camshafts that we have designed over the last couple of years that Comp Cams has built for us. We will talk about the specifics of each of those cams in a future issue of Corvette Fever. What we can say at this point is that this particular camshaft uses a larger lobe separation number than most for better idle quality. One thing to always remember when choosing a cam profile is not to go overboard if the car is to be driven (especially daily like Project C5X is) on the street. The LS1 engine is so responsive to small changes in cam profiles that you really don't have to get radical with your upgrades. After we had the engine completely torn down, and the original heads and cam removed and cleaned, we then began the installation of the new Comp cam. With our new Comp Cams GEN III Adjustable Timing Gear Set (with their 3-keyway crank sprocket for an additional 4-degree incremental adjustability) and new GEN III Crankshaft Socket, Degree Wheel, Cam Degree Tool and TDC Stop, Geoff Skorupa of NLP then degreed the camshaft in. He recommends that all custom camshaft installations should be degreed per the manufacturers' cam card specs. Now we were ready for the cylinder head install.
We knew from the beginning we would have to modify the new World heads to fit this particular application and part of that was angle milling the stock castings to arrive at a 10.5:1- 11:1 compression ratio. As we mentioned before, due to pushrod clearance issues, material had to be taken out from the casting which opened up into the intake ports. This had to be repaired by welding a new wall area around the pushrod opening to alleviate the problem and was our second modification. Upon installation of the cylinder heads to the block, we ran into some more modification issues. Everything looked good up until the installation of the Comp Cams Ultra-Gold GEN III Rocker Arms. We couldn't even tighten down the rocker arms because the top valve cover rail was interfering with the rocker. We then tried installing the stock rocker arms and quickly found that we still had the same top valve cover rail interference issue. There was just no way that the stock rockers would fit on the World heads. The only alternative we had was to hand grind the valve cover rail area on the cylinder head above each rocker arm to get enough clearance for proper rotation of the rocker arm.
Once all the rocker arms were installed and properly adjusted, the next issue we found was during the installation of the valve covers. The stock valve cover bolts bottomed out into the casting before the valve covers were tight, so we had to decrease the length of the valve cover bolts to properly tension the valve covers. After installing the headers and trying to install the coolant sensor into the driver's side head, we realized the sensor hole in the head had been drilled too close to the exhaust header flange, making it necessary to hand grind the header flange for clearance of the installation of the sensor. While installing the intake manifold, we then found interference between the bottom of the intake and the heads, thus not allowing the intake ports to seal properly. Out came the hand grinder again, while we removed material from the bottom of the intake for proper fit and seal of the manifold. The intake manifold bolts also had to be shortened for proper installation of the manifold. After this problem was rectified, the rest of the engine was buttoned back up and we headed for the dyno.
Strapping Project C4orce on the dyno for the last time was bittersweet. After putting an initial computer program together for the modifications we installed, we started tuning for drivability and making sure everything was running properly mechanically. After all the prelims were out of the way, we started turning the wick up and began tuning for power. It is very important to correctly tune a combination like this for reliability, drivability and power. With Geoff's years of experience in tuning LS engines and having gone through proper tuning classes over the years from prominent OEM calibrators, we correctly dialed in the computer system for years of fun and reliable driving times as the new owner, Roger Less, will quickly attest to. The final dyno numbers on Project C5X came out to be 411 RWHP, which was 116 more horsepower than stock. The tune in the car was so consistent that after the Roger took delivery of the car in Colorado, he had it tested and tweaked for his altitude change and his tuner came up with the same 411 RWHP figure. Right on!
On a closing note and with a tear in his eye...to Project C5X from Geoff Skorupa, God Bless and God Speed!