Exotic Performance Plus: High Performance Auto Parts and Services

Randy Hargraves and his 851 rwhp '02 Z06 HP Turbo'd Twin Turbo Corvette
This update from: 05/17/2008

Randy Hargraves and his 851 rwhp '02 Z06 HP Turbo'd Twin Turbo Corvette.

Our original intention was to add better cylinder heads and a camshaft with a lopey idle to this otherwise stock engine, along with a twin turbo package that Randy had ordered from HP Performance. Randy opted for the optional and larger 57mm turbo's, in case he ever wanted to go crazy with his Corvette. By looking at HP Performance's website, and by talking to the people at HP Performance, this seemed like a pretty straight forward turbo install. Boy, were we in for a rude awakening...

In this picture you can see the partially torn down Corvette waiting on the parts from HP Performance. The fenders and the front nose have to come off to install the turbo kit.

The turbo parts have arrived, well, not all of them. We've been told from HP Performance that we'll be getting the rest of the kit shortly.

HP Performance sends their fabricated parts to Jet Hot Performance to get coated. They do look nice!

Still waiting on the other parts to arrive from HP Performance. As the weeks go by, we're starting to feel like we are getting lied to.

While we were waiting on the rest of the parts from HP Performance, we added a much shorter throw shifter from B&M. Shifting this car will now be so much easier.

The cylinder heads showed up that Randy had ordered from Felber Racing, located in Florida. Randy had Felber CNC and polish a set of LQ9 cylinder heads, and they do look awesome!

You can see that these heads look very good, and they should really make this Corvette run very well.

So what is going on here? Randy wisely decided that while we were still waiting on parts from HP Performance, we might as well as better rods and pistons. We have found the stock pistons to handle 500 rwhp on our Mustang Chassis Dyno, which is a lot of power, but we have a feeling this engine is going to be waaay past that amount. The ringlands on the stock pistons are what goes on these engines, and we have seen it happen many times when the horsepower goes past the 500 rwhp mark.

This piston is not from Randy's engine, but I thought I would show you what these pistons look like when the ringland cracks. If this happens and is caught in time, no damage to the block will occur. Cylinder head damage is very common when a piece of the pistons lodges between the piston and the cylinder head combustion chamber, making it a good excuse to upgrade your cylinder heads as well...

We installed a Comp camshaft that we had specially ground. The spec's are 232/240 at .050 .595/.608 lift with a 115 lope separation. This cam should work very well in a forced induction application, and yet it will still give the engine a lopey idle.

Calles Compstar connecting rods and Diamond forged pistons along with Total Seal rings were added to this engine. The stock crankshaft has been proven to handle well over 900 hp, so we chose to keep the stock crank, although we had it polished and balanced. In this picture you can see that we added ARP head studs, which will help seal the head gaskets much better.

In these pictures you can see the HP Performance tubular headers and turbo components installed.

The engine has been bolted back to the front suspension in this picture.

You can see Brent lowering the Corvette back over the front suspension/engine combo in this picture. This is the safest way to install the engine back into one of these cars.

It is starting to look more like a Corvette again. You can see the HP Performance intercooler in this picture. HP Performance does not provide a way to mount this intercooler, and we also found out they have no instruction manual for this Corvette twin turbo kit! We were promised some pictures to help figure out where they intended on some of the components to go, but so far we have not received them.

Some more of the turbo parts have come in from HP Performance, and we were able to mount the turbos to the chassis. The intercooler plumbing runs through both wheelwells from the intercooler to both turbos. We are still waiting on these pieces which are made out of carbon fiber, from HP Performance.

While we are waiting on the carbon fiber parts from HP Performance, Randy had us install a wheelwell tub kit in his Corvette, so that wider rear tires could be installed. We picked the wheelwell tub kit up over at Lingenfelter's.

The first thing to do is to remove the old wheelwell panels and wheelwell tubs from the Corvette, which requires cutting them out with a Sawsall. This is a messy job that will leave you itchy and glad that you don't do it for a full time job!

You can also see in this photo that we relocated the battery to the right rear, which was necessary to install the turbo kit.

In these two photos you can see the new wider wheelwell tubs that are supplied to allow wider tires to be used. Trimming in necessary to make the new wheelwell tubs fit tightly.

The new wheelwell panels are fitted and screwed into place.

The finished job looks pretty much like it left GM with the wider wheelwells, once the parts are painted to match the rest of the trunk compartment.

These are the wheels and tires that are going to be installed on the back of this Corvette, giving the car a full twelve inches of rubber on the ground!

Randy (middle) stopped by from his home in Nashville, Tenn. Here he is shown here talking to Brent and Tony.

Here you can see the air filter attached to the passenger side turbo, along with the necessary heat shielding.

You can see the intercooler tubing going up to the fender here. We are still waiting on the carbon fiber pieces from HP Performance!

While we were at it we had the transmission rebuilt by Rodney at RPM Transmissions. Rodney knows all the tricks to these transmissions, and rebuilds them to withstand a lot of abuse.

HP Performance sent us some of their molds that they were trying to make their carbon fibre pieces with. They suggested that we could use them on this Corvette to get the car completed, as they were not having any success creating them.

Hmm, as soon as we looked at this piece it looked like it wasn't going to clear the hood...

The quality of these molds wasn't exactly what we had in mind for this instasllation. We're not sure if they would even hold up to the boost.

The seams on these mold pieces just don't look like they would handle much boost, but we may use them to get the car tuned in.

We ended up getting a piece from another source to use between the mass air and the intercooler. There was no way the part supplied from HP Performance was going to clear the hood.

This definately looks much more professional!

We painted and installed the HP Performance supplied turbos to intercooler molds for now, so that we could get Randy's Corvette up and running. Some instructions on all of this would of been helpful, but we got it all figured out...

The Corvette is back out seeing the light of day! We wanted to make sure all the oil lines were bone dry before we put the fenders and front nose back on the car. Speaking of lines, it would of been nice if this turbo kit had come with the required fittings. Luckily we have approx 50k worth of Earl's fittings in stock!

Brent is thinking, when will it all end! ...

The rear of this Vette now looks more like a supercar, with it's wall to wall tires.

We will be needing to take the front fenders back off and do some adjustments with the turbos, as they are forcing the front fenders out.

The HP Performance kit does not offer any protection to the turbos and related parts from road debris at the wheelwells, at least to our knowledge. Since we don't have any instructions and we didn't get any extra parts, we're assuming we will have to build our own.

We made sheetmetal panels to block off the turbos from road debris, and they also served to reinforce the bottom of the fenders behind the wheelwells.

Here is a good picture of how the panels we made will protect the turbo parts behind the wheelwell.

We found one fitting that was cracked and leaking, which figures. It didn't leak until the fenders were back on! We temporarily sealed it with some RTV, until we got a new fitting.

We welded brackets to the intercooler to mount it to the chassis. The right side bracket can be seen in the picture.

The front air dam has been reinstalled, and the intercooler plumbing is up and well out of the way.

HP Performance had sent us a big ugly red Summit racing battery box to use for the relocation of the battery! This red box is not what they show on their website, and this Corvette certainly deserved better! We cut the lower portion of the battery box apart and modified it to work for this application. We purchased some carpeting and constructed a cover for the battery.

It's time to tune on our Mustang Chassis Dyno, using our LS1edit.

The car is making 790 rwhp and 750 ft lbs of torque with only 14 pounds of boost! With this much power it is nearly impossible to keep the rear tires from spinning on the dyno. We had the tie down straps really cinched down tight, which still wasn't enough. We resorted to having John and Chip take a ride in the trunk, plus we had Tony inside the car in the rear hatch. Surprisingly, this still didn't cure the problem. You can actually hear the tires break loose in the video in 4th gear, when the rpm's got up past 4500 rpm.
Randy is going to continue to try and get the carbon fibre pieces from HP Performance for the intercooler tubing. If this fails, he said he would more than likely make them out of aluminum.
Once Randy gets use to the power that his Corvette now possesses, we'll more than likely be upping the boost for another dose of horsepower.

1/5/06 Randy called and said his car went spinning down the track to a 11.30 at 142 mph, and the track officials mentioned to him that he was letting off before the finish line!!!!

Video of this car in action:

Twin Turbo Corvette

5/17/08 Update:

Randy brought his Z06 back to us to have us install a larger fuel system in it, so we could up the boost. We hadn't seen Randy or his Z06 for years, so it was nice to have them back, and it is nice to see the 'lil 346 was still running strong! This time around Randy's Z06 got tuned with our EFI Live software, instead of the LS1edit we use to use. That tells you just how long it has been since we built this car!

Once again we had a tough time getting traction on the dyno. We used extra straps to draw the rear tires down on the dyno rollers and Randy's 335's would still break loose. We did manage to get 851 rwhp, had the tires not broken loose and unloaded the turbo's, we are sure we would of seen a lot more power.

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