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HPR and GSpeed at it again, with a 442 CID LS3 C5 Road Racer
Completed HPR 442 short block
The HPR 442 is another one of our exclusive builds that Erik has designed to be the largest stock LS3 (no sleeving or aftermarket blocks). Working hand in hand with Wiseco we have developed the piston to fit within the confines of the OEM sleeves with the bigger crankshaft stroke.
For this particular build we are doing a dry sump, road race version for our friends at GSpeed and their customer's C5.
After years of hard work on track being force fed by a supercharger and already one rebuild on the LS6 he wanted to remove some weight from the car, stop the summer over heating issues and maintain similar (or maybe more) power. Easiest way to do that? Go bigger!!
As mentioned before, this engine starts life as a new GM LS3 cylinder block and slightly honed 0.005 over to accept our new forged pistons. Clearancing is done to the block to accept the new larger stroke crankshaft, finally surfaced, washed and ARP studs installed ready for the new balanced rotating assembly.
assembled bottom end.
Since this engine will be using a aftermarket dry sump pan and pump, it uses the std length post on the crank, and 24x wheel for the C5 ECU.
Trick Flow 255 cylinder heads were chosen for this build as a budget friendly cylinder head with a number of good features such as light valves, solid castings, and strong flow numbers for the size hyd. roller cam we would be using.
Trick Flow 255 GenX heads
CNC chambers
Lightweight stainless intake vavles
Lightweight stainless exhaust valves
CNC ported intake ports
CNC ported exhaust ports
Working with Billy Godbold at Comp Cams we chose to remove the springs that Trick Flow sends the heads with and switched to a stable cam lobe profile that would allow the use of Comp's new 7230 conical single beehive spring. These allow for up to 0.660 lift when setup right
Removing the dual TFS springs and Ti retainers
Setting up install height for the new Comp Springs
Installing Comp's 7230 conical spring. Oddly enough these offer almost a 60lb rate increase over the dual springs they replace. With the Tool Steel retainers, weight was dropped from 12 gram for the dual Ti to just 7 grams for these tool steel ones.
To further stabilize the valve train we went with a ti bar Morel lifter which also features a slightly larger 0.750 wheel vs the OE 0.700 wheel. Lifter diameter remains 0.842. By using the larger wheel you can start to decrease stress at the point of contact of the camshaft. One of the reasons you see high RPM engines using wheels larger than 1.000"
Lifters about to be pre-oiled before install with Motul break in oil.
close up of the 0.750" wheel
Custom ground cam from Comp Cam's using a very stable lobe, and their new MSE finishing process, again added to help improve valvetrain life.
Camshaft going in
You can here Billy speak more about this finish below.
Assembled heads going on to be secured with ARP hardware.
Checking valve rocker tip wear and pushrod measurements. In this case we will be using a thick walled 3/8 custom pushrod.
You have probably heard us speak a lot about valve train stability in our builds, including this one. While it is not using super high end components but every piece that was used, is designed and picked for as much rigidity that can be had. Using a very stable cam lobe may forgo some HP numbers but lap after lap, year after year the cam is not going to beat up the valve train and will help keep the car on track. Using stable springs, thick walled pushrods will minimize deflection making sure we maintain as much lift as we can at the valve and reduce valve train noise and hopefully bounce in the RPM ranges we are planning to see this engine live (7500 and under).
Dailey Engineering billet oil pan, ATI balancer, and 3 stage pump.
Lastly, this engine is being finished off with a 3 stage dry sump pan and pump that was spec'd by GSpeed for the customer's car to keep it supplied with oil at all times, even under high G load corners. A large capacity Peterson tank will be installed with oil coolers as well.
Dropped off and ready to be installed.
Last edited by HP RESEARCH; 04-20-2018 at 06:06 PM.
Do you do anything to the rockers (trunion upgrade) or run them stock?
This one had BTR upgraded trunions, but other than that, it was a stock rocker arm.
the other thing I didn't show in this one was the 0.130 wall 3/8" pushrods. Given the room in the head, we try and run as large of a diameter as we can fit to keep the pushrod from flexing. In this case the head didn't have the room (at least not without further machine work) so a heavier wall was used.
I did much the same path...pulled my supercharger and went back to the LS6 NA. The heat, the mass, the way it made the car feel, while awesome in ways, just wasn't the purity I wanted. I've refocused on big grip, cooling and coming up with an NA plan.
This build and the other big cube monsters you guys are putting together...it just is
As for how they are finished out from that point, all depends on what you would like to do as there are a TON of options when it comes to heads, valvetrain..... Something like this with the dry sump (no tank or lines), you would be around $14-15k. So figure a little more than a new crate LS7 that will make more power and have a better oiling system with all forged internals.
do you guys have any issues with longetivity going with a 4.25" crank?
Not at all. Erik has been doing these larger stroke engines now for well over 15 years without issues. Over that time he has done a lot of piston work to make sure they stay very stable in the bores, which helps a lot.
What sort of power did this end up making? What manifold? Can you spin this to 7500 with like a FAST Medium Runner and have it hold on past 7K?
Wonder how the torque curve compares to the 468...
We did do a little intake testing with GSpeed on the setup using a med runner FAST compared to the stock ported LS3 intake on it.
Ported LS3 intake (red) vs Med runner FAST (blue) HPR 442
As well can be expected the shorter runners lost some low end and began to pickup in the mid to upper RPM range and allowed it to carry more HP in the higher RPM ranges. It is interesting to note it didn't gain a a lot more power PEAK over the OE runner which could be due to the smaller valves and smaller cam in this build vs the bigger cams and heads on the 468's using a LS7 style head.
These could very well benefit from a reworked TFS LS3 head (these are stock out of the box TFS heads) or going to a small bore LS7 head but you loose the runner length options with the LS7 intake manifolds currently.
Last edited by HP RESEARCH; 02-04-2019 at 09:20 AM.
04-20-2018, 12:20 PM
HPR and GSpeed at it again, with a 442 CID LS3 C5 Road Racer
