In our last article, we looked at the development of the NORAD Toyota 3RZ cylinder head. As expected from Rado and Norwood, the head is a radical piece of equipment designed for maximum horsepower. In this installment, we'll examine the block, rotating assembly and oiling system that's designed to withstand the incredible stress of more than 1400 hp at 10,000 rpm.
As an option in Toyota's Tacoma trucks, the 3RZ is an economical workhorse of an engine. Generating around 150 hp, the 2.7-liter four-cylinder is extremely reliable and trouble-free. But can it be reworked to live in the high-horsepower world of sport compact drag racing?
Bob Norwood believes it can. "The stock 3RZ is an extremely tough little engine. The stock block is cast iron and strong, and the crank is a forged steel piece that needs minimal attention to handle what we're going to throw at it. Everything else gets thrown into the dumpster so what we have is a great starting point for a bulletproof engine," he says.
Chris Rado's 2003 combination featured a Toyota 3RZ that could generate at least 1100 hp. The 2004 version needs to develop at least more than 250 hp, so Norwood is looking at every facet of the engine with an eye on upping the ante.
With the expert crew at LC Engineering assisting, expectations are high. LC Engineering builds all of Chris' engines and knows how to make Toyota engines perform well. "Working with them makes my job much easier. The hands-on experience of the LC crew is a huge asset to our R&D program with the new motor. Our main considerations are strength, weight of the reciprocating assembly and reducing drag," Norwood explains. The engine will be revved much higher than it was designed to do, so the first thing the team looked at was making the block as rigid as possible.
Stiffer Is BetterThe primary benefit of having a solid block assembly is that the intended clearances of the rotating assembly are maintained no matter what stresses are loaded on them. Even a miniscule amount of shifting of the precise alignments of the rotating assembly will result in a catalog of horrors such as crank breakage, bearing failures and cylinder warpage.
The NORAD 3RZ is designed to maintain its structural integrity despite the insane loads that it's forced to bear-the team is looking to generate reliable horsepower. So they first eliminated the water passages in the block. Only coolant will run through the head for added stiffness and the team will create a better sealing area for the head gasket by filling the block. There are many options for block-filler on the market ranging from concrete to purpose-made synthetic fillers, but they add a substantial amount of weight to what's already a substantial casting.
To reduce the overall weight Norwood used structural foam, which is an amazing product. He's used it in blocks in the past with great results. It's light, very rigid and easy to inject into the block casting. "I'd only use it in alcohol motors because it has limited thermal characteristics. A gas engine gets far hotter than an alcohol engine and I'm sure you'd run into problems with shrinkage due to heat. Thankfully, we don't have to worry about that with our engine," he says.
Next, Norwood turned his attention to beefing up the main bearing assembly. The 3RZ uses a two-bolt main bearing cap and the design doesn't allow for conversion to a four-bolt. So Norwood designed an extremely rigid billet-aluminum oil pan incorporating a massive girdle that locates the main bearing caps and prevents any distortion of the bearings under load.
Norwood's ace machinist Tommy Todd carved the pan/girdle from a solid billet of T6 aluminum using a CNC mill. Todd was also instrumental in designing the oil pan drain system that provides a dedicated oil drain for each cylinder. The NORAD oil pan locates by way of extended ARP 190,000-psi studs that pass through the pan and bearing caps to complete an extremely rigid assembly.
The final machine work for the block was carried out by LC Engineering and consists of careful align-boring of the main bearing journals, final finishing of the deck surface and boring/honing of the cylinders. At this stage, the rotating assembly is ready for installation.