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Racing Engine Technology - What's Next?
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Racing Engine Technology - What's Next?
Doug Herbert Performance Opens Up Its Nationwide Series Engine Program To Show Us The Top-Level Engine Technology That Will Be Making Its Way To Saturday Night Racing In The Coming Years
By Jeff Huneycutt, Photography by Jeff Huneycutt
April 01, 2011
Oil control is a big deal in these motors, and we're not just talking about oil pressure. Because race teams depend so much on aero, they tape up as much of the grille as possible, so controlling the oil temperature is also important. One thing engine builders have found is that opening up the connecting rod side clearance can help keep the oil temps cooler without harming the bearings. But the connecting rod position must still be controlled, so they do it by bringing in the pin towers so that there are only a few thousandths of an inch between the small end of the rod and the cheeks of the piston's pin towers. This not only helps guide the connecting rod, but it also shortens the piston pin which can lower the overall reciprocating weight.
Oil control is a big deal in these motors, and we're not just talking about oil pressure.
Piston rings are a big source of friction inside a race engine, and Cup and Nationwide engine builders have gone to great lengths to find the right ring package that has minimal friction while also still providing adequate oil control for a weekend of racing. Viccaro says DHP says the top ring it's currently using is a very high-tech piece of steel. It's 0.119-inch thick and anodized to keep it from welding itself to the piston's ring lands. It's also held to very tight tolerances and, unfortunately, runs approximately $600 for a set. A napier-style second ring is used to help maintain oil control but has very little tension to minimize drag as it travels up and down the cylinder bore.
Piston rings are a big source of friction inside a race engine, and Cup and Nationwide eng
With the RO7 block, the water jackets are completely redesigned compared to the classic small-block to help even out the temps from one cylinder to the next. Water flows into the cylinder head from the large hole at the 5 o'clock position at each cylinder. It then flows across the top of the combustion chambers before exiting the engine. The two large rectangular holes at the top of each cylinder also expose the water jackets, but the amount of water that can come out of these holes is restricted by the head gaskets. Also notice the extra holes for head studs. This not only helps improve head sealing but the holes also extend deeper into the block before the threads start to minimize cylinder bore distortion when the heads are torqued into place.
With the RO7 block, the water jackets are completely redesigned compared to the classic sm
Although this block is upside down, you can still see the extreme size of the cam tunnel. Engineers have figured out that the extreme spring pressures engine builders are running to help maintain high-rpm valve control can actually cause the camshaft to flex along its length. When this happens it throws off the critical valve timing events-when the valves open and close-which hurts power. To stiffen up the valvetrain, the RO7 is cast with an enlarged, and raised, cam tunnel that will accept 60mm camshafts. If you look closely, you'll also notice one big difference between this and the classic small-block: There is no provision for a standard fuel pump.
Although this block is upside down, you can still see the extreme size of the cam tunnel.
Notice how the crankcase volume is divided equally by the main journal webbing on the RO7 block. Because this is a dry-sump engine, this design is important because it helps equalize the amount of vacuum pulling on the underside of each piston. In this photo, you can also see the provisions for piston oilers built right into the casting. Each piston gets two oilers so that the cooling effect of the oil will be approximately the same on both sides of the pin. Finally, the steel main caps use four parallel studs and aren't splayed like classic small blocks with four-bolt main caps. This block was designed specifically to use four-bolt mains, and straightening the holes probably creates room in the block for other things-like the galleries for those pin oilers.
Notice how the crankcase volume is divided equally by the main journal webbing on the RO7
If it weren't for the valvecovers, at first glance you might mistake this for a Ford because of the distributor up front. But there's a very good reason for this type of Chevrolet blasphemy. In the classic setup with the distributor at the back of the block, the distributor is driven by the camshaft at the rear, while the camshaft is driven by the timing chain at the front. This means that any flex in the camshaft also affects the ignition timing. By moving the distributor to the front of the block right next to the timing chain, any chance of this happening is practically eliminated.
If it weren't for the valvecovers, at first glance you might mistake this for a Ford becau
This is an SB2 rocker design, but it's still very interesting. Shaft-mounted rocker arms offer much greater stability than stud-mounted rockers, but they can be difficult to adjust. Usually, it means adding or removing shims underneath the rocker stands to adjust the height of the rocker arms. This setup that Viccaro showed us uses a cam system to raise or lower the rockers within the mounting blocks.
This is an SB2 rocker design, but it's still very interesting. Shaft-mounted rocker arms o
Reducing the diameter of the valve stem is very effective because it cuts weight on the short side of the rocker arm in the valvetrain. And a fraction of an ounce cut from the rocker pivot to the seat of the valve is more valuable from the rocker pivot to the lifter. To that end, most Nationwide engines are now using titanium valves with 6mm stems. To deal with unleaded race fuel-which will also include 15 percent ethanol next season-engine builders are also going with coated valves. Viccaro says that three coatings that are currently working best are titanium nitride, chromium nitride, and DLC, or "Diamond Like Carbon." These two valves are both coated, but you can only see the DLC coating on the exhaust valve on the left.
Reducing the diameter of the valve stem is very effective because it cuts weight on the sh
Because of the super-thin valve stem diameters, there isn't enough width for the roller tip of the rocker arm to move across. To fix this, engine builders use lash caps which sit on top of the valve stem and provide a greater surface area. These caps are also used, obviously enough, to adjust valve lash, and so it now becomes important to keep a variety on hand.
Because of the super-thin valve stem diameters, there isn't enough width for the roller ti
Here's a shot of two different shaft-mount rocker arms. Viccaro says most Nationwide engines use a fairly extreme ratio between 1.8:1 and 2.0:1 in order to take some stress off of the camshaft. You can also see that there are no lash adjusters (the reason for the lash caps in the previous photo) to further cut weight.
Here's a shot of two different shaft-mount rocker arms. Viccaro says most Nationwide engin
Because extra weight on the pushrod side of the valvetrain isn't as critical, teams are using larger (and heavier) pushrods to further stiffen the valvetrain. This is a 1/2-inch pushrod that tapers to 7/16 to help with clearance in the cylinder head. It also has a thick wall to further strengthen it at 0.180-inch. To keep from having to maintain a vast inventory of different length pushrods, DHP uses these pushrods with press-on ends. Once Viccaro determines the exact length he needs, he cuts down the end of the pushrod in a lathe and then presses on the ball end.
Because extra weight on the pushrod side of the valvetrain isn't as critical, teams are us
Like the valves, the retainers and locks are also titanium. Titanium retainers used to be notorious for having an extremely short service life, but Viccaro says that new coatings have significantly increased the durability of titanium retainers. This retainer has a coating that gives it a slightly rough, gray surface. Also notice that the locks have only a single, small bead to clamp onto the valve stem. When the valve stem is only 6 mm in diameter, you can't have a very deep locking groove. Because of this, Viccaro says it's critical that you keep your valvetrain under control.
Like the valves, the retainers and locks are also titanium. Titanium retainers used to be
Nationwide engine builders are flooding the valve covers with oil to reduce both damaging harmonic vibrations and heat in the valvesprings. But spring oilers are still necessary for startup. The new RO7 valve covers integrate the spring oilers right into the casting. Oil enters the gallery from a hole in the cylinder head. After entering the valve cover (upper corner) it travels under pressure to the spring oiler gallery which has fittings to direct a fine stream of oil to each valvespring.
Nationwide engine builders are flooding the valve covers with oil to reduce both damaging
In the foreground is an SB2 camshaft, and the cam in the background is for the new RO7. Notice that the RO7 cam has an extra cam journal for support (six compared to the SB2's five). The journals are also much narrower to reduce friction. You can also see that the advanced overall design of the RO7 is more compact from the shorter camshaft, despite the fact that the block has a greater bore spacing (4.500 inches compared to the SB2's 4.400).
In the foreground is an SB2 camshaft, and the cam in the background is for the new RO7. No
Doug Herbert Performance
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By Jeff Huneycutt
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