Horsepower tips from the pros
By Jeff Huneycutt, Circle Track Magazine
January 3, 2002
1:38 PM EST (1838 GMT)
Sure, working in a Winston Cup engine shop has its disadvantages: long hours, constant pressure to find horsepower, having to throw out your wardrobe every time the team changes sponsors. But there are plusses too, namely an R&D budget to find ways to go ever faster.
So you can have your cake and eat it too, Circle Track polled some of the top minds in the engine-building industry for their tips on making power. Feel free to take credit for these little nuggets of wisdom at the track ... we'll never tell.
SMALLER IS BETTER
To reduce rotating weight, Race Engineering has begun using smaller hardware on the big end of the connecting rods. Connecting-rod bolts are normally three-eighths or seven-sixteenths?three-eighths is a stock diameter and seven-sixteenths is more of a heavy-duty bolt.
By using a bolt with a larger diameter you pick up more beef around the big end of the rod, and you tend to get a stronger piece, but that's at the expense of weight. Bigger hardware means the bolt is heavier as well as the big end of the rod, which has to get bigger to handle the bolt.
We have been using higher-quality steel and reducing the size of the hardware to five-sixteenths. This saves around 12 to 15 grams, depending on the hardware it's replacing. By going to smaller hardware we are saving weight there, as well as reducing the size of the rod. Some guys are running this hardware in engines with up to 650hp, so for a Late Model-type engine, I would say that it's pretty safe.
Bob Koch
President
Race Engineering
THE DEVIL IS IN THE DETAILS
Reliability is a really big key with racing engines, and a lot of that comes down to the details, making sure everything is fitted properly. Obviously, if everything fits together perfectly, there's less parasitic loss in the engine.
Taking the time to make sure everything is nice and clean, everything is deburred and all your clearances are right may cost a bit more money, but it adds horsepower and reliability to your engines, and it's a lot cheaper than replacing an engine that blew up halfway through a race.
Ernie Elliott
Owner
Ernie Elliott Inc.
QUESTION EVERYTHING
Everything on a good race engine has to work in harmony. If you can do something to improve the performance of one component, stop and think about all the things that change can affect. Using smaller journals has already been mentioned, but, if you think about it, the benefits don't just stop with less bearing speed and weight.
Now that your journal and the bearing that surrounds it are both a smaller diameter, you need less oil to keep it properly lubricated. The oil pump can be backed off because now it doesn't have to work as hard to keep oil in the bearings. If the oil pump doesn't have to work as hard, that's more horsepower available at the wheels.
That's a good example of thinking things through on the larger scale, but you can also attack problems on a smaller-than normal scale, too. Take the rocker arms and weight. Reducing the weight on the rocker arms is important, but be careful where the weight reduction comes from.
The pushrod side of the rocker arm is pretty strong because the distance is short from the pushrod end to the fulcrum point. The other side, from the fulcrum point to the spring end, is a lot longer; this is where you have to be careful not to sacrifice stiffness for weight.
If it isn't stiff enough you can get a diving-board effect, which is going to cause you a lot of problems. It's important for the rocker arms to be as light as possible, but they also have to be strong enough to open the valves properly.
Randy Dorton
Chief Engine Builder
Hendrick Motorsports
HONDA SIZE
One good way to free up horsepower is to reduce the journals on your crank. A smaller diameter journal causes less friction as it spins. There are two reasons for this: A smaller journal has less surface area, and because of the reduced diameter, the outside surface of a smaller bearing travels slower than a larger one at the same rpms. This is often referred to as "bearing speed."
There's also a second benefit to smaller journals?less rotating weight. A smaller journal means a weight savings, and you are also reducing the size of the big end of the rod, which gives you a weight savings there too. NASCAR requires a 2.100-inch journal, but if you are in a series that doesn't specify, you might want turn your journals down to what's called "Honda" size (1.888).
I don't know if the bigger advantage is reducing the bearing speed or removing some rotating weight; they go hand in hand. But this is a great way to free up horsepower in two different ways with just one operation.
Bob Koch
THAT SEALS IT
Be aware that different seals you can put in your engines have different amounts of drag. There are quite a few seals in an engine and that all adds up. Evaluate what job you want your seals to do. Normally, seals are only expected to prevent oil from leaking, but in a dry-sump racing engine you want to pull a vacuum, so sometimes a seal has to perform two jobs: hold the oil in and the air out.
Sometimes a seal works better at holding a vacuum if it's put in backwards. So you have to evaluate if your priority is holding in oil or building a strong vacuum. There are different types of seals out there; the rubber stuff is pretty standard, and there are also carbon-type seals that are very good in regards to friction. There are also seals available with a double lip that are very good at controlling both the oil and the air.
With a V-8 racing engine, the difference in seals may be difficult to see on a dyno. The difference may be in terms of tenths or quarters of a horsepower. On a big horsepower engine, a lot of guys will blow that off and say, 'Hey man, I'm looking for five or 10,' but those quarters still add up. All you have to do is pay attention to the details. It's the things like bearing clearances, the rear main seal?those things may only add up to one horsepower, but if that's the first thing I'm putting in the engine, I'll take it.
Randy Dorton
LIGHT IS RIGHT
The engine oils available today are greatly improved over what we had just a few years ago. Everybody used to think you had to have the heavyweight oil for an engine to survive a race. Lighter-weight oils have improved to the point that they can be used dependably.
With the lighter oils you can reduce your pump pressure, which will help you pick up some horsepower. A general rule of thumb used to be you had to have 10 pounds of oil pressure per thousand rpms, but that's kind of an old deal now. If you look at some of the plate engines in Winston Cup, they've reduced the oil pressure down to 40 pounds, and they are running 7,000rpm.
Coated bearings are also a good place to look. If you are going to be running less oil pressure, going with a set of coated bearings can give you a little bit of a cushion.
Nick Ramey
Head Engine Assembler
Robert Yates Racing
THE GAP
Proper ring seal is very important. After you gap your rings, you need to make sure there are no burrs left on the edges, but a lot of guys wind up doing a lot of damage to the rings in that area when they go to debur them. They will chamfer the ends of the ring at the end gap and round the corners considerably. Now imagine what happens when you put that ring in the bore.
It is designed to grow as it heats up and that end gap closes together to seal off the oil. Instead, now you have a nice little path of leakage because the guy has chamfered the end gap so it can't seal up properly. The point is, if there is a burr after gapping your rings, be very careful just to file off the burr and don't chamfer it.
Randy Dorton
LEVEL HEADED
Make sure you have optimal flow through your carburetor. More carburetors than you might think come from the factory with the booster poorly placed in the venturii. The first thing we do at Automotive Specialists is readjust the boosters so they are centered and in line with the venturi. It's easy to level the booster; just place the carburetor on a level surface and use a bubble level on top of the booster to check and make sure it's level too. The benefits of doing this depends on the engine, but if you put the carburetor on a flow bench, it's amazing how much having the boosters centered and level will help airflow.
Jeff Dorton
Vice President
Automotive Specialists
MAKE A PERFECT CIRCLE
Something that often gets missed is proper cylinder roundness. Whether you do it yourself or use a machinist, make sure you have the proper equipment to hone with and use a deck plate. In fact, don't just stop with knowing your machinist uses a deck plate, make sure he is using it correctly. Are they using a head gasket? You should actually use the same type of head gasket that will be used on final engine assembly.
A good hone job is also vital. Make sure whoever is honing your cylinder walls is qualified to do it and then require that he does it exactly like the ring manufacturer specifies.
It's easy to check if your cylinder walls are perfectly round. Bolt the head on the block without the piston or crank in the bottom end. Then use a dial bore gauge from underneath to see just how round the cylinder walls are with the head torqued in place. That's really the cheapest and most accurate way of doing it. We've seen bad piston and ring combinations or other things screwed up in a single cylinder cost four or five horsepower at least. Usually it's the torque that's affected.
A lot of times, if your power is down, something is wrong with the ring, piston or cylinder walls?something in that area. A good racing engine makes the most of its torque at peak cylinder pressure, so that's why a cylinder with a poor seal will affect torque first. So, if you do notice your torque is down, pistons, rings and cylinders are a good place to look first.
If your cylinder walls are not as perfectly round as you would like, using a skinnier ring can actually help you out. A skinny ring conforms to an out-of-round bore better than a thicker ring, so an .043 ring is probably the way to go if you have this problem.
Mark Cronquist
Chief Engine Builder
Joe Gibbs Racing
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