"It used to be that people didn't use sleeves, thinking a sleeved block was a bad block. Today, they're different sleeves. Some of the sleeves they're running in motorsports are 0.0004 inches, and that's not much of a sleeve.
(above and right) Racing-engine blocks can be composed of various materials. Popularchoice
"There are some significant advantages to running sleeves. Many people don't believe in them and say they're a bad addition, [but] many people have had good luck with them. So we're not going to find anyone saying sleeves are perfect, or they're great, or they're junk. There's still a lot of debate over it. Like anything else, you can build winning engines with or without them, but you have to be careful how you handle each side of it.
"As far as friction reduction by using a nikasil coating, I don't know that I have personally seen power gains just by doing the nikasil. In and of itself, it may not be a power gain, but you may be able to build power you couldn't have without it by using other technologies."
Seeking The Right Bore Jenckes found a possible advantage of using sleeves: They come with bigger bores. "Today, people find that particular bore and stroke combinations are very effective," he adds. "Typically, people are running bigger bores and they find that, no matter what the application, a bigger bore may be helpful. I'd certainly say that's the trend in Nextel Cup. Obviously, if you want to make a block last a long time, you can't go to the big bore size immediately. You'll get one rebuild, and then it's junk and you've just spent all this time building this nice block. A sleeve can allow you to go to your optimal bore size. When you have problems, just replace the sleeves.
Boring for cam bearings is a precision step in which modern enginebuilders rely on high-co
"Some teams in Nextel Cup use sleeves, and some don't. In Nextel Cup, the well is deep money wise, but it's not endless. Consider that you can use a smaller number of pistons and crankshafts, and that means less money tied up in crank and piston inventory. Some teams might approach it from that standpoint."
Power From Bore Center Bigger bores have proven to have better results in most cases. "A larger centerline is preferable because it allows you to have a bigger bore," says Jenckes. "A Ford block has an inherent handicap compared to a Chevrolet or the current Dodge because of the smaller centerline. Having more metal there, other than a weight handicap, means it's more stable and it can allow you to run a bigger bore.
"Most racing has some kind of displacement rule. As long as there's not a bore size rule, you're probably better off running a bigger bore, shorter stroke if engine speed is not limited. If you are limited in engine speed for some reason, say an rpm limit, then always going with a bigger bore may not be the way to go, depending on how low the speed is. At higher shaft speeds, bigger bore engines help the cylinder heads work better. In Nextel Cup, 4.185-inch is the biggest bore size you can have. Even if you have 5 inches between bore centers, it doesn't help you other than the fact you've got more metal there to be stable. Then you have to worry about the weight. The trend has been to bigger bore cylinders. GM is working on a new, next generation Nextel Cup engine with a bigger bore center.