Timmy Petty begins work on converting a Dodge Late Model Stock block to an oiling system t
When Dodge first introduced its NASCAR-legal Late Model Stock engine, we showed you the breakdown-part by part-with the help of the famed engine-building shop, Maurice Petty and Associates (Circle Track, Oct. '02). The small shop in Level Cross, North Carolina, had already made its name building Dodge-branded engines for the NASCAR Craftsman Truck Series, as well as the Hooters ProCup Series, and were looking to stake a claim, along with Dodge, at the local racing level, too. At the time, Maurice and his sons, Timmy, Ritchie, and Mark, told us that although the engine is strong, there are a few areas that could be improved upon by a smart engine builder. The engine was still so new, however, that they weren't comfortable saying exactly what those areas were.
Now, the Pettys have had a year to experiment with the engine. They have reliable feedback now that their engines are in several cars in the Southeastern United States. Finally, they agreed to let us take a peek inside and see what's going on in there.
Just like it is with Chevrolets and Fords, oil control is a prime consideration with the Mopar powerplant. The oiling system in the Mopar, however, is different in that it doesn't use the lifters and pushrods to route oil to the rockers and the rest of the valvetrain. Instead, the rockers are mounted on a hollow shaft that feeds the oil. The lifters are oiled off of two galleries that run alongside the cam. Excess oil flows out of the bottom of the bores onto the cam, and eventually back to the oil pan. Part of the problem is that the galleries feeding oil to the lifters are oval and approximately 1/2-inch across at the widest point-entirely too large for racing.
"We felt we were losing a lot of oil control because of the size of those oiling holes," Timmy Petty explains. "Plus, it just isn't as efficient as feeding the oil into the lifter and up through the pushrod. So we came up with a way to oil the rockers like a Chevrolet."
After measuring the correct height with a micrometer, the location for the oil-feed hole t
To do that, the lifter bores are bored out to fit a 1-inch o.d. sleeve. A 0.100-inch hole is cut into the sleeve at the right height so that it will match up with the oil gallery. The 0.100-inch hole allows oil to the lifter, but also serves as a restrictor to limit the amount of oil entering the lifter bores, which keeps the oil pressure up. They use Chevy-style solid lifters that are notched and feed the incoming oil internally to the hollow pushrods. Finally, the old shaft oiling system is eliminated.
Sounds simple, really. And it is, except the Pettys found that when they converted their Dodge engines to this system, too much oil was staying up in the heads, and too little was making its way back to the oil pan. "The holes in the lifter bushings were limiting the amount of oil that made its way through there," Timmy Petty says. "Before, a ton of oil was flowing to the lifters and out the bottom of the bores. We had stopped all of that by changing the way the oil was routed."
The solution is to cut more access holes in the lifter valley for the oil to make its way down into the crank-case. Actually, "holes" might be better described as "craters." MP&A opens up four holes, each nearly large enough to fit your fist through. Additional holes are drilled in the back to further aid oil evacuation when the car is under acceleration. Finally, all the new machine work is chamfered for a clean edge, and every oil gallery is cleaned to make sure no metal particles are hiding inside before the engine is assembled.
"So far this method has worked very well," Timmy Petty says. "I know other motor shops are doing stuff similar to this. They probably are doing certain things differently, but this is the method that works for us. Hopefully, it will work for other people racing Dodges out there, too."