Last month we outlined our plan to build a NASCAR Late Model Stock-legal Ford engine utilizing the Blue Oval's new Boss 351 block and N351 cylinder heads. If you remember, the block is an all-new design intended to replace several different blocks in the Ford Racing Performance Parts inventory. The Boss 351 block wasn't designed expressly for NASCAR Late Model Stock racing, but it likely will be the best option for the racing class moving forward.
On the other hand, the N351 cast-iron cylinder heads aren't technically new, but they are a new casting that replaces the old, worn-out tooling. And they are produced specifically for this class of racing. NASCAR has approved the new casting because Ford has proven that it doesn't offer a power advantage over the older head, but there are changes intended to make the new casting better in terms of consistency, improving durability, and reducing the steps necessary between taking the heads out of the box and bolting them up. In theory, these new heads should make the engine builder's life a little easier than before.
Our plan is to put that theory to the test by actually building a race engine to see if the new components will contribute in a meaningful way toward winning races. To add legitimacy to this plan, brothers Charlie and Robert Long of Charlie's Automotive will be handling the build. Charlie's Automotive is one of the premiere engine builders in NASCAR Late Model Stock racing and has a very competitive Ford package. For this build we went with Charlie's preferred recipe for cooking up some Blue Oval horsepower, and the guys even shared a few of their tricks for eeking out power on these engines.
In the first installment of this series we took an in-depth look at the new block and heads. This month we start screwing parts together and complete the short-block. Stay tuned as we complete the long-block next month and (hopefully) bolt up the accessories.
1. Engine builder Robert Long...
1. Engine builder Robert Long checks the main bearing clearances before beginning the build. All the bearings in this engine build are coated pieces provided
by CV Products. It isn't necessary to line hone the new Boss 351 block, unlike the older race block Charlie's Automotive used (which came 0.002 to 0.003 undersized on the mains).
2. The polished crank is from...
2. The polished crank is from Crower. This Crower design uses a larger snout to prevent cracking in that area. Long added a good bit of Mallory metal (you
can see the round slugs in the top counterweight) in order to be able to turn the counterweights even smaller. Balancing a crank in this manner can be a bit tricky because Long refuses to drill lightening holes in the ends of the counterweights because they can cause extra windage.
3. Robert Long gently sets...
3. Robert Long gently sets the crank into place. The Boss 351 uses a larger 2.75-inch Cleveland size main bearing journal, so Robert looks for a clearance on each of the journals between 0.0026- and 0.0030-inch.
4. With the main caps in place,...
4. With the main caps in place, crank thrust is checked to make sure it is between 0.007- and 0.018-inch.
5. The rods are Crower I-beams...
5. The rods are Crower I-beams that are 6.250 long with a 2.225 main journal and 0.927 pin end. If you are sharp, you've probably already noticed a lot of Chevy dimensions in there-and you are right. Charlie's actually uses a Chevy rod and piston package in its Ford engines.
6. A look at the pistons installed...
6. A look at the pistons installed on the connecting rods. These pistons do not use a gas port, which has become popular among engine builders for oil
control. Charlie says that's because it's so important to free up all available horsepower in a Late Model Stock engine, he is willing to burn a little oil in order to reduce the drag the rings create against the cylinder bore.
7. The pistons are custom...
7. The pistons are custom forgings from Wiseco. They actually start out as Chevrolet slugs designed for LS motors, but Charlie Long likes these pistons
because of the strong boxed design on the underside and the narrow pin bosses. They are a bit heavier than the pistons many other Late Model engine builders
use at 410 grams, but Charlie believes they are worth it. One important note here is that boxed pistons do require a couple thousandths more piston-to-wall
clearance than traditional designs, and the siamesed cylinders of the Ford block also require a bit more clearance, so piston-to-wall clearance with a build like this should be on the large side.
8. The ring package is a Wiseco...
8. The ring package is a Wiseco GFX set that utilizes a 1.2mm top ring, a 1.2mm napier style second ring, and a 3mm oil ring.
9. The Crower camshaft is...
9. The Crower camshaft is a solid flat tappet as per Late Model Stock rules. It's ground with 252 degrees of duration on the intake lobes and 259 degrees on the exhaust with a lobe separation of 107 degrees and a 103-degree intake centerline. At the valves it should produce 0.561 lift on the intakes and 0.559 on the exhaust. This may not sound very radical for an all-out race cam, but Charlie likes to run his engines at very high rpm levels and says the cam grind is a balance between getting the most air into the chambers quickly and keeping the valves under control at high rpm levels.