Project Mudslinger: Shoehorn, Please!

We’ve all heard big things often come in small packages. Yes, we know it’s a cliché about as old and tired as Grandma’s mint-green Buick grocery-getter, but there is a kernel of truth to it. In the case of the Project Mudslinger, every cubic centimeter of engine displacement means one pound toward the car’s total weight. You can overstroke a four cylinder to come up with gobs of thrust, but it does no good if the weight penalty makes it impossible for you to turn in the corners. Needless to say, we are looking for big power in a small package.

Race Engineering and Johnson’s Machine Shop have been wrestling with this problem for years, and the two companies have teamed up to produce some pretty vicious four-bangers (see our stroked four cylinder buildup, “Supersize It!,” in the Feb. 2001 issue, or go to www.circletrack.com). They agreed to assist us in our quest for speed and even to let Circle Track follow along to show you exactly what’s going on inside our little black powerplant.

Race Engineering specializes in the short-block, and Johnson’s Machine builds the heads, complete with overhead cam. Race Engineering normally ships its short-blocks assembled, but for our project Tim Yates, Johnson’s head engine builder, is handling all the engine assembly at Johnson’s shop in South Carolina. Our block is a 2.3 liter that originally lived in either a Ford Mustang or Ranger pickup. It has been bored .030 inches over, align honed and machined to zero deck the pistons. Total displacement will be 2,340cc. Rules state the crank also has to be a stock piece, but that’s about all. Race Engineering takes advantage of that by shaving approximately three pounds off the counterweights. Three pounds may not sound like much at first, but it’s a ton in terms of rotating weight and drastically improves acceleration. After balancing, our crank now weighs in at a svelte 28 pounds. Both the block and crank are baked at 700 degrees in a special oven and shot-peened, both to strengthen the metal and thoroughly clean it after years of road use.

Before our Race Engineering Pro rods and Wiseco pistons are installed, everything is prefitted, complete with bearings, and thoroughly checked for proper clearances. Yates says Johnson’s and Race Engineering recommend .0025-.0028 clearance between the main bearings and the crank and also .007 endplay.

Once everything checks out, final assembly can begin on our short block. Our 5.7-inch rods are fitted to a special set of Wiseco pistons. Because the wristpin hole extends into the oil groove a spacer is supplied to support the oil ring. The first ring is gapped to .012, and the second is gapped to .010. Main caps are bolted in at 85 pounds, while the rod bolts are torqued to 50—both with 30 weight motor oil.

The bottom end is buttoned up with an oil-pump snorkel and pan from C-Line Engineering. C-Line makes some fantastic products for Late Model race cars and recently put all its engineering tricks into this oil pan for Ford four-cylinder engines. It’s deep with a wide sump to move oil away from the crank and has more gates than a compound filled with militant separatists. The custom snorkel has a wide mouth and is cut to pull oil from the very bottom of the pan. Richard Johnson, owner of Johnson’s Machine Shop, estimates this pan adds seven horsepower over the stock unit on a dyno. He’s sure the actual number is even higher when the oil is sloshing around in the pan during a race.

Rules for our Mod Four class require the head be stock, but they do allow the head to be converted from hydraulic to solid lifters. Since this is an overhead cam engine, there is a lot of power to be found here. In addition to converting to solid lifters, we are also allowed to cut inside the bowl on a diameter smaller than the valve seats and perpendicular to the valve stem. We can also blend on any angle up to ¾ of an inch from the top of the valve seats.

But before Yates does any of that, he strengthens the head by welding metal straps to the top of the cam towers. If these straps are not welded into place, the extra stresses caused by racing can crack the towers. After Yates finishes grinding his welds smooth, you can hardly tell anything has been done.

To convert from hydraulic to solid lifters, Johnson’s has lifter bore sleeves and adjuster studs specially made to its specifications. The sleeves are designed with .003 crush to really lock them in place. Richard has found that this works better than the more standard knurled inserts. The adjuster studs are also longer than the ones many engine builders use to keep more threads in the insert after adjusting valve lash. Conversion from hydraulic to solid also requires shaving .350 off the top of each of the bores.

Next, the head moves over to the valve seat machine for a series of cuts. First, Yates opens up the valve guides so new bronze guide sleeves can be inserted. Then the valve seats are cut with a tool that does all three angles at once. Yates is careful to cut no more than necessary; keeping the cut shallow minimizes the depth of the combustion chamber. Finally, the interior of the bowl and the side of the combustion chamber next to the valve are cleaned up to improve airflow.

Unlike many Late Model series, our Mod Four rules have no requirement for minimum combustion chamber size. This allows Johnson to pick the compression he feels the engine needs and deck the head until he gets it. The goal for our engine is 12.3:1, which translates to 42cc combustion chambers. Yates has to take a total of .170 off the head on an angle to get there (on this head every .007 cut equals one cubic centimeter removed from combustion chamber).

Finally, it’s time for assembly. Yates triple-checks the stainless steel valves against the seats then installs the cam. Johnson has his cams ground to his own specs, and the CIA is more lenient with its secrets than Johnson about his cams, so don’t even bother asking. All we know is lift for both the intake and exhaust is .500. Yates grinds the valve stems so they lift .500 with no lash, then sets the adjuster studs to .010 lash in the intake and .012 on the exhaust before locking everything down. We are using single valvesprings with a height of 1.625 to 1.650 inches and have 250 pounds of pressure compressed.

Johnson’s Machine completed the package with a set of Race Engineering pulleys and belts that are about as light as they come. Firepower comes via a distributor and coil from Mel’s Ignition. (You can read more about Mel’s innovations for four-cylinder engines in “A Simpler Spark” in the July 2001 Circle Track.) We are also using a racing-specific water pump from MPR Inc., which has a roller bearing and a backing plate over the impeller to prevent cavitation.

We’re pretty happy with our little beast of a powerplant. Johnson recommends we run it all the way up between 7,800 and 8,000rpm, which is possible thanks to the overhead valve design. We plan to feed everything with a Keith Dorton Series, Holley two-barrel carburetor (PN 80583-1). This 500cfm carb is based on Holley’s 4412 model with some really nice tweaks to make it competitive right out of the box with a high-end piece from a carburetor tuner. Now all we have to do is get in gear with the car and see how it all works together—easier said than done!

Part I: In the Beginning There Was...Junk

Part II: All Caged In

Part III: Shoehorn, Please!

Part IV: Toil And Trouble

Part V: What Do You Mean, Start Over?