If you have a Predator 224, Wildcat 223, or any EC rotating assemblies with the 58mm crankshaft, you may have encountered clearance issues with aftermarket camshafts and rods. (It's worth mentioning that the Predator 224 uses a plastic cam gear and will require an aftermarket camshaft if you run higher than 3600rpms. You can also avoid many of the clearance issues by sending your Wildcat 223 camshaft to your favorite cam grinder for them to put the cam profile you want on it.) If you plan on running a stock engine above stock RPMs, you will have more success with the Wildcat 223.
The stock camshafts for the Predator 224(Plastic Cam Gear) and Wildcat 223(Metal Cam Gear) are 95% identical to your Predator, Tillotson, or other Honda Clone camshaft. Except, they provide enough clearance for their camshaft's compression release. The small engine performance industry, specifically camshaft grinders, doesn't use the Wildcat cams for cores. We don't expect that to change, so that you may have slight fitment issues.
The 58mm crankshaft's counterweights are slightly wider than your typical 54mm or 55mm crankshaft. The standard camshafts have no problem fitting within the crankcase or the cam bosses. However, the cams are slightly wider in areas compared to the stock Wildcat 223 or Predator 224, which causes the camshaft's compression release or EZ-Spin mechanism to hit the crankshaft counterweights.
There are three areas of clearance you need to check if you are using the 58mm crankshaft.
- Camshaft Compression Release
- Camshaft Lobes
- Connecting rod
These steps will also help with any crankshaft clearance in the Honda-Clone engines.
Camshaft Compression Release
The primary issues are related to the camshaft's compression release or EZ-Spin mechanism. There are two styles of compression releases, and each has different areas that need to be ground for fitment. I will refer to each style as Type A and Type B.
One issue we have encountered with the 58mm crankshaft is the compression-release return spring failing. The failure may be due to the spring hitting the crank's counterweight. The easiest solution is to reverse the spring. Usually, the spring's coil is on the moving or outer part of the compression release weights. Removing the spring and attaching it with the coils closer to the cam's core shaft will clear the crankshaft.
Below I will show you where you need to start for clearance-ing, but to check your work put a thin layer of assembly grease on the counterweight of the crankshaft. Turn the engine over with the camshaft installed. If you have a peek-a-boo cover or camshaft clearance cover, those will help keep the camshaft and crankshaft in their proper locations. If you don't, you can cut up an old side cover or take extra steps by mounting your side cover, rotating the engine, and removing it afterward.
Type A Clearance Points
The "Type A" Camshaft requires clearance on the dowels that hold the compression release and spring due to their height. It can be a very tight fit where the top of the dowels is almost entirely removed. The counterweight needs minimal clearance-ing but must be checked in its open position. You can use tape to hold it open as you turn it over in the engine.
Type B Clearance Points
The "Type B" Camshaft also needs the dowel for the spring trimmed down but requires more work to the counterweight. You will also need to check the tab-stops that stick up. You'll need to check them in the open position as they barely hit the counterweight on the crankshaft. Like before, hold it open with tape and turn the engine over.
Clearance-ing the compression release can be a pain. Alternatively, if you plan to use external electric starters, you can remove the compression release by grinding down the dowel outside the cam gear and cam core and then knocking them out with a punch. Or spend a little extra for a billet camshaft.
Using the camshaft without the compression release for any modified engine is in your best interest. Classes such as stock appearing require most of the engine to appear stock, including using the stock recoil start. Work with your tracks and fellow racers to add a stipulation for electric starters. The engines are difficult to start, and the recoils and camshaft also don't hold up.
The compression release will fail at some point. The compression release failing is like a grenade going off in your engine with shrapnel ripping apart your engine. You risk several hundred or thousands of dollars and man-hours to build your engine. And you will increase the risk of injury due to a failed engine.
Camshaft Lobes
One of the more well-known clearance issues with any crankshaft is the lobes on the cam. Camshafts with high lift, big duration, aggressive ramps, or less than typical centerlines can cause interference.
Luckily, the most frequently problematic lobe is the exhaust lobe, the one closest to the gear and the easiest to see. Again, having a peek-a-boo block/cover or camshaft clearance cover will help you keep the camshaft in place for the most accurate information. You may also need a flashlight and a small mirror for checking around the lobe. You can add a thin layer of assembly grease or machinist dye to the lobe to help see where the cam is hitting.
The most common area will be around the shoulder of the crankshaft's crankpin or rod journal. Here you can grind to remove material for the lobes to clear.
I like to start by taking material from this area of the cranks. Be careful not to touch the crank pin journal surface, and thrust radius. Otherwise, you could weaken or ruin your crank.
Grinding on the lobe is also acceptable. Again don't touch the surface, meaning the remaining part of the lobe, or you could cause premature wear, damage, and reduced performance. Come from the side of the globe. If you are a machinist and do this work in a lathe, ensure to leave a radius to prevent stress points on your cuts. Usually, grinding at a slight angle works best.
Recheck your work. Add a layer of assembly grease on the lobe or the area of the crack that the lobes may touch. Turn the engine over and see if the grease was removed.
Connecting Rods
Only EC's Pinnacle Rods are designed specifically for the 58mm crankshafts.
The most common crank pin diameter is 1.180. Every engine except the Predator 212. That means Ducar, Tillotson, Wildcat, Predator 224, Ghost 212, and Honda GX160/200 can use the same rod. The same is true for the flywheels, the Predator 212 flywheels don't work on the 58mm crankshaft. However, the Ghost 212, Ducar 212, Tillotson 212E, and Predator 224 have larger wrist pin diameters. Since many of these parts can be interchanged, it's crucial that you correctly match every component. Otherwise, you'll have loose or tight fitment, and your piston may be too far in the bore losing compression or excessive piston pop-up that causes the piston-to-valve or piston-to-head interference.
For example, the Predator 224 billet stock length rod is part number 8288, made for the stock dish piston. You can also use the Wildcat's 8281 rods with a Wildcat or Hemi Predator Flat Top piston. However, you can't use the Wildcat flat-top piston with the Predator 224 rod because the wrist pin is smaller, and the shorter compression height will reduce compression.
Other Rod manufacturers may have rods that will fit this crank pin, but the extra stroke causes many clearance problems. Many of those rods were initially designed for the 54mm stroke of the clones, and the additional 1mm by the Predator and other 212cc engines' 55mm stroke would only change the rod length by .5mm or .020."
The 56mm crankshaft is right at the limit of rod clearance, depending on the rod and piston combination. However, the 58mm crankshaft is 3-4mm or .120-.160" more stroke than the most common engines, requiring shorter rod lengths of 1.5-2mm or .060-.080".
So far, the issues have yet to be a complete deal-breaker, but the real crux is the dipper and rod cap. Because the extra stroke moves the rod's big end out further, it interferes with the block and, more importantly, the camshaft.
Usually, the rod bolts or dipper may come in contact with the block(especially if you are not using the Wildcat or Tillotson R-Series Blocks), which is relatively minor. In the case of Predator 224, you will need to clear the block as the piston moves from the top of the block to the bore. Since the aftermarket rods use Babbit bearings, so the big end is wider than normal. If you are buying a new engine for modification, I recommend the Wildcat 223, which has the same bore(70mm) and stroke(58m) as Predator 224, but it doesn't have this issue.
The rod cap also makes contact with the middle of the cam's core shaft. Some have grind or machine the center of the cam, usually on billet cores, but I don't recommend doing that. In
addition, you may need to machine or grind the dipper down.
ARC, EC, and any other rod manufacturer explicitly state not to grind or machine connecting rods. You may weaken the structure, cause stress points, or Micro-fracturing, which can cause premature rod failure. EC addressed these issues immediately with their Pinnacle rod designs.
We recommend using our Pinnacle rods, rotating assemblies, kits, and components that help make installation and fitment much easier.
Currently, our combinations work with factory pistons, either the .707 wrist pin(standard honda-clone), .715(Ducar/Tillotson 212E/Ghost212/Predator 224), and 13mm wrist pins(Tillotson 72mm/EC 76mm). There are no 12mm wrist pin rods for the standard Wiseco pistons. You'll need a custom-made piston based around the 13mm and compression height of the Tillotson 72mm piston or EC 76mm Piston.
EC is working to offer more rod and piston combinations with the 58mm crankshaft.
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