Without a doubt, one of the key strengths of the Hughes Engines team is their intimate knowledge of all things valvetrain. Their Chrysler-specific camshaft design work is second to none, but that engineering is only half of the equation. The other portion is on the engine builder to get it all together correctly.
Luckily, Hughes has those details hammered out as well. It all starts with proper preparation:
- Cleaning and lubrication: Double check that the number stamped into the end of the cam matches what you ordered. Lightly wash the camshaft in clean solvent and blow it dry with compressed air. DO NOT BRUSH OR SCRUB A FLAT TAPPET CAM WITH ANYTHING!! With flat tappet camshafts, apply the supplied camshaft break-in lube to the cam lobes including fuel pump lobe, and the lifter bottoms only. NOTE: Roller cams do not require break in lube on the cam. Use light engine oil on the sides of the lifters. Use engine oil or assembly lube on the bearing journals, distributor gear, and pushrod ends. With roller tappet camshafts use a good quality high zinc engine oil to lubricate the camshaft and lifters. Oils have changed and not for the better, please use oil specifically designed for your cam type to protect cam, lifters, and pocket books. THIS IS VERY IMPORTANT!!
- Valve springs: Our camshafts are designed differently and have more lift than other cams of the same size; therefore it is mandatory that you use a spring with the correct amount of open (over the nose) and closed (seat) pressure and also check the valve spring installed height. The enclosed camshaft card will tell you our part number for the springs and the pressures/installed height to use. A minimum of .060” spring travel beyond the maximum lift is required. If you have a problem, we have many different retainers and locks to adjust the installed height — CALL US. When checking true double springs on a tester, be sure to use a retainer or other spacer to simulate the step on the head and/or retainer for the inner spring to duplicate the as installed configuration. If you are using a double spring assembly along with a flat tappet cam, you must break in the camshaft with the outer springs only*. In this case assemble the heads with the outer springs only and follow the regular break-in instructions. After break-in add the inner spring assembly and go racing. Be sure and check the retainer-to-seal clearance. There should be a minimum of .060” of clearance at maximum valve lift.
- Piston-to-valve clearance: Chryslers do not have the piston-to-valve clearance problems that many other engines experience. However, after the valve lifts exceeds .500” and above you must check to be sure. The critical area is not at TDC (top dead center). The critical areas are approximately 10° to 15° before TDC on the exhaust lobe and 10° to 15° after TDC on the intake lobe. We suggest a minimum piston-to-valve clearance of .060” intake and .110” exhaust.
- Check lifter bores: The lifters must slide up and down and turn freely in the bore when lubricated only with WD-40 or similar light oil as a lubricant. You must be able to lift the lifter off of the cam, release it and hear it “thunk” against the cam. If it doesn’t do this, using only its own weight, it is too tight. If the old lifters had to be forced through the bore to remove them, it is quite likely that the lifter bore is damaged and will not allow the lifter to rotate properly. It doesn’t take much to keep them from turning. Fix it or expect problems. Use our Lifter Broaching Tool, P/N 8319, to correct tight or damaged lifter bores.
- Lifters (Tappets): All flat tappet camshafts (both hydraulic and solid) must be installed with new lifters. NO EXCEPTIONS!!! Only roller camshafts can be installed with good used roller lifters.
