INSTALLING NEW 12.5 PISTON ON 2003 PREDATOR, DOES THE VAVLE CLEARANCE NEED TO BE CHECKED, MOST PEOPLE SAY NO. PLUS SHOULD I RUN REGULAR OIL IN IT TO SEAT THE RINGS BETTER OR SYNTHETIC? DID ANYONE HONE THE CYLINDER WALLS FIRST, PLUS DOES THE 2003 PREDATOR HAVE A NACASIL COATING OR SLEEVE?? THANKS FOR ANY INPUT.

 

the only thing I can say is you only have 1 chance at the timing! that valves should be fine on adjusting but it is a good idea to do often. the piston does help alot on power! good luck

 

Make sure you torqe the head bolts just like the book says. The 12.5 made a difference in my predator. But I tell ya lighten the fly wheel after you put the piston in. The fly wheel made the most noticeble power power gain. Be safe

 

To do it right you shouild definetly check the valve clearance it wil be alot cheaper in the long run we have seen new stk. machines that needed to be re-set. , the stk. pred cyls have a steel sleeve in them and yes you should run a hone through it and coat the rings/piston/cyl. walls as well.

 

how do you properly check the vavle spring clearance? thanks

 

Use modeling clay in the valve reliefs of the piston with at little light oil on the surface. Don't put in on too thick. Assemble everything and rotate the engine slowly. Disassemble the head and cut the clay in the middle of the valve relief and measure the height of the clay at the lowest point. Anything less than .100' may require deeper valve reliefs machined into the piston or advancing or retarding the cam for more clearance. You're probably safe with the stock cam unless you've had the head milled or using a thinner head gasket. It's always wise to check it when running a more agressive camshaft. You could also check with the piston manufacturer to see if the piston has deeper valve reliefs than the stock piston. Many aftermarket forged pistons will have deeper reliefs for cams with more agressive lift and duration than stock.