the P 5 is an awesome engine, only problem is the pistons and rods are crap in some of them, maybe a bad batch.. i have a P5 and ive shattered 2 pistons and 1 rod, in as many runs,, .. I have replaced the piston and rod with one out of an old hyper 8 port and its working fine, the piston is a smidgen smaller in bore but with a little pinch works great.