Quote:
Originally Posted by rwd4evr
My 4.5 really falls on it's face after 6000. Not sure if it's Valve float starting or just the cams being setup for low end power with the terrible auto. I'm not even 100% sure its got stock us kjet cams actually. But it just stops revving. Drifting it in third is tough so I really was giving it to it in second.
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Worn valve guides will cost power-especially at high RPM. These heads are notorious for worn valve guides. The heads I just got have wobbly valves as every used Mercedes head I have ever disassembled does. Carbon'ed up intake valves/ports will hurt flow. As you mentioned weak valve springs will prevent the valves from properly sealing along with the worn valve guides. This all hurts high RPM performance.
I did some research and these valve sizes will support 330HP in theory.