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On my 67 Mustang GT with a 390, the engine runs smooth at idle and normal driving conditions. During hard accelleration and higher rpm, the power tapers off quickly, and the engine gets very rattley. It sounds like valve train noise. It is not timing, it will just barely ping so it should be right on. The oil pressure is good- ie I have a guage that reads normal, the pressure is not going down. Could it be valve float, or lifters collapsing?? I know this is hard to diagnose like this, but any ideas??
 

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You're right, it's hard to diagnose without being there, but I once knew of a 390 that would float out at just over 4500 RPM. And it did it consistently. I'm not sure if there was something inherent to the engine, or that one just wasn't set up right. By the way, the car was only a few years old, and had never been apart at the time.

Lots of folks here know more about 390's than I, but your float problem rang a bell, so thought I would share it with you.
 
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Here is something to consider. I had a 410 built for my 69 Mach.(Just a longer stroke 390). The guy here in Louisville is noted for bieng the best at ford big-blocks. HOWEVER,,,,,i knew there was a problem with noise,,,,at higher rpm's started ratlling like a diesel.I finally MADE him take the damn engine apart,,,and low and behold he had put the wrong wrist pins in it.He was very embarrased.He kept telling me that it was valve train noise due to adjustable rockers and the mild cam i had in it.I knew it was something else and i was right,,,,so think about that possibility too.
 
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