I recently have had a new crate motor installed in my truck. I'm having issues with it losing power and a loud popping sound coming from the engine. This is my second crate motor and the first motor had the same issues. It runs fine until it warms up then as i'm driving there is a loss of power and i have to accelerate through it then it passes......until i decelaerate and it starts running rough and has loud pops coming from the engine. I replaced the ICM, new CAT, new plugs and wires, the distributor is new.... just about everything under the hood is new. Any ideas what this may be? I've read a lot of posts that has the same issues but nothing has worked. Also when this issue occurs i hear valves rattling like crazy and there is the popping. I need some help on diagnosing this problem! 1994 F150 302 5.0

 

I would suspect incorrect rocker arm to valve stem clearance(I think the only way to change that is different length push rods) or some bad valve lifters.

Did you buy the crate motor through the party that installed it? What about warranty?

 

Isnt a crate motor basicly a drop in and go??? Short of adding oil, gas, coolant. Maybe adding the front brackets and maybe a water pump??????

If your having problems with it,,, like massey said who installed it??? Take it back to them!!!!!!! I wouldnt even begin to guess whats wrong with,,, being a crate engine.