Ford 150 v-8 f-injected, 302eng. at idle the enging has not noise , but when going into passing gear at about 45-50 mph it sounds like I have an exhaust leak, but it started out as there was a valve pecking. not heard at idle or in park and running motor from idle to about 3500-4000 or so rpms. when pulling a hill noise comes back like exhaust leak and hearing valve noise through exhaust. a mechanic it could be a piece of carbon in the cylinder and advised me to get some "sea foam" (additive) and put in gas tank and it would help burn this out. I did. did not work. he also mentioned the valve in back of the motor connecting the 2 heads together that it may be leaking or the either lines to this valve may have a hole in it. I once had a car that a roller lifter collasped and it made a noise simular but in the ford truck this noise is not heard at idle or in park and reving engine, only when pulling hill or going into passing gear. I need suggestions or probable cause. the lifter I mentioned the noise was heard even at idle. this noise I hear sounds like a valve pecking and it is heard through an exhaust leak (either a hole in the manifold or I lost a stud or a bolt has fallen out, I can tell it is in the motor while driving.

 

Are you sure it's not pinging?

Billy

 

How about your air pump? Is it and all its plumbing still intact?

 

I would look at the emmisions pipeing. The EGR valve is only open at certian times and that might be why you only hear it under load. If it is anything like the emmisions on my 89 351 there are a lot of places that you can have a leek. And they can be hard to find. I bought my truck new and had to have all the emmision stuff replaced three times in the first 50,000. Found out that that was because the thermostat was bad from the factory and the engine never got up to tempture thus rotting out the check valves and pipes on the emisions system because at lo temp it condensates and does not carry out the accitic gases.

Just a thaught