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Discussion Starter #1
I have an 88 Bronco with a 351 V-8 engine. It's making a noise when acceleration. I cannot tell if it's a manifold leak or a valve tapping. Any suggestions where to start?

I don't see any signs of a manifold leak so far. The truck seems to run fine other than the noise it's making. When I'm idleing, you can barely hear it. Under a load (I haul a trailer with mowing equipment), it gets very loud. You can also hear it more on the inside of the cab than you can the outside, when hood is shut. When the hood is open, I cannot tell if it's manifold or tapping at the valves.

I don't know where to start or what to check first.

Thanks, tony
 

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Low on oil? Have you tried spraying carb cleaner around gasket areas?
 

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Discussion Starter #3
88 Bronco

I just changed the oil about 2 weeks ago, so, I know it's good.

It's been doing this for a little while but, seems to get louder and louder each time I drive it.

I did clean out the carb, do you think this could be causing it? Should I change the plugs?
 

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What's the noise sound like?
 

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Discussion Starter #5
88 Bronco

I cannot tell if it's a tapping or a gasket leak at the header. But it gets louder as you give it gas, the sound is similar.

I guess I'd say its more like a loud tapping...
 

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Sounds like exhaust manifold gasket.
 

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Does it sound like its from the bottom of the motor? Louder when its cold or warm??? Know what a rod knock sounds like?
 

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The old mechanic's trick is to put a hose near your ear & move the other end around to locate the noise. An exhaust leak is very clear thru a hose.
 
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