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Discussion Starter #1
I did a search and there was no real answers. my 351 has a rattle type noise almost like an exhaust leak sound to it, only when engine is at a cruise type situation, not under load or decel. now I have 2 cars with this engine and only one makes this noise. and I have hedman headers on this car. could the noise im hearing be the valves im hearing and I cant hear it the other car because it has the heavy stock cast manifolds? when in park under the hood and reved up I cant hear the noise do to everything else going on under there.:( any ideas? thanks
Shane
 

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Use and engine stethescope or another decive that will allow you to focus your hearing and magnify it so that you can first determine if its top end, bottom end, or outside the engine, and then further pinpoint its location. Id first elimate an exhaust leak and something on the pulley system as that will be the easiest to figure out. Then go from there.
 

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info

Doc here:pimp:

What type / year car is this? Does it have a Cat (s)...?

Sounds almost like a Cat or muffler heat shield coming loose...

Or maybe a flexplate cover?

Valves would be a higher pitch Clatter and be present throughout all ranges of RPM. not just one speed.

Doc:pimp:
 

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Discussion Starter #4 (Edited)
the stethascope is a good idea, i will try that, the noise is a very constant steady noise so I dont think that it is a shield. it is a 1970 mercury montego so theres no cat under it. just headers, pipe and flowmasters. ok so I just checked and the noise seems to be coming from my carb. with a stick I can hear the noise most from the middle area of my intake. it sounds like lifters to me, but it doesnt mis or backfire at all. it runs super smooth. could it be clearance on my valves/pushrods? and if so how do you check it, whats the clearance? I am using sae30, should I use a heavier oil or lighter? or do you think its something completely different? thanks
Shane
 

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Baffle

Doc here:pimp:

Is it possible that those rockers could be hitting an oil breather baffle on the valve cover? Some of those aftermarket items don't play so awfully swell together...

Also, If the rockers were too tight, It would run awful...like missing, and backfires...

Doc
 
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