348 What causes engine top end noise (tapping) - Ferrari Life
 
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post #1 of 8 Old 01-19-2015, 05:26 PM Thread Starter
 
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What causes engine top end noise (tapping)

Other than valve lash what can cause what sounds like valve tapping ? The sound is similar on both sides and does not change whether cold or hot.

I ask the question because I am confident the valve clearances are set correctly.

I started the engine for the first time after a DIY major and rebuild of the heads including seals, guides, and springs. The head work was performed by a machine shop and Fcar mechanic both with over 20 years experience working exclusively on exotics, mostly Ferraris.

The engine starts and runs well, holds oil pressure above 70 when hot at idle, temp also OK. Does not smoke on startup or while running. Using 10-40 Castrol oil. I do get a CEL on the 5/8 side after approx. 10 minutes.

So assuming this work described above is correct what else could cause this problem. I'm wondering if the air/fuel ratio or the compensation valve under the plenum might cause the engine to run lean and cause gas knock which I am interpreting as valve noise. I did put in fresh gas to rule this out.

I appreciate your thought on things to check before I remove the valve covers to check the lash.

Thanks,

Brewman
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post #2 of 8 Old 01-20-2015, 04:34 AM
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If you can get some readings from a vacuum gauge, ignition scope and 5 gas analyzer, it'd be a lot easier to rule out possibilities. The two most common things that could be confused with lifter tick would be a faulty fuel injector and a spark plug wire arching off the head inside the well. Depending on severity, a small exhaust leak at the header could also be mistaken for lifter tap. I suggest starting by checking those possibilities.


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post #3 of 8 Old 01-20-2015, 05:27 AM
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Was the noise there before the head work was done?

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post #4 of 8 Old 01-20-2015, 04:39 PM
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This is a 348 right?

Assuming it is if poss you could use a scope and listen to each exhaust. From the info given i agree could be sparkplug or injector. I am not as familiar with a 348 and its sound.
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post #5 of 8 Old 01-20-2015, 05:17 PM Thread Starter
 
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Quote:
Originally Posted by David @ FluentInFerrari View Post
Was the noise there before the head work was done?
David,

The noise was not present before the head work.
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post #6 of 8 Old 01-20-2015, 05:43 PM
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As mentioned above I've seen(heard) many exhaust leaks sound exactly like a valve tap. Usually right where the exhaust meets the head.

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post #7 of 8 Old 01-21-2015, 09:14 AM
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Kevin's point regarding the exhaust gaskets is a good one....
Other Idea:
-Did you remember to reset the "checking clearances" after you went through the cam timing process (presuming that you used that procedure)?

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post #8 of 8 Old 01-21-2015, 02:11 PM Thread Starter
 
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David,

I guess not since ai do not know what " checking clearance" is. I did verify the lash after timing was set.

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