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Re: Valve clatter

>To: MHLIGGINS@aol.com
>From: "Doyt W. Echelberger" <Doyt@NWOhio.com>
>Subject: Re: Valve clatter
>In-Reply-To: <4087769@nwohio.nwonline.net>
>In operating my 87 5kcstq, I've been noticing a sound much like what you
describe. But I wasn't ready to call it valve clatter because I'm just not
that experienced as a diagnostician. I did come up with a list of suspected
conditions that I have read about on this list: Pre-ignition knock, faulty
vacuum valve, distributor noise, main seal leak, WGFV buzzing, wastegate
seal leak. Now maybe valve clatter.
>The noise might easily be just what you say, valve clatter. It comes on
when I accelerate heavily, and when I hear it the acceleration usually
starts to drop off like the fuel pressure was being cut back. Since it
started, I've been much less prone to doing heavy acceleration. As the
weather cooled off recently, the condition has gotten less troublesome but
isn't gone away totally.
>When I accelerate less heavily, the noise develops when the engine is
starting to level off at the end of the gear, just before I would normally
shift into the next gear, and if I let up just a little on the accelerator
when I hear the sound, the rattle stops. I am talking about RPMs of maybe
3000-4000 here, not radical stuff at all.
>I have a mechanical dialable wastegate valve that bypasses the WGFV to
control the wastegate, and a few days after the rattle started, I was
running about 10 pounds boost above atmospheric.That's about 1.7 bar. I
backed it down to about seven pounds (1.5+ bar) and the rattle appeared
less frequently and didn't cause as much drop off of acceleration.....more
noise than effect. In addition to the mechanical WGFV bypass, my ECU is
also slightly modified by a small resistor between posts 1 and 10. This
moves the spark considerably beyond factory specs, and this is why I
thought the noise was a pre-ignition knock or distributor rattle.
>I've been going to take the car to my mechanic for his opinion, but just
haven't got around to it yet. Sheer procrastination.
>Thanks for the post on this topic, as it shifted my thinking somewhat.
Please keep the thread going as you get replies and private posts....I need
all the help I can get.
>Doyt Echelberger
>86 4kq
>87 5kcstq
>At 04:13 PM 9/17/98 EDT, you wrote:
>>	I've continued to dink around to resolve an apparent problem with the
'91 10v
>>turbo engine I installed in my '87 5KTQ.  Primary symptom was that the boost
>>went away at times, especially when it was warm.  I've checked most of the
>>"normal stuff" as suggested by several q-listers.  Car is in basically stock
>>(ECU and waste gate) condition.  The only changes are that the engine is
>>years newer (thus slightly higher compression) and I also used the K-24 from
>>the donor car.
>>	Now that the outside temps are going down a bit, I've run the car some with
>>the windows down and the a/c off.  What I'm finding is not what I wanted to
>>find.  Under heavy acceleration the valves rattle like they're about to come
>>out.  It's beginning to appear that the low mileage engine (77K) I bought
>>been trashed.  But, just in case I missed something (always a possibility),
>>please refresh my memory as to what could have been installed incorrectly to
>>cause the valves to clatter.
>>	I would normally suspect timing, but the ECU controls that.  Any
comments or
>>suggestions appreciated.  But at the moment I'm fearing the worst, might
>>to use this head on the old engine with high miles -- at least it didn't
>>	Thanks.
>>	--ml