[Supras] Whipping noise

[berniek at technicaldevelop.com]

Chris:


    Yup.  That and a sticky valve were my first thoughts, which is why I 
mentioned the damper bolt in my first message.  But a loose pulley 
should not stop making noise when warm.  The thought of it being a 
sticky valve is beginning to occur to me more and more.  Running rich 
under boost produces soot, which (because of the pressure differential 
from the exhaust port to the cam cover might push open the garter spring 
seal on the stem at 18 PSI boost) might make its way into stem to guide 
clearance.  Any thoughts? 


    Bernie


Chris Smyczek wrote:
> Ever check torque on that crank bolt? Shake it?  If not to torque and the
> balancer is moving torsionally against the key..Your key will be shrapnel,
> crank shaft and pulley..?
>
> -----Original Message-----
> From: supras-bounces at supras.com [mailto:supras-bounces at supras.com]On
> Behalf Of berniek at technicaldevelop.com
> Sent: Monday, February 04, 2008 5:28 PM
> To: Supras at supras.com
> Subject: [Supras] Whipping noise
>
>
> Hmm..  The group has not seemed this dead in a long time.  Is the server
> down?
>
>
> Anyway, my '91 (550cc, Lex, Walbro, upgraded IC, 3" exhaust) makes a
> very loud repetitive cracking sound from someplace near the front of the
> engine on cold startup.  It sounds almost like an amplified arc, or
> cracking of a whip when I listen under the hood.  Most times it occurs
> at random, but if I speed up the idle slightly, it occurs at times in
> sync with what appears to be every other revolution of the engine (i.e.,
> 4 stroke style).  The sound must be outside the engine, since it sounds
> like a cracking whip.  It appeared after about 600 miles on a refreshed
> JDM.  One thing I need to do is check the harmonic balancer bolt.  I did
> not tighten it all the way to the spec, as the pipe used on the breaker
> bar began to bend.  Could it be the balancer moving torsionally on the
> crankshaft against the woodruff key?  Strangely, once warmed up it is
> fine.  The stock pistons are fitted loose, and I do have cold piston
> slap as well, expected.  But this noise is far more "in your face"
> regarding high frequency content, not muffled or damped by the block walls.
>
>
> BernieK
>
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