[Supras] Whipping noise

[Rockey Fox]

so it sounds more mechanical than electrical? From the frequency I would have have guessed electrical like maybe an arcing spark plug wire but then but then the disappearance after warm up wouldn't make sense.
What about one of your pistons slapping more when the plug fires (every other stroke) which goes away after reaching operating temperature?

Rockey 91T - also has brief piston slap on cold start, usually after two or more days sitting idle which is rare since no backup vehicle currently.

----- Original Message ----
From: "berniek at technicaldevelop.com" <berniek at technicaldevelop.com>
To: "Supras at supras.com" <Supras at supras.com>
Sent: Monday, February 4, 2008 6:28:19 PM
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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