Re: Knock @ 1975 RPMs

["nacelp" <nacelp@bright.net>]

If it's false knock, find the source.
Can be lots of different things, exhuast rattle, serpentine belt,
alt-P/S-A/C bearing noise.   Changing heads meant lots of stuff was apart,
and even little brackets being deleted or installed differently can lead to
silly arse problems that take hours to figure out.  Also, all the wear
pattterns can get changed, and then a noise that wasn't even there pre
modification, springs up.  So thinking a Alt. bearing now can't be the
problem, traps you into not being able to find it if it is.
I'd spend alot of time trying to find the problem, rather then disabling the
KS, especially at that rpm range.  Mechanical fixes would be lossening the
sensor slightly, or possible a more then a tad, remounting it with teflon
tape, remounting it on a short "coupler".
  Maybe with that particular setup it doesn't want much timing there.   I've
seen a calibration take a 12d change relative to the values around it in
timing to take out a "knock" after a cam change.
What lead ya to Isky?.  Ya know anyone running one you can compare notes
with?.  On the EFI stuff unless for all out racing, probably a better idea
to stay with one of the major cam companies, and be conservative rather then
risk, a deep hole (not meant as a flame just for others maybe considering
the same changes)
Grumpy

> After changing heads to a set of 1996 models and installing a longer
> duration Isky cam in my Syclone, I'm getting a 'false knock' between 1975
&
> 2075 RPMs.  Accellerating, steady state or coasting, all the same.  Goes
> right to max retard (18°) in a very short time.  Major fueling changes in
> this area have *no* effect.
> Obviously, this is of electrical or mechanical origin - no wiring changes,
> so must be the sensor 'hearing' something relative to the cam or stiffer
> valve springs that its filter circuits interpret as knock.
> Anybody heard of this?  My first thought is to disable the knock sensor
> below 2100 RPMs ww/ an aftermarket circuit.
> Thanks - Barry


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