what _IS_ a good cruise A:F ??

[dzorde]

Hmm, someone that seems to know a lot about the 350 (good).  Mabye you can
help, my 350 is set up with 4 deg static advance and it uses the Accel blue
advance springs in a HEI dizzy.  Yet, it still sounds like a machine gun if
you go wot when engine temp is as low as 85deg cel.  I have thought of
running a 170F or 160F thermostat to run cooler (180F fitted) but haven't
had time yet (doesn't ping when semi-warm 75C).  The next move is also to do
a compression test to see what its like, it had normal flat top pistons put
in when I built it (but who knows how much the machine shop took of the iron
heads).  Anyway, what sort of compression PSI am I looking for ?  By, the
way I run pump leaded (95oct, have thought of trying BP100). I also run
standard plugs at 0.05" (could they be too hot ?, too big a gap ?).  Where
do I start ?

Dan     dzorde at geocities.com
 
>There are a few factors that can lead to pre-iginition and detonation.
>Hot spots in the combustion chamber, too much ignition advance, shitty
>gas, too much compression, too lean a mixture combined with one of the
>above... the list goes on. And of course it can be a combination of any
>or all of the above too.
>
>You need to nail down a table of limitations for your engine and operate
>inside that table. Most of the time, you can start by using well known
>limits for your engine that have been discovered by trial and error by
>possibly hundreds of thousands of experimentors. Take a 350 chev for
>example. If you want to run on swamp water, er, I mean pump gas, and you
>have iron heads, you are looking at 9:1 compression and typically a max
>total advance of about 38degrees. If you are within these lines and you
>get detonation or pre-ignition, I would start to look at mixture, spark
>plug heat range, cylinder head temp, etc. Of course there are always
>more variables, the above is just an example for one engine type.
>
>The best single device to tell you what's going on inside is an EGT
>guage. That combined with measurements from everything else will give
>you plenty enough clues as to what's going on.
>
>As a side note, my Z-28 has an Accel HEI (yuck) on it with the
>adjustable vacuum advance and I have several spring sets for setting the
>curve. It took me quite a while to get the curve just right so it
>wouldn't ping at about 3000 rpm while still maintaining the total
>advance I needed up high. If you're rattling, your hurting the engine.
>Take it from someone that's ventilated more than one piston trying to
>get that last couple hp.
>
>-j-
>