Try checking the centrifugal advance with an adjustable timing light.
Stretched centrifugal advance springs will result in max advance as far too
low and rpm which will cause pinking/pinging.
PaulH.
http://freespace.virgin.net/paul.hunt1/
-----Original Message-----
From: Pearson, Tim <tpearson@westpac.com.au>
To: 'mgs@autox.team.net' <mgs@autox.team.net>
Date: 17 June 1999 03:10
Subject: Pinging, compression ratio, and advance....
>OK then gents (& ladies):
>There is always a certain amount of debate over what is the correct timing
>to use to prevent pinging and get best performance. Everyone seems to have
>their own ideas, which can usually be summed up as "advance till it pings
>under load, then back it off a bit"
>I've noticed a lot of people saying they use 15-20 deg BTDC.
>The factor which never seems to be mentioned is compression
ratios/pressure.
>Of course, the higher the comp ratio, the less advance you can get away
with
>for a given octane rating.
>
>The reason I raise this is :
>66B. 18GBUH engine. Compression pressure = 170. K&N filters, #6 needles.
>Mild cam. Stock distributor. Free flow, single muffler exhaust. NGK BP6ES
>plugs.
>Local fuel here is about 94 - 96 Octane leaded.
>
>Dynamic timed at 700rpm, vaccuum advance disconnected and blocked at carb =
>5-7 deg BTDC.
>And it still pings very slightly under heavy load (like full throttle, 3000
>rpm up a steep hill) when warm.
>
>Now, either I have something very strange with my engine, or I am doing
>something very wrong, or everyone else on this list is imagining things
(and
>I'm not quite egotistical enough to believe that!). I've tried
disconnecting
>the vaccuum advance; this helped the pinging problem, but introduced
>hesitation on sudden throttle opening (not entirely unexpected).
>
>Comments, anyone??
>
>Tim
>66B rdstr YGHN3-3238
>
>
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