Hi all,
As a professed mechanical bunny, but gradually getting better :) - and
mainly from reading the clear explanations on various issues from other list
members.. :) I read a post from Barney a while back concerning adding a
40kv coil, gapping the plugs and setting the ignition to 20 degrees BTDC.
Barney also mentioned to back off the ignition if you were experiencing
pinging problems.
Well my 1970 BGT is supposed to be run at 20 degrees btdc at 1000rpm (and it
was). Barney suggested using a 97 octane gas and back off the ignition a
little if still experiencing pinging. That got me thinking - a rare event.
<G> Well we can't get that sort of leaded gas here in Australia. Nowhere
near it. Our Premium Unleaded is 96 I think and our Super (leaded) is umm
I'm not sure but I don't think I'd be pushing it to say high Eighties or
very early nineties. (some other Aussie?) I've tried octane boost etc but
that doesn't seem to help.
Anyway I tried backing my ignition off to 14 degrees btdc. I still have some
pinging but it's significantly reduced - but 'oh my gosh' I no longer appear
to have 'flat spots' in the rev range, it's powering through the trouble
spot (1800-2900rpm) and singing above 4000. I also replaced the coil as mine
was the original one (with a Bosh GT40T (no resistor) - half the weight and
size of the orig but ooo ugly!!! <G>) and gapped the plugs accordingly. But
frankly I don't think the coil change has made much of a noticeable
difference. *Maybe* it starts a bit better than before. The ignition timing
certainly has made the biggest difference because I tested this prior to
installing the new coil. I guess these 1970 motors were designed for a much
higher octane (?). It's funny because I notice the next year they changed
back to, what, 14-15 degrees btdc? Why? Any comments?
One other thing I've noticed. The compression in my cylinders ranges from
146-148 from 1-3 and it's about 140 on #4. The HT lead on number 4 and the
plug cover & plug appear to be extremely hot (at idle & after driving)
compared to the other three cylinders. Can someone explain why this might
be? Have I got a problem with the HT lead or is it/could it be something to
do with the lower compression in that cylinder? A valve problem? It's been
there before I messed with the ignition timing & coil. <G>
Have a good weekend all.
Cheers,
Neil.
--
Neil Cotty - Sydney, Australia
1970 MG B GT / 1959 MG A 1600 Mk1
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