Neil:
Your carburetor settings did not cause the problem! End of
story.
Any mechanical problems were there to begin with. Getting the
engine running with full potential output may have broken loose
something that was already failing. But it takes time for incorrect
settings to damage a mildly stressed street engine.
This may not be applicable, but it seems like a good place to
mention it.
Two other unusual reasons for engine knocking I have seen. 1. Ingested
nuts, bolts or washers (been there, done that) sounds like a rod knock.
2. Intake valve adjustment way too tight. Allows exhaust gas into the
intake manifold, the carb. dash pots bobble up and down clonking on the
carb body.
Take heart. Fix only what you see as necessary to get you by.
These engines are very forgiving and will run for a long (albeit
rackety) time with mismatched parts in them. A fully balanced engine
with matched new components is a joy to drive. But an engine with
mismatched pistons and used tappets will fire up and run every day too.
Kelvin.
-----Original Message-----
From: Neil Cotty [mailto:neilc@tradesrv.com.au]
Sent: Tuesday, December 01, 1998 5:14 PM
To: mgs@autox.team.net
Subject: Re: and you thought Titanic was a Disaster..
Hi all,
Well I guess I'll be poking around tonight removing the sump first as
it's
the easiest, trying to look down the spark plug holes (sorry no
boroscope -
oh btw I can spell 'Titanic' <G>) etc. The spark plugs were all nice and
brown on the tip but a couple of them had some oil around the base, tiny
bit. Absolutely no sign of damage on the plugs. Someone mentioned a bit
of
carbon could have dislodged from the top of the piston and thats what
I'm
hearing, I'm afraid I'm not game to try breaking it up with the rev
test!
Knowing my luck as it's running at the moment, I'll punch a hole in the
block!!
I really, really hope it wasn't my carb settings that caused this -
Barney
my timing was on spec (at least over the last 6 months) - 20 degrees
BTDC at
1000rpm, vacumn removed. I think one of the reasons why my timing was
weird
yesterday was because the car was not fully warmed up and idling well
(?).
It was running at it's normal temp - mine always sits 3/4s between Cold
and
Normal and only gets to normal when it's idling on a really really hot
day
or I'm giving it heaps. It doesn't overheat - new water pump, hoses,
radiator recore etc, doesn't lose a drop of water.
I feel sure it wasn't overly lean, mainly because it seemed to me, and I
have NO experience at this but when it was lean while I was tuning it,
the
exhaust had a *really* distinctive splashing sound to it, when
enrichening
the mixture the splashing went away to a steady beat - sounded great,
the
note altered again to offbeat - no splashing with a black exhaust when I
went too rich - just like the manual says it should. Maybe the thing
wasn't
used to getting so much good mixture into it as it used to have the
biased,
lean needles, leaky carbs, leaky air pump botched manifold etc and this
extra power was too much for the rings/piston or whatever's broke. Am I
dreaming? <G> I don't know. You tell me, but I felt a distinct 'whoaa
baby'
push in the back after my final alterations and a *sob* minute or so
later
'Titanic' impression by the engine! <G>
Let y'all know what I find. Thank you very much everyone for your help,
valuable experience, and kind words. Feel better to know I'm not the
only
one who's been through this! I guess you have to make some mistakes to
learn
from them.
One last question - is it ok for me to just fix the one piston with the
problem? I was wanting to drive the car till end January when I was
going to
rebuild the motor completely for racing. Can I get away with just fixing
one
piston, new head gasket, rings etc?
Cheers,
Neil.
--
Neil Cotty - Sydney, Australia
1970 MG B GT / 1959 MG A 1600 Mk1
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