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Bad Compression & No Spark

To: "MG List" <mgs@autox.team.net>
Subject: Bad Compression & No Spark
From: "Neil Cotty" <neilc@tradesrv.com.au>
Date: Wed, 31 Mar 1999 00:56:06 +1000
Hi all,

Well I've been slaving over the A the last few days in a last ditch effort
to get it re-registered before it expires (T minus 3 days) and I have to go
through a 'Blue Slip' inspection which is a real ba***** of a thing in NSW.

The car overheated and blew a head gasket, thanks to a crack in the rear
welch plug (won't mention how I've 'fixed' that <G>). The compression
numbers were, err, bad before the overheating. 1-4, 120, 120, 150, 150.
Indicating some type of problem on 1 & 2. Well, with the head off I decided
to lap the valves (also removed all the carbon from the chambers, ports,
valves etc), got the nice grey around the seats and the valves etc before
refitting with new seals etc. Now, with the car dry, I am getting 90, 110,
135, 135 - head torqued to correct settings (50lb). I put a little oil in #1
and #2 and the both went up by 10 only. Whats the deal? The seats looked
pretty sad on the exhaust valves I must say, and the guides had some wear.
At this stage I am only concerned with getting the thing to start and stay
reliable for the Pink Slip (easy) inspection. Can someone fill me in on what
I should be looking at here? Is it likely that I have stuffed valves and
rings on #1? and some valve issue on #2? My dubious logic tells me that
compression loss, due to valves is only due to Valve Seat and Face wear yes?
A sealing issue.

When I get a chance, later in the year, I'll rebuild this motor properly,
get the head fitted with new guides and seats, valves etc. For now it's a
fudge unfortunately. It only has to run for an hour.

Now to the no spark issue. Water was everywhere in the compartment. I've
rebuilt the dizzy with new points, condensor etc, set the gap. Now with the
line from the coil connected (not the line to the cap, cap is off) to the
dizzy, ignition on, I should be seeing a spark when the motor turns over
yes? Well no spark. Ideas? Is the coil dead? Connections 'appear' ok.

Thanks everyone,
Neil.
--
Neil Cotty - Sydney, Australia
1970 MG B GT        / 1961 MG A 1600 Mk1 / 1956 AH 100 BN2
GHD5UA200702G /  YGHN2 100102-1399 / BN2L-232789


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