have you checked the valve clearances ie tappets? if they are out it does
affect compresion.
spark - can you measure volts actually on the points? incorrectly assembled
you can short out the supply, quick test: ign. on open close points with
screw driver should get spark. if this is ok stuff the lead into the coil
and hold near ground point spark here indicates fault with cap/rotor
leads(cant be all leads !)
good luck!
Derek Watson
74 B V8 roadster
83 Austin Mini Van
Scotland
----- Original Message -----
From: Neil Cotty <neilc@tradesrv.com.au>
To: MG List <mgs@autox.team.net>
Sent: Tuesday, March 30, 1999 3:56 PM
Subject: Bad Compression & No Spark
>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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