Whilst the distributor drive gear *can* be installed incorrectly the
distributor has to be twisted from its correct position to compensate in
order for the engine to run. If the engine is running then No.1 cylinder
*must* be getting its spark at about the correct time i.e. TDC for that
cylinder and No.3 must be getting its spark half a crankshaft revolution
after that. Therefore if the timing light shows the TDC marks lining up (or
near enough) on No.3 cylinder and not No.1, then the marks are out not the
distributor. Either the pulley is incorrect or bad, or the timing cover
marks are incorrect, or a combination of two or three. My car has the
pointers by the alt, and the earlier cars had them below the pulley, but as
far as I can see from pictures the two sets of marks are *not* 180 degrees
apart. I'm trying to imagine here but it seems to me that if you *should*
have a cover with the marks on the bottom, and the timing *is* occuring
BTDC, then 180 degrees out from that could well be *after* TDC as measured
on the top marks i.e. you have the wrong cover.
The first thing to do is locate TDC. You can do this with a measuring rod
in No.1 cylinder plug hole. Turn the crank until the piston is near the top
of its stroke - say on the up stroke. Make a mark on the rod at a datum
point on the block and a mark on the pulley. Now rotate the crank so that
the piston is at the same position on its down stroke as measured with the
rod using the datum point you marked before, and make another mark on the
pulley. Between those two points is TDC. Now you can check your timing.
Then you can worry about why your marks are out.
PaulH.
----- Original Message -----
From: Max Heim <mvheim@studiolimage.com>
To: MG List <mgs@autox.team.net>
Sent: Tuesday, October 17, 2000 11:47 PM
Subject: Re: where is the timing mark?!
> Well, you can check one thing very simply. First note which position on
> the cap the wire from the #1 cylinder (furthest forward) leads to (it
> could be any of them, depending on the position of the distributor body).
> Then remove the distributor cap without removing any of the wires (you
> can detach the center wire to the coil if it makes it easier). Now note
> where the rotor is pointing. Turn the engine over (by rolling the car in
> gear, or turning the crankshaft pulley nut with a wrench) until the rotor
> is pointing at the position of the #1 spark plug lead (you can test fit
> the cap from time to time to get this correct). At this point the timing
> mark on the pulley should be in sight, somewhere in the general vicinity
> of the TDC mark (if the car was running at all). If it is not (as appears
> to be the case), then you have a problem!
>
> One possibility is the fact that different years had the timing marks
> attached in different positions on the timing cover, and therefore
> required different pulleys. If some DPO installed either a timing cover
> or a pulley from the wrong year, it would result in the problem you are
> experiencing. I agree with the comment that the odds of pulley "slip" are
> very remote.
>
> The distributor itself is keyed and cannot be installed 180 degrees out,
> but the distributor drive gear could be, although that seems very
> unlikely. The position of the vacuum advance pot unfortunately doesn't
> tell you anything, since one can rotate the entire distributor in
> increments of 90 degrees, and compensate by shifting the spark plug leads
> one position in the opposite direction, in order to end up with the pot
> aiming in whatever direction seems to be convenient.
>
> I hope this helps.
>
>
> Evangelos Makris had this to say:
>
> >Thanks people for your helpful ideas.
> >When the strobe pin is on cylinder #3 the mark appears to be 10-15
> >degrees AFTER
> >TDC, that is, further clockwise from the 0-degree notch.
> >
> >So, how do I start checking if something is indeed 180 degrees out and
> >correcting it?
> >
> >Is there a picture somewhere on the web that shows *approximately* where
> >the
> >vacuum advance unit points when it's timed OK and to which of the four
> >holes on
> >the distributor cap the #1 sparkplug lead goes?
> >
> >What is a gulp valve and where should I look for it? I have two HIF4
> >carbs and a
> >small almost cube-shaped Facet electric petrol pump. When the engine is
> >off but
> >the ignition is on, that pump won't stop ticking after a while, like the
> >
> >standard SU electric pump does on my 66 Sprite after the carbs fill up.
> >
> >Evangelos, 73 BGT
> >
> >
> >
>
>
> --
>
> Max Heim
> '66 MGB GHN3L76149
> If you're near Mountain View, CA,
> it's the red one with the silver bootlid.
>
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