I would check the TDC mark on the pulley is correct, it consists of a
steel-rubber-steel sandwich and can delaminate, and the outer turns relative
to the inner.
PaulH.
----- Original Message -----
From: Jones, Mark <MJones@ngl.ca>
To: <mgs@autox.team.net>
Sent: Monday, May 08, 2000 2:21 PM
Subject: Timing question
> Sunday I decided that I should check the timing on my 73 MGB GT. I found
> the timing to be at 10 degrees AFTER TDC. So I checked the manual and it
> says for a 18V engine with a 25D distributor, the timing should be at 13
> degrees BTDC. I adjust the dizzy to 13 and of course the car now barely
> runs because the carbs were setup to work at 10 degrees ATDC and are way
out
> of whack. I mean the idle screws were completely backed off and the jets
> were all the way down. So I adjust the jets and idle by the book and had
> the car idling around 800 rpm. The car is running smoother than ever
> before. Take it for a spin and it is pinging under any type of load. Ah,
> unleaded gas and lower octane fuel! So I backed the timing off to about 7
> degrees BTDC. Take it for another spin and the pinging is gone but is
> replaced by a bit of backfiring when I lift my foot off the gas pedal. I
> checked my plugs and they are a nice brown colour so my mixture is about
> right. It is also not idling very well, but I am guessing that it is just
> an adjustment of the idle screws due to adjusting the timing again.
>
> The question is what should the timing be for my car given that we don't
> have leaded gas? Also, any suggestions as to what is causing the car to
> backfire?
>
> Mark Jones
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