I always used to use a vacuum gauge to adjust the timing in the 70s, and
recently rediscovered it and redid the B. You advance the ignition till the
needle just starts to flick (misfire) then back it off 3/4 of a degree.
Takes account of the actual conditions of your engine instead of the
summation of all possible worst cases that Bill mentions. Made a
significant difference to the performance and economy, and no pinking.
PaulH.
-----Original Message-----
From: William Eastman <william.eastman@medtronic.com>
To: mgs@autox.team.net <mgs@autox.team.net>; autox.team.net.mgs@B-LEADS1
<autox.team.net.mgs@B-LEADS1>
Date: 25 January 1999 04:50
Subject: Timing tricks
>I have always taken ignition timing from manufacturers with a grain of
>salt. These are chosen such that the worst case stackup of tolerances will
>not cause detonation. Each car is different and almost all cars can
>benefit from added advance.
>
>This is especially true for U.S. spec cars built after 1968 and before
>computer control. In these cars, settings were not chosen for performance
>but for emitions control. One of the worst offenders is the infamous
>vacuum retard that is attached to many post 74 LBC's. I am not sure
>exactly what ill this was supposed to fix but I believe that it is to keep
>combustion temps down for NOx and exhaust temps up for HC's. It also helps
>keep the idle slower with all of the air leaks introduced by the emissions
>crap.
>
>I was just getting into engine tuning in the early seventies so I have
>spent a lot of time trying to keep these Rube Goldberg devices working or,
>at the least, not destroying how the engine runs. One of the "on the
>street" hot tricks was to advance the cam timing one tooth. We did this
>on our '74 International pickup truck and it did seem to help. In any case
>I believe that most of the cars of this time frame do have the cam timing
>more retarded than typical. I believe that this is to keep the intake
>opening later so that there is less scavenging of raw fuel into the
>exhaust. Whether MG's fit with this is beyond me but maybe someone else
>knows.
>
>Even without emition issues, most cams are installed in a slightly retarded
>condition. This is because engine performance falls off more slowly with
>retarded cam timing than it does with it too far advanced. The number that
>stick in my mind is that small block Chevies have their stock cams
>installed 4 degrees retarded from the factory. Again, how MG's fit here I
>don't know but, given the history of the British auto industry, I doubt
>that they had better control of specifications than GM. They were probably
>using the same tooling to build these engines in the eighties that they
>used when the assembly line was set up in the- well I am guessing the
>fifties but it may have been much earlier. I read somewhere that Jaguar
>was still using the tooling Lyons bought from Standard right after the War
>to build the last XK engine in the eighties. This tooling was originally
>developed to build flat head Standard engines in the thirties.
>
>So what's the point of all this? Once again I have wondered off the
>original topic. Screw what the manual says. Advance your timing until it
>runs best and doesn't ping too much or kick back against the starter. If
>you can, buy a degree wheel and time your cam right to get the best
>performance. I did not do this when I assembled the A because I am lazy
>and was pressed for time- I needed the car for transportation while my
>other car was at the body shop. Other wise I would have probably bough a
>cheap degree wheel, a cheap dial indicator and magnetic base, and found out
>where I was. Someone sells offset bushings for the cam gear or offset keys
>for the crank gear to adjust the cam timing without one of those wonderful
>but very expensive adjustable cam gears. If you take the time to get
>everything right, your engine will run better. Usual disclaimers apply.
>If you can't hear the detonation or go lean and burn holes in your pistons
>Then I will deny any knowledge of this e-mail, this list, or MG's in
>general. This e-mail will self distruct in 10 seconds, 9,8...
>
>Regards,
>Bill Eastman
>61 MGA who has not seen a timing light since she followed me home and has
>no holes in her (still original) pistons.
>
>
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