I've seen all the posts regarding the proper plugs, timing, etc. for TR's,
speciffically 6's. What I wonder now is, do the original specs for the TR's
plug type, gap, timing etc. change with the introduction of no-lead gas?
Thanks in advance,
Jeff Wages,
'71 TR6
> -----Original Message-----
> From: Power British Perfrormance Parts, Inc.
> [SMTP:britcars@powerbritish.com]
> Sent: Thursday, October 29, 1998 2:43 PM
> To: triumphs@autox.team.net
> Subject: Re: TR-2,3,4A - Retard timimg for use with 92 octane gas?
>
>
> John,
>
> You should use the lowest octane fuel you can provided the engine shows no
> signs of
> detonation. Octane actually makes the fuel harder to ignite, hence it's
> use in very high
> performance engines. These engines make their power from the compression,
> not the octane
> in the fuel. An engine's power output is a funtion of the pressure
> created in the
> combustion chamber above the piston. The more compression, the higher the
> pressure at the
> moment of ignition and the more "push" down on the piston.
>
> As the air/fuel mixture is compressed, the temperature goes up. The more
> compression, the
> higher the temp. At some point, the fuel may spontaneously ignite prior
> to the spark plug
> firing. This is detonation and it is very bad for an engine because it
> often occurs just
> before the plug fires. You then end up with two flame fronts in the
> cylinder that crash
> into each other which can crack pistons and rings, etc. Most often in TR
> engines, I find
> cracked ring lands (the area between the topmost two rings) to be the most
> likely victim
> of detonation damage.
>
> Octane is added to the fuel to reduce the chances of detonation. In doing
> so it actually
> slows the combustion process. The lower the octane, the faster the flame
> front spreads
> thoughout the combustion chamber - this yeilds higher cylinder pressure
> just after the
> piston passes TDC, and theoretically more power for any given compression
> ratio provided
> there is no detonation. Bottom line - for best performance, run the
> lowest octane you can
> that does not cause detonation.
>
> As far as timing goes, you must do some experimentation to find the best
> combination for
> your engine. Most motors will make good, reliable power with a full
> advance of 28 - 34
> degrees total timing. Double your distributor advance, then subtract from
> your desired
> total timing to find your initial timing. (e.g. If your distributor
> weights are stamed
> with a 12, then that is 12 degrees distributor advance. 12 degrees x 2 =
> 24 28 - 24 = 4
> degrees before top dead center initial timing.) You must make timed runs
> and compare
> results to find what is the best for you. The amount of advance the
> engine will tolerate
> depends on the quality of fuel you're using, the general condition of the
> engine, and the
> atmospheric conditions in which you live. First, make sure your carbs are
> tuned properly
> and that your car is fully warmed up by driving for a few miles. Then
> find a flat length
> of secluded roadway to make some tests. Start on the low end of the
> scale, set your
> timing, and make a timed acceleration run in top gear between 30 - 60 mph
> (helps to have
> an assistant in the car with you to record times with a stopwatch).
> Advance the timing a
> few degrees (try 2 degrees to start) and retest. If at any point, you
> hear detonation,
> stop the run and retard the timing until the detonation goes away. You
> will find your
> runs get faster to a point and then fall off again. If you continue
> advancing, detonation
> will set in. Once you find your fastest timed run, set the timing to that
> figure provided
> it is at least 4 degrees away from the point at which you heard
> detonation.
>
> I bet if you spend an afternoon experimenting, you'll be surprised at how
> much better your
> car will run afterward!
>
> BTW if you find that the car idles too high after setting to your best
> performance, you'll
> need advance weights with more timing built in to bring the idle back down
> again.
>
> Regards,
>
> Brian Schlorff
> Power British
> http://www.powerbritish.com/~britcars
>
>
>
> John Cowan wrote:
>
> > Spec for timing of Triumph four bangers is 4 degrees before true dead
> > center. But this was written with 96 octane gas in mind and required.
> Is
> > anyone retarding spark to two or zero degrees as a matter of course in
> > order to deal with the the 92 octane gas that is the best grade
> available?
> > This was recommended to me.
> > Thanks.
> > John Cowan
> >
> > BTW, I toy with the idea of using a mixture of 92 octane and 100 octane
> > Aviation gasoline.
> >
> > Visit - In Their Own Words Website - an on-line non-commercial
> publishing
> > experiment, plus movie reviews, articles and Left/Progressive links at:
> > http://home.earthlink.net/~jfcowan
>
>
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