[TR] TR4A - Tuning Update

[Geo Hahn]

In my experience, a broken tensioner will give you a lot of noise, easily
traced to inside the timing chain cover.  An excessively worn chain (with a
good tensioner), not so much so.

Geo


On Wed, Nov 20, 2013 at 10:25 PM, G.D. Huggins <guy at genfiniti.com> wrote:

> All,
>
> First, thanks for all of the suggestions to date!
>
> In my obsessive desire to get the car to "purr" at idle, I have:
>
> Set the valve lash (I even measured the cam lobes for good measure)
> Set the timing
> Set the idle
> Set the mixture
>
> I am getting between 20-21 vacuum at the intake manifold.
> Roughly 185 compression on all four cylinders
>
> But I was still getting a "jumpy" idle, normally varying between 800-900
> RPM,
> occasionally dropping into the 700s..
>
> So, on a suggestion from Randall I went and got myself a timing light and
> found the timing is jumping, to the advance side.
> Hmm.. maybe the dizzy gear end float.
> Checked it.  Just over .007.. just exceeding the upper limit.
>
> But I thought, maybe its the Pertronix dizzy with a loose advance.
> Pulled it out and dropped in my recently rebuilt Lucus tonight.
> Set it to the same timing as the other (8' BTDC), and I still have the
> jumpy
> timing, again to the advance.
>
> So, I've got something that is causing the spark to fire too soon at idle.
> But it evens out when I give it some throttle.
>
> At this point I am suspecting that maybe that dizzy gear is jumping around,
> causing the sporadic advance.
> But this space is taken up under throttle.
> Or, the timing gear/chain has got some sort of slop.
>
> I'm considering having my dizzy pedestal shaved done .003" to take up the
> float space, and/or replacing the dizzy gear.
> I'd like to eliminate these before diving into the gear/chain.
>
> Anyone know where I can source a "new" dizzy gear?
> Anything else I am not thinking of?
>
>
>
> Cheers,
>
> Guy D. Huggins
> 1965 Triumph TR4A
> CTC 63569LO
>
> Online project diary at http://www.genfiniti.com/triumph
>
> ** triumphs at autox.team.net **
>
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