[TR] Dieseling and pinging

[Randall]

> The head was shaved to raise the compression

Perhaps someone else knows if this applies to a TR6; but I know that on a
TR3 motor it is important to round the sharp edges created after shaving the
head.  Otherwise, the edges cause pinging and dieseling.

> My question is do I have to run high octane fuel or fuel additives or can
> I adjust the ZS carbs?

To take advantage of the higher compression, you need the higher octane
fuel.  You _might_ be able to get by on regular without pinging, by
retarding the ignition timing.  However, this will reduce both performance
and mileage; to likely worse than it was with a stock engine.

> What causes this? Will carb air/fuel adjustment fix it?

It may get better over time, if you get the mixture and timing right.  It's
caused by something in the cylinder (other than the spark) being hot enough
to ignite the fuel; which can sometimes be carbon from rich mixture or
misfiring.  But given your story, I doubt it will get better by itself.
You'd best learn to kill the engine with the clutch, just after you turn the
key off.

> with engine @ idle 800 RPM, and the vacuum advance
> still attached,

A US-spec 73 would not have had vacuum advance originally; has someone tried
to add it?

> I was no where near 4 ATDC.

So where was it?

> Should I be concerned that my
> vacuum advance is not working?

The stock setup on a 73 was vacuum retard only.  The VR was purely for
emissions control and not very good at that.  So my suggestion would be to
leave it not working, and ignore the 4 ATDC timing figure.

If it has been modified for vacuum advance, then the advance would not be
working at idle anyway.  VA is primarily for improved fuel economy (although
it does increase NOx emissions somewhat) so if you have it, I would suggest
getting it working.

But the bottom line is that you need to figure out what you have, in order
to know how to adjust it.

Randall