>From: Parkinson,Ron
>For my $.02, I have a modified late TD, and use the shorter reach plug
>(colder) because of the higher compression. The theory as I remember
it
>is that the longer reach (hotter) plug can act as a glow wire like in a
>diesel and cause a pre-detonation or knock.
>
>Remember if you are using a sport coil you can run a wider gap than
spec
>as the addition volts will still arc and that will help.
I have not heard of using a short reach plug in a late head, wouldn't
it be better to use the correct reach plug with a suitable heat range?
What compression ratio are you using? I have a TD with a TF head
shaved for 9:1 compression and it runs fine on premium unleaded fuel.
I use NGK plugs.
..
>From: Douglas Ormrod [mailto:douglas.ormrod@neurological.org.nz]
..
>Hi T folk
>
>.... So my question is what plugs should I use - is it the
>head
>that determines choice - and can I find out without taking it off!
The head determines the reach plug to use. Late heads should have
an 8842 raised number with a 5 stamped after the raised number on
the top front right corner of the head. These use the long reach
plugs. Earlier heads have a completely raised number on the top
front right and use the short reach plugs. I can check an early
head at home tonight for the number if that's helpful. You can also
pull a plug out and measure how deep the threads are.
Bill Putnam
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