parkplug well too long for high cylinder ?

[Nick Lettington]

Thanks RR... re checkin the valve clearance, that's what I was saying above, though the comment is hidden under the last photo... but i still wonder if Speedex and Ricardo heads have the plug slightly shielded in the threads, is there a benefit?

[Colin Reed]

HI NICK,
You could put a taper down to where the plug ends.
I would doubt there is any benefit having a recessed plug I think the opposite would be true.

Colin
NZ

[Michael D]

Do you think that it necessary to machine the sparkplug well to reduce by the top the head cylinder

@ Creusois: this indeed looks like a Ricardo head. From correspondence with David Dye (who sells new Ricardo heads) I've learned that there is very little room to modify the head (f.i. by machining) due to the proximity of water passages. When you take a look at the Ricardo patent drawings in Nick Lettingtons' post (#6) it's obviously clear that machining the spark plug hole is tricky to say the least; you might break into the water passages or in the best case scenario have very little alloy left between the spark plug hole and the water passages..  So I'd rather fit a spark plug that's  flush like Reckless Rat has indicated (in post # 10 referring to post #6). Skimming a repro Ricardo head is tricky too. But if in doubt: consult David Dye. PS: the head you have does not resemble the Ricardo head I have as manufactured by David Dye