THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

No that is a good question. The vernier comes with a distance piece set at 1 inch so you can regularly check it is correct. I also checked the 0.025 feeler gauge which happily is actually 0.025 according to the vernier.

Good point though when checking measuring tools.

I have seen some pictures where two tape measures have been set side by side and the lines for inches and mm don't even line up correctly across the two tapes.
Problem is which one is correct the feeler gauges or the vernier gauge?
Only asking for a friend.

Whilst I’m sure many readers will have experience of poor quality parts I’ve just resolved a problem with setting my plugs and for the most unexpected of reasons. The car is modified and runs a 123 tune+ distributor (very good) and I have found a plug gap of 30 thou works well.

Having replaced and set new plugs I wasn’t getting the running I was used to. The problem…….have a look at the pictures above!

Yep, the feeler gauge is marked 0.030 but is actually 0.025. This was quite an expensive gauge set bought some years ago but I have to say, it never occurred to me to check they were correct.

Plugs are now set to 0.029, which is correct according to the vernier dial gauge, and the engine is back on form.

Satisfying to have worked it out but what are the odds?

Ian.