49 Inter

Hi.

These figures come from the 'Building and Tuning the long stroke Norton Engine' notes compiled by Mitchell Barnes.

Inlet - 25thou min.

Exhaust - 40thou min.

P.E. Irving in 'Tuning for Speed' recommends 0.0625" or 1/16" in OHC engines, but then, rather confusingly, later goes on to say that "These will be the minimum depths, but thermal expansion of the piston, any rocking of this component in the barrel and taking up of bearing clearances, all tend to reduce the measured clearances, and the actual pockets should be cut 30 to 40 thou deeper".

It might be worthwhile having a word on Stu Rogers 01945 585116.

Regards.

Ian.

Or Barry Stickland