Triumph Repair: TR4 and Stromberg tops., piston movement, dash pot

Question
Why did they lengthen the dashpot height on the Stromberg 175CD carb,after the TR4 ?
Reason for asking is important too.,-  Looking at 'GOODPARTS' site for triple Stromberg 175, set up for use on a 2.5 TR6 CP( will be cc equiv')engine inside a GT6, They recommend using the 'shorter dashpots off the TR4,or else the bonnet wont close properley.

Answer
The top of the dash pot must match the carburetor so as not to restrict the travel of the piston. The lump in the hood of a TR-4 was so that there was clearance. I have never tried to mix up dash pots on Stromberg carbs so I can't tell you which will work with the wrong carburetors. It seems to me that if a shorter top were used then that would restrict the piston movement which will not work. However, if the shorter top and piston were used and the piston travels so as to open all the way, it may work. Not sure. Let us know if it works.
Howard