Inlet Trumpet Lengths Twin Weber 40s

[TANGO7]

Anyone know what the recommended length is for the above, for a Crossflow 1600 Sprint for general road use?

[auyt]

Longer the better for torque. The Airfilter is more of a governor of the length. as there needs to be 1" clearance from the end plate, say on a K&N.

[TANGO7]

Yes, should have said the carbs are fitted with K&Ns which are 80mm depth. i was aware there was a balance between theoretically better torque at lower revs and "increased" performance at higher revs, depending on the length. I was after a balance between the 2 parameters so maybe go for something like 30mm length as the mid point, giving the required end plate clearance.

[TANGO7]

Just looked at Weale on this and he lists recommended Trumpet Lengths at 38mm for 1700SS and 1600BDR, 60mm for 1700BDR, but strangely actually states "None" for 1600 Sprint. Anyone any ideas on the latter for the 1600 Sprint (My type) and can anyone, running a 1600 sprint, confirm the lenghth of trumpet  they are using, if at all.

[Andrew Gilbert]

Mine were 50mm and gave a good spread over the whole rev range, but I made sure I had that 25/30mm clearance to the throat.

[Roy Blyth]

My 1980 1600 Sprint does not have any trumpets, just pancake filters.