Cam Profiles

Cam lift at cam intake exhaust duration

250, early 6 USA, GT6 I 0.230 10-50 50-10 240 (Part #307621)

TR5, TR6 PI to 73 0.250 35-65 65-35 280

GT6+, early Mk III 0.230 24-64 64-24 268

72 on USA, 73 on all 6 0.240 18-58 58-18 256 (Part #311399)

S2 Competition 0.270 31-71 71-31 282

S4 0.273 42-71 71-42 293

Kent "Fast Road" 0.260 288

Kent "Road/Rally" 0.273 280

Kent race & road 0.293 280

The two Kent cams are similar to the S2/S4 cams, but are available today.

The figures mean this:

lift at cam

The maximum height of the lobe over the heel or at rest position, or how far it will move the pushrod.

intake

First number is degrees Before TDC valve opens, second after bottom dead center when it is (well, should be) fully closed.

exhaust

as above, but before BDC and after TDC

duration

Degrees during which cam is lifting pushrod, which of course translates to how long the valve is open.

All the degrees are referenced from the crank, remember the cam turns at half the crank speed. The numbers themselves are not as important without some knowledge of the ramp, or actual graph of lift vs. time. The same ramp that works on a small block Chevy might not be the best for the Triumph 6. Crower grinds good Triumph cams from what I hear, but in the class I race we need to use stock profiles. Like the 35-65 PI cam, of course! Also the lift at the valve will be 1.5 times the lift at the cam, and 1.6 ratio roller rockers are available if you have $$$, on the order of $125/cylinder.