Cams......decisions decisions

[Super73]

Let's throw duration and LSA out the window and look at things that actually matter, valve events!!

228R cam 228/228 .588/.588 112 (assuming a 112 ICL)
IVO – 2* BTDC
IVC – 46* ABDC
EVO – 46* BBDC
EVC – 2* ATDC
Overlap – 4*

Tick cam 231/235 .630/.600 111+2 cam
IVO – 4.5* BTDC
IVC – 46.5* ABDC
EVO – 56.5 * BBDC
EVC – 1.5* BTDC
Overlap – 3*


Assuming these are using the same cam lobe (comp XER – 49* from .006 to .050) and the lift is the same; they are going to have almost exactly the same dynamic compression based on where the intake valve closes at .006.
70.5* ABDC for the TSP
71* ABDC for the Tick

IVC at .050” also has a major role where peak power is made. Being they are both within 0.5* of each other, I care to bet they will make peak power at the same RPM.

Overlap is near identical, so they are going to idle almost exactly the same.

With that said, I like the Tick cam better for 3 reasons.
1) IVO is 2.5* earlier – Opening the intake valve sooner means it will be at higher lift as the piston is moving down the bore. This translates to more air to fill the cyl.
2) EVO opening is earlier with the Tick cam allowing a reduction to pumping losses and giving the exhaust more time exit the cyl.
3) The overlap is biased towards BTDC vs ATDC. This should have an impact on reversion at lower engine speed and may result in a more stable idle


Now, I did not go in to lift, but I lean towards the Tick cam again.