I am going to run the Texas Giant on my new 402 but I can't decide on lobe seperation. I am caught between 112 and 114. The cam is built on a 112 but I want a little more DCR and idle vacuum. Which will give me more? According to the DCR calculator I am useing the 112 will. It just seems to me that the wider lobe seperation would keep the intake and exhaust valve closed longer threrefore increasing DCR.

So basicly, does a tighter LSA increase or decreas DCR?

 

The ICL determines your "DCR" so if both cams were installed at the same intake centerline than they would both have the same "DCR" but the wider 114 LSA cam will open the exhaust sooner the the 112 LSA cam will.

If both cams are installed at the same amount of advance or retard then the tighter cam will have more "DCR" since the intake valve will close sooner.

On your vacuum the amount of overlap is a major factor so the tighter cam with more overlap will have less vaccuum usually.

 

Thanks again Erik. I went with the 112+4 to get the DCR up. The other is a 114+4. I think that would change the ICL from 108 to 110 wouldn't it? I don't know how that effects things. As long as I have enough vacuum to run the brakes and the MAP I will be fine.

 

Yes you are correct!