What kind of impact will a 2^ increase in LSA have on my turbo motor? I currently run a Bcam with 1.7 rockers. I keep reading to swap to an F cam. To ensure p-to-v clearance, I would need to run the Fcam with 1.6 rockers, to maintain my .512 lift. However, the duration is a +2 with the f over the b, and the LSA is +2 with the F over the B

 

Overlap = ((intake duration + exhaust duration)/2 - (2*LSA))

Therefore, LSA means nothing without the lobes it's run with.

The B303 has 2 degrees more overlap than the F303.
The F303 has 2 degrees more intake and exhaust duration than the B303.

The F P2V clearance should be MORE than with the B.

When the valve is at peak lift, the piston is NOT at TDC. It's all about ramp-rate and overlap as to how much P2V clearance you will have. In this case, an F with 1.6's is less aggressive than a B with 1.7's. Couple that with 2 degrees less overlap with the F & it should clear the pistons easier.

As far as power goes..... The F is probably worth 5-10hp over the B at peak HP and 5-10 less at Peak TQ. Of course, this really depends on the rest of your setup, along with how the B is currently installed and how you plan to install the F.

 

Thanks for the reply. I have been reading a ton on cams today. My B was installed straight (non-degreed) to me, meaning dot to dot. As I have read, the dot to dot may not be straight up. Most install the f straight up, and I will prolly do the same, instead degreeing it this time.

 

b overlap would = (224+224)/2 - 2*112 = 0

f overlap would = (226+226)/2 - 2*114 = -2

So the B has no overlap? and how would negative overlap work with the F?

 

You're calculating overlap at .050" lift. The F does have overlap, just not at .050" lift. (try comparing the 2 at .004 or .006 lift)

'Stright up' means the LSA = ICL
Dot to dot on both of these cams is 4 degrees advanced.
Most install the F 'stright up', which means retarding it 4 degrees from 'as ground'.

 

makes perfect sense. So my b cam is +/- 4 advanced. That would effect performance. I will degree the F when I install it.

Thanks for helping me out.

 

Technically "straight up" is installing a cam with split timing.... or LSA=ICL
Dot to Dot is installing with whatever advance was gorund into the cam.

But in the real world, most guys when they say installed their cam straight up USUALLY mean they put it in dot to dot...ie, no advance or retard on the chain/gears.... which is 4 degrees advanced in most cases with comp cams, 5 degrees with the F303. Enigne builders know better, but even they confuse the issue with the advice they give lol.