Looking for more pep off the line
Both Richard Holdner and Steve Dulcich praise this particular camshaft, and I trust their opinions. Now I'm undecided as to my LSA, if I should just go with the 110 or if I should have one ground at 107. My build is just supposed to be a hot rod/street machine, not a full racecar.
Definately a good street cam. Comp Cams description and specs:
XE268H - 10
For 273 to 360 LA engines. That is a fairly wide CID spread. In a 273 it should be fairly lumpy while in a 360 it should be fairly smooth. That sentence is my comment.
At 0.050 tappet lift; I 224°, E 230°.
Adv'd ; I 268, E 280°
LSA ; 110°
Valve lift ; I 0.477, E 0.480
Largest recommended for a stock converter. In 273-318 it is best with a 2,000 stall.
This is Comp Cams information.
Again I recommend looking up and watching David Vizard's Powertec 10 videos on camshaft selection. One directly discusses the 128 formula.
Another good source of information is High-Performance Cams and Valvetrains by Billy Godbold, ex head cam designer for Comp Cams.
Both gentlemen are highly knowledgable in engines and camshafts. Billy comes at the selection process from an engineering perspective of getting relevant information regarding the engine and intended use. From there he picks the EVO then the IVC and finally the IVO and EVC points. David comes at it from the other direction and simplifies the decision making process for those of us less technically "in the know".
I do not dispute that the XE268H is a good cam. At Summit you can find it listed as XE268H-12 also. This is protecting them from the more is better think. A 112° LSA may allow an engine to pass an emissions test that a tighter LSA would fail.
After watching DV's videos more than once on cam selection and reading Billy Godbold's book, along with DV's book, How to Build Power, I feel considering a new cam will be purchased and ordering it with the LSA you want, costs no more, I recommend 106° LSA or 107° LSA as a sesecond choice. 105° would be good if a lopey idle is acceptable. This would work well with 10.5:1 CR and probably 11:1 CR. With distilled water injection with 2% water soluble oil as used in machine shops, there would be no problem burning 87 fuel. Chose a large enough water jet to control detonation by using a pressure switch to turn the pump on. At high vacuum.which is low manifold pressure, detonation is not an issue. As the throttle opens manifold pressure increases along with the tendency for detonation. Water cools and slows the combustion process, so a couple more degrees of advance can be dialed in. Water adds no emission components and reduces NOX.
Watch DV's octane video for a more in depth explanation