Jorlain

iTrader: (4)

Hey Guys.

I'm a little confused as to what specs I need for the cam for my build. It seems like everyone uses the terminology differently and I'd really prefer to order the right thing the first time.

Essentially I'm mimicking a David Vizard build. The build is listed in "How to Build Max-Performance Chevy Small-Blocks on a Budget" on page 150. It's also similar (or maybe even the same) as the Budget Sledgehammer build located here: Link

From the book: "... custom single-pattern COMP Magnum hydraulic roller grind number 3119. This cam, ground on a 108 lobe centerline angle (very important to stick that LCA), with an advertised duration of 280 degrees, had 224-degrees duration at 0.050 lift delivered; with 1.6 COMP Magnum rockers, 0.560 lift."

He also summarizes it as "COMP Cams 280 Magnum on a 108 LCA in at 4 advance."

Now, Vizard uses the term LCA, and this is what's confusing me. In the Sledgehammer build they call for a 108 LSA with 4 degrees of advance (ground in, I would assume?).

Going through all the information that I have available to me, I got a quote from Comp Cams for the cam.

Here is what it would be:
Lobes: 3119S\3119S
Actual Duration: 224/224 @ .050
Lift: .560\.560 (1.6 Rocker)
LSA: 108
Advance: +4 (This would make the ICL 104, right?)

Installed it would be dot to dot, right? Does this look right, or am I off on something?

Thanks!
-Mike

skinny z

LSA: Lobe Separation Angle
LCA: Lobe Centreline Angle
Yes, one in the same.
+4 would move the ICL to an advanced position (104 ICL on a 108 LCA) and you should be able to install the cam "dot to dot" . That said, it's never a bad idea to degree the cam to verify everything is going together properly.
Keep in mind that Vizard's cam specs have changed a great deal in the years since he wrote that first book. I have both editions and there is quite a difference between the two. There are better cam profiles out there and Vizard spec's those if you want to stick to one of his builds.

Jorlain

iTrader: (4)

The book I'm pulling this from is the second version written in 2009.

Thank you for clearing the confusion of LSA vs LCA. After reading what seems like hundreds of posts, I couldn't find a clear answer. There were many that argued that the LSA and the LCA were and could be different, but I couldn't figure out how or why. At this point I thought they were mistaking LCA for ICA, and now I feel that must have been the case.

Hopefully this will help someone else down the line that runs into the same issue, too.

Thanks!

Valve Motion

There is only one camshaft requirement equation and it was originally written by Ed Winfield in 1948, but you can find it in Controlled Induction Software. It isn't a toy, or a joke. This software has been used for the past 25 years and is accurate. You need to check it out on my website. See my signature. It has a money back guaranty. This is the real deal.


And that's not true, Lobe Separation Angle is the degrees from Exh lobe centerline to Int lobe centerline in cam degrees. Lobe Centerline Angle is the degrees from TDC the profile centerlines are located, measured in crank degrees.

Orr89RocZ

iTrader: (20)

Welcome Mr. Jones!

skinny z

For the purposes of the discussion at hand, (as asked by the OP) using LCA to describe the distance between the lobes would be one and the same as LSA. That is to say, the distance between the centrelines of the exhaust and intake lobes is the lobe separation angle. That's all that's meant in the preceding statement.
Further to that, referring to a any individual lobe would then be described as the Lobe Centreline Angle. In the text the OP was referring to, and one I'm sure you are familiar with, the two terms are interchanged but only in the context of the article written.
I hope that clears that up.

Valve Motion

Mike, you are right. David is calling the 108 lobe separation angle, the lobe centerline angle. I've been designing and grinding camshafts for over 30 years. You have the Lobe Separation Angle, and then you have an intake lobe centerline and an exhaust lobe centerline. You can add "angle" if you want.