Are you going to be using a power adder?

those specs are real close to what i have know,that being said i dont think you'll make 800hp with that cam and the heads will have to flow really good.
on a better note, the lift is pretty spring friendly  so that wont be a real big issue but will still need to be checked on a regular basis.

just my .02

If I only knew what that was... 

Turbo, blower, nitrous?

I'm going to buy one of three cams, not sure which because i don't know what I'm looking at.    Originally I was going to have a cam designer/builder custom grind me a cam, but thats no longer an option ($$$). They're all really close to being the same... but a little different. Headers are dry SS. Looking for max HP, the lower in the RPM range the better.

int/ex

261/271 @.050
680/680
108 lobe sep.
110 centerline

260/270 @.050
680/680
110 lobe sep.
110 centerline

264/279
690/680
114 lobe sep.
110 centerline

Like I said, they're really close to being the same. Just wondering what numbers move the peak HP/torque lower in the RPM's.

The main differences in these cams is the lobe seperation.  Lobe seperation dictates how much overlap is involved. 
The 108 seperation will give the most overlap and roughest idle, along with the narrowest power band. 
The 110 seperation will give a better idle and a wider power band. 
The 114 seperation will give the smoothest idle.

Is this a roller cam?  Hydraulic or mechanical?

From what I can find a lot of blower cams run 114-115 lobe seperation (I don't know much about blower grinds).

If I had to choose I would go with the 110 seperation.

I'm going to buy one of three cams, not sure which because i don't know what I'm looking at.    Originally I was going to have a cam designer/builder custom grind me a cam, but thats no longer an option ($$$). They're all really close to being the same... but a little different. Headers are dry SS. Looking for max HP, the lower in the RPM range the better.

Donny at Herbert cams ground me a custom roller for $200.

A Power adder is NOS, Turbo, or Blower. Usually with a power adder you want a wider lobe separation to take advantage of the increased torque. Personally, I ignore that, and set it up for naturally asperated, and figure I can bump the boost or increase the jet for more power.

The lower the RPM the shorter the duration. I usually pick the duration based on the RPM I want, then get the max lift I can find out of that. If you go for maxpower, you also want to compare the adv duration and the duration @ .050. The smaller the difference, the steeper the ramp, and the more power you will make.

Lift and ramp = HP (higher and faster is more)
Duration @ .050 = RPM range (lower is lower)
lobe center = Curve (higher = flatter)

That RPM range you are picking is a 3500-7000 range, give or take on the grind and lobe separation (previously covered).


I personally like the tight lobe centers - the powerband is narrower but higher. For me (and YMMV), I know my jet will be running 3500-5500, so having a torque curve that works from 2800-7500 really isn't optimal. I'm giving up peek HP for a wider operating range that I wouldn't be using.

Given you want the power band a little lower, I'd probably go for the
260/270 @.050
680/680
110 lobe sep.
110 centerline

 

Your knowledge never ceases (sp?) to amaze me speedy.   

   <----- you   me---->    

x2

On the same topic, lobe seperation and lobe centerline, what do those two play in the role of octane requirement for an engine with all else being equal?

On the same topic, lobe seperation and lobe centerline, what do those two play in the role of octane requirement for an engine with all else being equal?

I'm feeling the love - Thanks!

I've had a bunch of wine, so I probably shouldn't answer BUT I'll try anyway...


First you have to understand what lobe separation and lobe centerline is and that they are different.

The centerline is just that, the center of the opening and closing of the valve. You have one for intake (ICA) and one for exhaust (ECA).  It is the average of the duration for the most part (yes there are asymetrical cams,but not tonight)

Lobe separation angle (LSA) is the intake (ICA) and the exhaust (ECA) averaged.

A cam with a 103 ICA and 117 ECA has a lobe separation angle (LCA) of 110 degrees  ((ICA+ECA)/2).
BUT So does a cam with a 110 ICA and 110 ECA, that is also a cam with a 110 LCA....

Anything that causes the intake valve to shut sooner will cause more dynamic compression and a more likelyhood of detonation. Basically, it is the ICA and intake duration that determines how friendly the engine is to gas, not the LCA or ECA.

If you compare the same cam with a 110 LC but with the ICA moved around - the one with an ICA of 103 will ping over a cam with an ICA of 114 because that intake valve closes sooner. However, it will make more power if you don't ping. When you advance or retard a cam, you are changing the ICA, not the LCA.

A 10:1 engine with a 280 degree cam will run on regular all day long, while a 9:1 engine with a 200 degree duration cam will have a hard time with even premium.

Remember - if you have a pinging problem - go BIGGER!

Hopefully I was clear, didn't miss anything, etc. Now, back to my Wine!