Cam Choice revisited - starting point

[bill_396]

Reading "cam Choice" below has me wondering what do you use as a basis when you are picking available lobes off a chart for a custom cam?
My combo is as follows:
428 "C" block .025" over, decked and line bored (guess deck will be near 0)
SRP flat tops (-5cc relief)
4.25" Scat cast crank (to yield 461 cu in)
Scat H-beams
Blue Thunder small bore heads, having chambers profiled, minor port work as needed - targeting around 80cc but as req'd to achieve  8.2ish DCR
solid roller cam
Victor Dominator
Hooker race headers
68 Mustang with wide toploader and 3.91 at this time, will go deeper if req'd
The application is mostly radical street, 6500 rpm max. Because I have not finalized my combustion chamber size I am really not locked in to a certain duration to achieve my desired DCR but where do you start? thanks

[afret]

One thing you might keep in mind is what "family" of lobes you choose.   If the car is a real street/strip car, stay away from more radical and aggressive lobes which require a lot of spring pressure in order to take the engine up to a decent RPM and stick with street roller or endurance/marine type lobes.  You can go to bushed lifters but I think other weak points of the lifters will begin to show up with extended street use if you use overly strong valve springs.   If you stay under around 650 lbs open pressure or so, things might last longer. 

[jayb]

There may not be a precise answer to your question.  But when selecting a cam, I usually start with a horsepower target.  Do you have one for this build?  A strong FE will usually go in the range of 1.3 - 1.7 HP per cubic inch, depending on how radical you want to get.  Let's say you want to make 650 horsepower, or about 1.4 HP/cube in your case.  From experience with my dyno mules I know that a 266@.050", .700" lift lobe from the Comp Xtreme Street roller series (lobe # 4878) will make around 675 HP on a 482" stroker FE.  I'll be that same cam would do 650+ HP with your combination.  Pair it with the same lobe, or else the 4879 lobe, on the exhaust side, and run with the Comp 943 springs.  I've had good luck on the street with that particular combination; in my 511" FE with the Victor Dominator it made just over 700 HP, and lasted for 10K street miles (before I took the engine apart again  ).

Hope that helps - Jay

[afret]

The 930 springs might be a little weak.  The 943 or 955 might be better depending on what installed height you need.

[bill_396]

Thanks guys, that was the start I needed. Now I can do some better work on my DCR calculations.

[jayb]

The 930 springs might be a little weak.  The 943 or 955 might be better depending on what installed height you need.

My bad, I meant to say the 943 springs.  Oops   I will correct my original post...

[bill_396]

Using the lobes Jay suggested, advanced 4 degrees, it looks like I don't need to have my chambers cut. 11.64 static down to 8.25 dynamic, wow!

[jayb]

"I love it when a good plan comes together!"  (George Peppard, The A-Team)