I have been ranting about how critical it is to know how to use SCR's and DCR's formulas for cam choices.Richard on another site gave this explanation which I want to share because I think it is well written:

You cannot reach out into thin air and choose a camshaft for a motor. The cam is not a stand-alone piece, it must be matched to the static compression ratio of the motor in order to close the intake valve at the proper time to make the proper amount of cylinder pressure that will work with the fuel you plan to use. The first question that any cam tech at any cam grinder you talk with will be "what's the static compression ratio of the motor"?

The scenario can go wrong either way:
1. You have a low compression ratio motor and choose a killer cam, long duration and high lift. You're looking for that Ricky Racer rump-rump to impress the geeks down at the Sonic. The intake valve closing is extended to a point where the piston has pushed most of the intake charge back up the intake tract by the time the intake valve closes to begin compression and you are left with low cylinder pressure and a weak motor that won't pull the hat off your head.

2. You have a high compression motor and choose a wimpy cam that you think will be just about right for a daily driver. The intake valve closes too early, creating more cylinder pressure than you can use with pump gas. The motor rattles like a can full of marbles from detonation and pretty soon, you've broken all the ring lands off the pistons.

One more time....YOU MUST KNOW THE STATIC COMPRESSION RATIO OF THE MOTOR IN ORDER TO INTELLIGENTLY CHOOSE A CAM FOR THE MOTOR.

And then this article:

http://www.chevytalk.org/fusionbb/sh...php?tid/92966/


Lastly-if you think your money up by using a non roller block you should consider what your giving up:

http://www.enginebuildermag.com/Arti...oller_cam.aspx

Thing is it does seem like alot of details.Especially in the DCR.But it is those details that in the long run is going if applied correctly is going to give the best outcome and truly save you money.

 

As long as the cranking compression is between 120-200, you can drive it on pump gas. 120 will drive doggy, and won't give good MPG, and will want more gear with a looser converter but will never need more than 85 octane. If you have a mystery engine, it's not too hard to get your baseline pressure, then find the intake closing at 0.050", using a degree wheel and a dial indicator. We'd all love to have "ideal" builds, but most of us can settle for something that's never maddening. The more crucial issue is matching everything as best your budget permits. Sometimes playing with the cam isn't the next step, either for appropriateness or for the budget, but sometimes we all get blinded by lust, hung up on a strong desire. Better to be cranking 140 with everything else ideally matched, than to be cranking 190 but nothing else matched at all. SCR and DCR are both just tools to help us predict cranking PSI, which is just a tool to help us with tuning and octane selection. Knowing your exact SCR is necessary to find your theoretical DCR, but finding the SCR is not worth the cost of a gasket set and a weekend of labor. Don't invest in tools you don't really need. Just rent the compression tester.

 

Applied formulas are a cost savings.Do-overs will always cost you more.A dial indicator for the cam with a magnet base is the same one for use in deck height,piston cc's etc.It's all about choices with those formulas in advance of a purchase.Agreed,cams mismatched cost about the same as ones that are correct.And to reach out for the cam solution to solve all your problems isn't a good decision.

Maybe for me one of the most disheartening things for me to read about is how much people are not willing to "pay their dues" to build it right.How they can't live without their cell phones,texting,cable/dish TV's etc.Yet they whine about a budget for a build and take compromises way too far,then complain about how it doesn't work right.Or don't know what they are missing if it was done right.The worst of the worst is someone wanting to play games and make it sound bad,but it isn't.Head games.