FiveLiterRiceEater

i know this topic was beat to death a while back but i cant remember most of the threads and dont want to search for them.

I'm getting my shortblock within a week and i'll be buying parts shortly after, and a cam is high on my list. What I want to know is how i can pick an off the shelf cam that will be good for my application. What other aspects of my engine will i need to consider when i buy it. I would much rather prefer to get a custom ground cam but i dont think time and money are going to allow for this. and im still unsure of some of the stuff ill be putting on the engine anyways.

I know that a lot of lift isnt always good, and that it can result in a power loss. but how much is too much?

what kind of duration numbers would cause more low end and mid range power vs high end?

is it better to have more intake duration or more exhaust, and what will having more of one of the other cause?

is it better to have a lot of lobe seperation, or should i stick with something closer together?

88stangaruu

Gonna need to know alot more, what heads, exhaust, intake, etc.

Twister

simple, call Comp Cams

FiveLiterRiceEater

ok.

331 block.
afr185s
Holley Sytemax 2 intake with a 1 inch spacer
75mm tb
80mm maf
equal lenght shorty headers
24# injectors

it'll be a 10:1 compression engine also. anything else?

Dath

Should put some thought into this before you pick a cam. Pick a cam off the shelf that will allow you to enjoy the car as you upgrade it through the different stages (months, years, decades), and then get the custom ground to fit your car when you have it where you want it.

88stangaruu

I would try to go custom cam if i were you, thats going to give you the most power, your already spending the money, mind as well get one now. But if you dont want one, go with a Trick flow cam, theyre really nice cams, good power bands, split duration, etc. But custom cam is the way top go definatly.

sgt_pepper17

Well here's the lowdown. I'll let you know some of what I know and then if you have any questions just ask.. I've read this stuff until my eyes have bled and I've also tried a few cams in my cars as well as my buddies cars.

As for duration, you need to know a few things here. I'm assuming you have a roller motor if it's a fuely btw... You have a stroker motor. This means that the motor is not going to be geared for RPMs but, if it's a stroker, it'll be built with that in mind because most 331s and 347s are built to turn around 6000rpms. Basically, you can get away with more cam because the extra stroke will give you the bottom end that you wouldn't have in a 302. You definently want a split pattern cam if you're running stock casting heads. Ford's small valves make good use of a split pattern camshaft. As for centerline, the smaller the more aggressive idle. Anything that is 110 or 112 will be good on the street and will run very well w/o nitrous but will still run fine with it. Centerlines in the 114 and higher range are considered "lazy" because they don't run very well without nitrous. Anything smaller than 110 will have a very aggressive idle and because I've never really run anything like this I don't know how it will affect performance. As for lift, no cam will have too much lift. Generally for a cam in the 230 duration range at .050 lift will have .500 or more lift with stock rockers. Be careful because a cam with much more than 230 duration may need a vacuum canister for power brakes. You can get a cam that big and still be okay on the street with a gear (the added stroke will help out a lot too) but like I said, much bigger and you're looking into a vacuum canister for braking.

Here's the breakdown (a word most commonly associated with chevy's) of duration and lift in a cam. Because the exhaust valve is smaller, more duration and lift is required, in general, to move the same amount of air through it as the intake side. Cams in the 204intake 214exhaust range will have lots of bottom end and some good bottom end but will generally faid out around 4500 rpms. Cams in the 214intake 224exhaust range will have good bottom end, very good midrange, and more top end fading out around 5000 to 5200 rpms. Cams any bigger will generally be geared towards mid range to top end. You can offset this by adding stroke to your motor, or by lowering your rear gear ratio, or better yet, both. When you get a cam with lift in the uper .400 range and definently in the .500 range you need to get better valve springs to avoid coil bind and to avoid floating the valves at rpms in which the cams are meant to run in. Generally the cam manufacturer will recommend springs and then just buy springs similar to that or the springs they actually recommend. It is crucial that you do buy springs though... do not forget this...

If I were you I would call the Comp Cam "Cam Help Line." Their number is 1-800-999-0853. They've always been helpful to me.

tinman

I'd sure buy lift before I'd buy duration......
See prevois post by SGT....