Allright, I keep hearing everyone say to get a custom cam to match your heads, but they never explain how exactly besides the ole "ask the guy who did your heads" comment, and I KNOW there is alot more than just flow numbers to it (dynamic compression, port velocity, displacement, desired power range, etc...)... So with variables such as these, how exactly do you organize a custom cam to match? Maybe a few examples, like a street/strip NA 350, a track NA 383, you get the idea...

BTW, I'm not trying to figure this out for the particular heads on my car (their stock anyway), just trying to learn for future reference, Thx a bunch.

 

anyone?

 

I guess no one knows...

 

I think matching comes in when you are trying to match parts... cam and torque converter. Cam lift and valvetrain parts etc. In my mind, it's either lightly ported, medium porting, or hogged porting depending on your combination to go along with light, medium, and big *** cams. I mean I don't think there is really much to match. You set your goals for the engine and design the cam specs to what you want. The heads themselves are just for getting air into the cylinders, however the valves, valve springs etc. all have to be matched for the combo to make max power and work correctly.

 

Yes... but you want to know what cam your using first before getting the converter/Valvetrain to work with it...

I'm looking to get into alot more detail than "Light" or "Big-assed"

I'm trying to stay away from... "Well you have good flowing heads, here's a big cam off the shelf that should work for most good flowing heads..."

Example...

Say someone goes to an engine expert that designes cams and he wants his 350ci motor to peak anywhere in the 6000-6300rpm range with as much power as possible naturally aspirated not caring about low-end tourque, just how would someone like him figure out some specs that are close using variables such as these...

Bore 4.00
Stroke 3.48
Head Flow #s xxx
Runner cc's xxx
Port velocity xxx
Valve size xxx
Static Compression xxx
etc. etc. etc... You get the idea.

I don't think there is a "magic formula" that makes the most power, just trying to find out how would one make a custom more suitable to a certian pair of heads than a cam off the shelf.

Thanks for trying though, it's more than anyone else has done so far.

 

One method is to use a fairly sophisticated engine simulation program, with an experienced operator who understands your desires. Depending on how much time can be devoted (read that $) to the simulation, any number of lobe profiles and phasing can be tried. There are enough cataloged lobes that rarely would a new lobe need to be designed.

I've seen over 200 combinations tried for a single engine. That's extreme, but for your example, 10 tries would probably get within a few %.

The down side is that you need very good flow data for the head/manifold combination, and valvetrain parts cost for ultimate performance could be high. All those factors have to be addressed.


My $.02