cam spec FAQ??!!

jpnovak · 09-27-2004, 07:33 AM

Based on some of the information that was mentioned in my build thread for a 3.2SS a few things were mentioned regarding cam specs. I was wondering if some of the knowledgeable members could write up a FAQ regarding different cam specs and what they mean to engine performance.

I am looking for Cam spec 101. Maybe some statements about general engine performace for a given spec. For example.

What effect does lobe center have on torque curves?

Does more lift move the torque curve up or down in the rev range?

How does increasing duration affect drivability?

When does ramp rate affect valve train strength?

Does cam performance change with engine stroke or bore? (effect of feeling mild for bigger engine)

Feel free to add answers, questions, and links if already provided elsewhere. I am looking to put all this information in one thread.

jluetjen · jluetjen's Garage

I've got one in process already which Camgrinder gave me some input on. I've got to incorporate his thoughts and then I'll post it here.

jpnovak · 09-27-2004, 11:50 AM

Sounds great John, I can't wait.

BURN-BROS · 12:01 PM

http://www.chevyhiperformance.com/techarticles/95298/index2.html

Here is one about overlap and header length.

and another

http://www.chevytalk.com/tech/101/Cam_Theory.html

camgrinder · 09-27-2004, 09:44 PM

Valve lift usually increases the cylinder head breathing at every RPM. Going from a .440" valve lift to .500" lift does not affect the torque curve like adding duration.
Adding duration will move the power band up, this can cause low speed driveablity to suffer.
"Ramp rate" is being misquoted. The term "ramp" is used to describe the clearance ramp, which is the area on the cam lobe used to preload the system on opening, and seat the valve on closing. Usually the ramp is measured from .008" to .014" lift. In this range the valve is kept at low speed.