340 Cam, rocker, valve spring questions

Also for the good of the group.

I see a lot of people just throwing high lift cams in their setup. Seems to be a general consensus that the larger the lift the better the flow and performance. Couldn’t be further from the truth. Over camming an engine will kill it. Some say to pick the cam first and build the combo around it. You could, but I choose to pick the heads and build around that. Reason is you are limited by what your heads will flow and at what lift before you get into port stall etc. What I meant above by .500 for your combo is, current flow bench results show that the J head flows best at .500 lift, un-ported. If you go over that you are actually stalling the port and reducing velocity, which reduces the over all flow. Now, let’s say you have a set of heads that flows 360cfm at 600, 310cfm at 500 or 340cfm at 700, then you can see you would want to be right at .600 lift, no more no less. Same with the J head, UN-ported flows best at .500, heavy port flows best around .550 to .570 depending on who did them.

I forgot to mention above that degreeing the cam can move your power band up or down. Example let’s say you went with that 107 LSA cam. You can move that narrow power band up and down. Adv 5 degree from centerline would make your torque come in early and run out early, Ret 5 degree from centerline would raise where the torque came in at and run out later. Some off the shelf cams have advance ground into them, so you must check the cam card and installed centerline when you install.