Exhaust valve lift is .479" inch (12.17mm) (net is less .006" inch (0.15mm) lash), @ .050 (1.27mm) Lift, up from .459" (11.66mm) for the LT1, and for intake is .476" (12.09mm) (net is less .004 (0.10mm) inch lash), up from the LT1's .447" (11.35mm). Duration is increased slightly on both exhaust and intake. 203 deg. Intake, and 210 deg. Exhaust. 115 deg. lobe centers. 1 deg. Retard. Increasing overlap significantly, allowing elimination of external exhaust gas recirculation. The overlap area amounts to internal EGR.

So now where do stock heads stop producing power? Example. Do heads stop flowing at .500 lift? I mean do they make no power above a certain number?

So if I go with an aftermarket cam say the XE 224/230 with a .535 .544lift with 1.6 RR's am I making the best use out of it with stock heads. Will the heads flow to where the cam is maxed out on lift?

ahve I explian myself clearly or correctly?

Interesting question. However, saintxx (along with at least one other) made good power with the 306 cam. Saint trapped 115mph, so I think its safe to assume he's making good power (350-360rwhp). A dyno graph would be nice to show what his curves look like. For once in Cz28.com history, this post might be better off in "Advanced Tech."

The more I learn about cams and how they work with engine combos, the more I realize I have no idea what I'm talking about .

Ryan

I believe stock heads "peak" at ~ .500" valve lift and fall off a few CFM at .550". There is definitely a limit th how much lift you want to run on a stock head, but the heads still flow decent (relative to their peak) at .550"+. After the head flow peaks, you will lose some port velocity and some say you don't want to go past peak. The way I look at it is the more lift you have, the more air can enter the cylinder over the entire IVO/EVO duration regardless of the cylinder flow #s after peak. This obviously has a limit, but I've seen it proven over and over. The stock heads like a big cam...ie, cc306. The ports don't flow all that well, so having the valve open more/longer allows more air to enter the motor over the cycle - which in turn brings more fuel/power. The problem with these bigs cams on stock heads is the fact that you will lose port velocity and in turn lose torque. You will want gears if you have a large cam on stock heads.

When I had my heads ported, they game before and after flow charts. If I can remember correctly there was about 5cfm difference between .500 and .550, max flow was around 212cfm or so.

At .600 they began to fall.

People tend to forget that Lt1 heads are among the best flowing (small block heads) from the factory, for the exception of the LT4, and LS1 family. Before the LS1 ever came out only the Vortec and the Lt4 flowed better. The Vortec heads fell short in the exhaust side compared to the Lt1.

Im set-up now with 3.73 gears, LT1 Edit, Hooker Shorty Headers, 3000 TQ conveter and the items neede to run a "bigger" cam. Ie 10308-1 Crane Springs, 1.6 RR's, etc. Im only missing the cam, lifters and a new timing chain otherwise I am set.

Im just trying to determine for example if a XE 224/230 with a .535 .544 lift or the XE 230/236 .544 .554 are not the best cams when running stock heads. If the best power is made at .500 and falls off at .550 then maybe I dont want the XE 230/236 or the CC306 cam. Maybe the "biggest" to go would be the XE224/230 on the 112 LSA.

Opinions?

Hows things in the Valley? Lived in Brownsville for 3 years. I think I may have been the only coconut there

Stock heads like 8-12+ of I/E duration split. I don't think the XE grinds are the best grinds for stock heads. A CC306 may be a little much in an auto, but something similar would probably work pretty well. I would think something in the 220-225/230-235 I/E range and ~ .550" lift would work well with the stock heads. A cam like this would also work well with heads in an auto. My CC305 works pretty well on the stock heads - when I get heads, I will be going with a custom grind somewhere in the range I listed.

I have heard that the XE grinds are a little more forgiving on the valvetrain than say a CC305 or CC306. Maybe I am wrong. Could someone correect me if I am speaking out my dairy are.

I was told many times be different foks that the XE224/230 112 LSA is the cam to go with stock heads. Some Mentioned the XE 218/224 as another option..

Does this cam maybe make sence to you. a 218/230? Or is this just silly? Think about the stock heads VS the intake and exhaust sides here. benifits or just silly

I would think the XE grinds would be harder on the valvetrain due to the steeper ramp angles. The XE grinds will make more low-end/mid-range power than a cc305ish grind. On the same token, you could go with a slightly larger I/E split on a XE type grind.