Streetrod's version of "top out" is discussing flow potential. Scott's version apparently concerns amount of valve lift before the retainer meets the valve guide boss. Let's discuss flow first. While this "Fletch" person shows that his measurements are taken at 28", we don't know what machine he was using or what size bore plate was installed on the machine. Take a head that flows 195 with a 4" bore plate and you can "show" a flow of 210 by using a larger bore plate.....say 4.100". Less reputable shops were doing this years ago when the general public first caught the "flow bench number" insanity. But I digress. If you look at "Fletch's" numbers on the GT40P you will see that it did not gain any appreciable amounts from .400" lift to .500" lift on both intake and exhaust. Primarily the intake. So, from that point of view you could say that the head "tops out" at .400" lift. So, do you "cam" the engine for only .400" lift or do you stop at .500" lift? Common sense would dictate installing a camshaft that bumps right up to the .500" lift mark to take full advantage of the heads flow potential. Here's the really neat part that most people just flat can't see: Yes, it flow "X" at .500" lift.....but what does it flow at .200" and .300" and .400" vs. another cylinder head? Remember, every time the valve goes to .500" lift one time, it passes .200/.300/.400 two times. Lesson: peak flow is nice to look at but it's what's underneath that's the really important part. While all of this certainly looks nice on paper and lends itself to plenty of speculation on cylinder heads vs. performance potential............I've never seen a flow bench or a dyno win a drag race. Period. How would I cam an engine with these heads? Depends on the rest of the equation. And yes, that's my final answer. Now....Scott's dilemna: You have to measure the total travel of the valve with a checking spring installed. Insert the valve into the head, add a checking spring, install the retainer and keepers. Next, measure the total travel of the retainer from "installed heighth" to the point where the retainer bottoms against the valve guide boss. Of course, this can be adjusted with machine work if necessary but typically these heads will not be used with a camshaft capable of bottoming the retainer. What you'll need to check once you have the correct springs/retainers/keepers is the installed height (to make sure it's set up correctly according to the spring specifications) and the coil bind (total travel necessary to "stack" the spring coils into a solid block). Hopefully, you have enough travel to reach full valve lift well before you run into coil bind. For more information on camshafts, degreeing cams, setting up valvesprings, etc, etc, please see Comp Cams website. You'll find excellent technical information that should be good reading for several hours. Class dismissed.
Oh yeah, Scott........."Stage 1" from this guy means: Stage 1 - heads that have minimum clean up work to improve the volume of flow over the as cast condition. Typically heads in this category will have the bowls blended, gasket matching done, and a good three angle valve job. Taken directly from his site.
Going to chime in here, I have a couple thousand miles on my new setup. I'm running an '89 roller block, .030 over with a TFS Stage I. I have stock E7TE heads with 1.7 roller rockers and upgraded springs. I also have a 3k stall converter. It's the converter that makes the car for me, the trick flow cam comes in late in the rpm band and the converter allows me to get there. With reference to valvetrain. I have 6cc reliefs in my pistons just for insurance on my valves. I also have 300+# open springs (150+# closed) so I don't have to fear dropping a valve. I am using crane pedestal mount roller rockers and stock length pushrods with stock lifters.
