Like this:
http://media.putfile.com/Exhaust-26-29

Nice, couldn't ask for a better description. BTW, that side exhaust looks rediculously good!!!

Question: It was implied in this thread that the XE268 and XM 270 fall off in power a little too early (4800-5000rpm?)

I see one refernce to heads being used (ported 300hp crate heads) on, I think a 5.7 while just one other but on a 383cid with Vortec heads.

Reason for bringing this up is I'm trying to see a real trend. Trying to see if it is more a cyl head and/or exhaust issue. Oh, yes, adding cubic inches can of course bring this top power rpm down.

The smaller 268XE has proven to make more power higher up in rpm on dyno and in car than what is presented here in boats. However, better cyl heads are typically used in my studies.

So, I'm just trying to pull this all together.

It's all about real, usable data so we can all move forward on things.

I have ported vortec heads with the xm270 and it pulled strong to 5300rpm in a 355ci.and a quicksilver 21p prop(22' boat) with a 23 mirage plus it pulls hard to 4800(61.2 gps)i don't feel the cam is falling short on power

I plan to clean up the ports a little in my heads (vortecs on 383cid) and port match the intake as some of my mods for next season hopefully that will help hi rpm breathing. I have always been of the understanding that great heads with an ok cam will make more power than a great cam with ok heads. I think my heads are the limitng factor in my combo right now, especially considering the increased displacement.

Yes, but in generalized terms. Really what you are comparing or saying when saying "good" "bad" or "mediocre."

Vortec heads are really good, but this is comparing against many OE GM small block heads and on what application, of course.

They are quite good on a marine 383 build up as you've seen, but, if trying to get some more rpm they can be a little resistant because of runner cross sectional area and flow rates.

They are really best sized for a stout 5.7. Again, stock and even with a little bowl and clean up work, hp seems to be limited around 410hp or so with mild compression. A larger cam to make more hp thru rpm typically falls short and maintains same hp # but loses some low end torque.

I believe if you are trying to juice the 383 a little more with some more rpm than having a pro porter that does many Vortec heads do the work or start thinking about a larger head. Something in the 185-200 runner size.

What do you think of the Edelbrock Etec 200? They have 200cc intake runners, and 64cc chambers. I like them because I can keep my current 8 bolt intake and centerbolt valve covers, and they are light. I know they are aluminum, but I have closed loop cooling and I only see lake water.

Haven't used them. I hear they are okay.

The new AFR Eliminator 195 would be as good as you can get for your motor. I don't believe (but I'd check) they can be set up for the Vortec intake, but they will accept the centerbolt covers.

You keep mentioning 114LSA. Are you sure ? Comp's XE use 110's and XM's use 112's .

My current cam is 114. You are right, the xr276 is 110, and the xm276 is 112. I need to find the fine line betwwen more power with better hi-rpm breathing (which the etec seems capable of, bigger intake and exhaust valves along with bigger runners intake and exhaust) without making too-much power (I know, sounds crazy) because I am running an alpha. I know going to 200cc wil cost me some velocity, and therefore torque, but I am hoping the light hull weight along with the extra torque a 383 makes will cover some of the potential loss. The etecs will cost me about $500 less (price difference + cost of new intake) and that will help offset the cost of having inconel exhaust valves put in.