Humm, no, more like, don't build a street performance engine with pro stock heads. If you have a set of indy heads to build with, and decide to build around the head, do so accordingly. Don't build a mileage master with throttle body FI and emmissions in mind.
(OK, extreme example, LOL w/me, but that is where I was going with it. )
You can get roller rockers for the Magnum head. An extra expense that is worth it? Only the pocket/wallet will say. I like to get the cam lift I want rather than use a higher ratio rocker to get there. But that isn't allways the case...as in my current case (cam in use) though I'd rather have the cam than a higher ratio rocker myself.
But in this guys case, a choice between heads and there rocker ratio differences... a higher ratio could be a benifit. So far, his build perameters are a unknown and your assuming and pushing the idea of a higher performance build than anyone else on here assumes. Your going right to the max and extremes of things. Point in case is;
Guide wear. Any head will have it and more so and quicker in a higher HP build. High performance = high mantaince. Is this guy there or not?
A higher port roff is allways perfurable. How is the port relation between heads vs where they sit in relatuion to the exit at the valve vs angle and bend?
Just because head Z has a higher port doesn't automaticaly mean it will out flow head P with lower roof hights. Romove your thinking from a MoPar hea and look at other manufactures heads and there flow rates vs port location and relation and cc amounts.
In the big picture, it's small potatos. Something to avoid, sure. Why is it other manufactures have a semminly not a care in the world about it and there engines still make big power? Valve shrouding and it's effect is over rated like a scared kid and a VooDoo doll.
But again, if you can avoid it in a power house build, do so. Will it make a hge difference on a 275 HP engine? Maybe so, but I think the peanut crumbs that everyone is worried about is crazy.
It's not poor blue printing, it's poor thinking. Blue printing has nothing to do with this.
You wanna run the air fuel through the head curve passed me again?
Run this pasted the OE posters build and not what your thinking of. You keep beating this horse half to death when the unknowns are still lingering.
If I follow what your saying like a blind idiot, and you know I'm not, a set of INDY heads should be used on my daily driver for mileage reasons.:-D
Rob, we [Dave & I] were comparing old to newer magnum stuff-stock and modified, no body is lost here, or at least not us 2, you did read 'low lift flow', right? so you should know the lift range were talking, right?lol
You are now using the far end of examples with the pro stock head mention...You should know the lift range we are revolving around-hence all the low lift flow talk. You just generalized even more by relating your example of street motor 'whatever cid' with prostock heads [only fit hemi's] to a small cid/ or low rpm range, but it's because your efforts are to catch me slippin here somewhere, or is it not?
I'm not explaining every aspect here, too many variables, being a tuner I know this but I'm not trying the write a 'how it works' book
btw ...more lift is HP, nothing wrong with adding higher ratio rockers and making more power, even in a head that stalls out just below the increased max lift 'say went from .500 where peak flow is, to .530' from the higher ratio adds power because you just lengthend time for flow and opened the valve to the peak flow@ it's lift range 'by virtue of faster/higher lift' because you now put the peak flow @ lift in/closer to the longer duration opening/closing cycles of the cam used.
You can take a head that stalls at .450 and stick a .557 cam in it and make more power due to the add'd duration for flow at peak lift, could even go bigger to an extent.
If you run over .500 lift on the street and expect longevity in the guides by avoiding too much side loading, you need to run some roller tips, can do with out=yes, will it last and not eventually ruin the valve job=NO.
btw, how many times does someone ask this 'whats better' question with nothing else to go by?
Thats why you get the all or nothing response, cause thats all you can give, which I think we've covered most-low lift flow-head features/benefits, which will actually make the diff and what has the best potential...and so on.
Valve shrouding....can be worth 7 or so cfm depending on the valve size and relation to the chamber wall.
Other manufactures? try most all stock stuff, let alone compensation in flow to overcome any significant/insig flow loss.
Car companys are not building around this issue let alone the idea of obtained 100% VE and HP per cid, kinda how you can raise the hp of a sb dodge, or whatever, a 100 hp fairly easily with bolt ons & in's and piston swaps etc..know what I mean?
blue printing go's beyond thousandths and cc's.
when you house was build don't cha think they had standards for cooking range size/power requirement?, types of sinks for the time, which pipe to use galvy/copper?
btw, on the roof height deal...ha, ok...if head Z [which better be a mopar sb head cause thats what 'we' are talking about] has a higher roof and also has a good workable short turn over head D-... Z wins in the flow/potential flow arena.
something you are missing is that , it ain't about the 290's a j head can flow fully done, it's the fact that it still flows 200's at .300, 240's-250's at.400 and 270's at .500....
what about a prostock head??
or for that matter wether the op is doing mild or wild on the street?
That head will work everywhere on a mid sized 320+ inch motor
and about the horse and the beating 'n such lol, Someone said the magnum head was better than the j head in stock and modified, or at least they have not come out and said any different. thats no true and so I will smash this horse into puree if I have to.ha ha
I don't always take/read posts for all the tone the poster may have inserted, so maybe I'm taking this wrong 'what u are saying to me' that is..
But I know you know what I meant, it's frustrating though when someone won't be or isn't on the same level as to understand the realm in which I'm speaking of, thats where we get mixed up.