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Discussion Starter #1
i'm planning on staying NA and was wondering if the SHM 4V heads would be better than P&P'ing, camming, and valving the stockers that i have on there now.

does anyone have experience with just the heads on a stock bottom end??? pros and cons if any
what kind of power improvements are you seeing???
how does it affect the power curve???
 

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It depends on how far you go. If your talking a race engine with high compression, very tricked intake, Stage 1 and 2 or just stage 2 cames, and high RPM's, then you'll want to open up the ports a good bit.

If your talking a street car thats daily driven or close to it, and your running a stock intake, etc than I recommend spending a lot of attention to the bowl/valve area. I would also just recommend removing the rough casting, and smoothing the runners. You want to increase velocity in this type of application. The stock heads can flow good numbers to support high 11's at 3300 pounds or about 325 rwhp. The trick is to get the air in and out faster and increase the velocity.
 

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I can't explain the concept as well as Dave, but when I ordered my SHM engine for mostly street use, they suggested the stage 1 heads for my use, which does not have much more than a good clean up. (and i was willing to pay for stage 2)
At the time I thought more head work would be better, but they convinced me I would probably lose low RPM power with more head work (for my use). They explained you do not put 800 HP capable heads on a 575 HP engine. I now believe they are correct for when I dyno'd 550 RWHP, my RWTQ was 460 thru cats, which is good TQ for that power level.
The key is to have a balanced system from intake to exhaust , each part designed to work optimally with the other parts. MHO

Sorry...I know that is not your question, and you already know this. I just inserted this for any others thinking about lots of head work on their 250 RWHP engine.
 

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Discussion Starter #4
I eventually want to get to ~350 RWHP NA on a very streetable car.

So the stock heads with a good P&P (without valve work) is good enough for 325 . . . so the SHM's are just stock heads with cams and a P&P right? so if i get SD Wheeler to work his magic on my heads, valves, and intake - all i'd be missing from the SHM combo are the cams???

one thing i'm concerned about, if going this route of modifying the stock heads, are the valve springs and valve guides. are these (or other parts) points of potential weakness that i should get addressed while i have it apart?
 
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