I know this is a broad field but and there are many variables, but ballpark speaking how many tenths and MPH are gained from a simple aluminum head swap?
Indeed. It's hard to say what the heads, themselves, will net you because you're almost required to do everything all in one shot to really make it work right. Opening up one part of the system while the rest of it is a bottleneck can make for some really weird results - losing torque and gaining HP, or vise-versa, bogging off the line, running lean/rich, pinging, whatever - so about the only thing you can really gauge is to look at a stock longblock versus an average H/C/I car ... which can put you anywhere from 250 to 300 total HP (or better), from the setups I've seen listed on here, depending on what else you have going with it. (Obviously, if you have a full exhaust and some other bolt-on goodies, you'll do better.)
Besides ... what's the point in running aluminum aftermarket heads on a stock intake and cam?
Not to hijack the thread but my motor is completely built except the heads. How much do you guys think I will gain? The cam is a TFS1 and the intake is a weiand stealth. The motor makes 270hp and 330tq at the flywheel.
Should stick you at 280-290 rwhp pretty easily, so maybe a gain of 50 hp or so? There are so many variables to say what one thing will do alone, but your best bet is to do it, and see what happens!
yea, def depends on the car... My previous motor had those heads, box stock 6037's with a cobra intake, and a pretty simillar combo (of course without the blower) and it put down a tick over 300 hp, and close to 340 ft lbs at the tire, the car went 112 mph all day long full weight. The performers are a strong head if used in a good combination... but like everyone else her has said... It takes a really good combo, and LOTS of tuning to get there. With a fully built motor, and a decent H/C/I 300 rwhp is easlily attainable these days...