I was running 13.10's at 105 with untouched 1970 351W heads on my 302 (mild build). Should have been close to 300 hp. When I switched heads, it took another 8 tenths off, lol, but, the iron heads were making good street power.
Heat is lost power. internal combustion engines are onyl around 25% efficient because they lose so much of the energy they creat to heat instead of rotating force. Heat is not power. Because aluminum heads disipate heat faster, they also allow for a cooler engine, which can then be translated into more power.
That's why I always run with the coil disconnected, so that the engine won't be able to create any of that nasty heat
Sorry, but you got that backwards. Combustion around top dead center increases the temperature and therefore the pressure in the cylinder, which pushes the piston down. The higher the temperature, the higher the pressure and thus more power. Cooling reduces the temperature and thus power.
However, a hotter running engine also heats up the mixture, making it less dense, thereby reducing power. You could say that a hotter running engine inducts less air-fuel mixture, but runs more efficient. If the cold running engine looses 5% efficiency through cooling, but inhales 7% more mixture, it will produce more power nonetheless.
you botched up your own logic on that one, lol. Cast iron heads retain heat, thus, making a (very slightly) more efficient engine. Heat, in an internal combustion engine, is power. Aluminum heads shed heat faster, so you lose some efficiency. Problem is, nearly all aftermarket aluminum heads flow more air than cast iron heads(aftermarket or otherwise). You will gain power by switching to aluminum heads 99% of the time. You could port some world products heads, but then you have more cost and more weight, but still less performance than some mildly cleaned aluminum castings.
As for the original post, 300hp is easy with a 289 or 302, and does not require aluminum heads. Check out a set of GT40's or early 351W heads. The edelbrock perfomer stuff is fairly outdated by todays standards too, you can gain some power by not using the "package deal".
I am not saying slap a set of stock heads on and it will work better than aluminum. Hell I am not even saying dont run aluminum, I dont see them very beneficial. Its a 300 horse daily driver, why drop all that money on aluminum heads? Build a nice set of heads matched to your intake and exhuast, aluminum heads arent. we had a nice 331 with windsor seniors and it dynoed almost 500 horse. Took a shelby over 170 miles an hour
unported windsor sr's will not support 500hp, they only flow 220 cfm. Ported stock heads can do that. For $200 more than the W Sr's, you could have aluminum heads that flow more and weigh less. Sure you could port the W Sr's, but then you have more cost than whatever aluminum heads, and you still have 50 lbs of extra weight. I just don't see the point in aftermarket iron heads, unless they are required by some specific class racing rules.
I do agree that the good years of stock heads can support 300hp.
I dont see me saying they were unported? Too many web wheelers around here, at least thats what the 4x4 guys say. They talk like they know everything but dont have much experience.
We've really blown out the original question posted by src5tt. don't know that we are helping him much with all the iron vs aluminum. If cost is a significant concern (when is it not?) then a good set of iron heads will be a benefit. A set of aftermarket heads like World Products (danny clemens comment) should also work for what src5tt is after.
Thanks for all the comments everyone. This definitely gives me a lot to think about. Has anyone here bolted up the GT40P heads? I can get a set of these for approx $500 versus the grand that the edlebrock heads are going to run me. Any thoughts? I'll also be sure to check out the Wold performance heads. Thanks for that suggestion!
Pay attention to your compression ratio. Aftermarket heads are aimed at 302-up engines. If you put 58cc-60cc heads on your 289-292, you will lose compression compared to what you have now and won't see as much hp gain as you may hope. If you want to keep the $$ under control, you can swap in a 302 rotating assembly pretty cheap. Then you can shave aftermarket heads to 54cc and have good compression. I'm not compfortable taking a 58cc head lower than that, but that's me.