What are the advantages and disadvantages to using these materials when making selections for cylinder heads. They are for my 351w, its a 1979 block. I am wanting to get just shy of 375hp out of it. So I am interested in what I need to take into account to achieve that number. Granted, camshafts, lifters, valves, connecting rods, and crankshafts will also play a vital role, but we will cross that bridge when we get there. Thanks.

 

Here is my understanding. You are going to get a lot of urban myth on this, but...

Cast Iron Heads
Heavy
Typically not very high performance and thus do not flow very well (although some performance guys make good iron heads)
Typically require machining to flow well
Will crack when very hot

Aluminum
Light
Very prevalent in the aftermarket performance arena
Typically flow well because they are designed for performance
Warp when hot which can force you to machine them if you have a problem

Good 351 heads to look into depending on what you are wanting to do in no particular order:
AFR
Twisted Wedge
CHI
Dart
Brodix
Candfield
Edelbrock RPM XT (Best flow in their class but limited to 351CID)
Yates (If you are really serious)

Regardless of what you buy, think lash caps. I had a terrible experience with my valve stems getting trashed after a few thousand miles.

 

cowboy already mentioned the most. but you'll save about 50lbs with alum heads under your hood. huge difference again if you have them shipped

 

True Kalli...Also huge if you are trying to get weight distribution close to 50/50 and also huge if you are racing and need to make up for the extra cheeseburger you ate!

 

The reason cast iron heads generally don't flow as well is due to the limits of the casting process. There are just some things you can't do with castings. And CNC work on cast iron is comparatively expensive, cast iron being much harder than aluminum, so it costs more to make a finished product in cast iron. And at the end of the day, you still have a heavy chunk of iron sitting on top of your engine, which isn't ideal for someone with pure performance in mind.

Cast iron heads are still more durable and in theory they allow for better combustion because the chambers stay hotter, reducing quench, but aluminum heads cool better, flow better (generally), and are much lighter, so they're much more beneficial to the performance crowd.

 

All of the above ...PLUS they look a HE!! of a lot cooler.

 

If you only want 375 out of a 351w, I'd keep the stockers, do a decent cam, intake and carb. Cheap and will put you reliably where you want. If you asked.

 

Something else to keep in mind, because Aluminum heads run cooler, you can get away with running a higher compression ratio and still run on pump gas.

 

you musta had some crap valves or something. ?!?!?!!

 

Yep! They were AFR valves. JUNK! Thats why when somebody talks about getting AFRs I tell them to buy bare castings and then have them built up with better quality parts.

Hey, did you check out my Vid on You Tube that I put up over the weekend?