[bwomp969]

I was wondering if someone could either point me in the correct direction to learn about what everything means with exhaust ports and etc that would help explain whats what about a SBC head?
or maybe someone could just tell me?

Im thinking about cast iron large port vortec heads but to be honest I really dont know why they cost so much compared to normal vortec heads, cast iron of course? and is there a major difference in aluminum vs cast iron?

 

[ap72]

They are not more because they are iron- aluminum costs more. The exhaust port is the hole that the exhaust flows out of past the valve and into the manifold/header. Large intake ports work better on large cubic inch engines or engines that have high valve lift numbers.

Most people want aluminum heads but on an exactly matched comparison iron heads will make a little more power. Aluminum heads are sought after beacuse they are easily machined, easily repaired, and allow higher compression because they dissapate heat faster.

 

[TroyBoy]

Weight is a consideration also.

 

[ap72]

Weight is a consideration also.

By that he means Aluminum is lighter which usually makes your car accelerate faster and handle better.

 

[bwomp969]

you guys are awesome thankyou
now can you inform me about what exactly the rest of the measurements are in a head?
for example:
# 225cc intake port
# 77cc exhaust port
# 65cc combustion chamber
# Improved airflow
# Flows 281 cfm @.600"
# Uses Fel-Pro #1470 exhaust gasket, may require minor trimming.

 

[Deez]

Way. Not too sure if those are the heads you want as you don't list your engine/combo/intended use. They are rather large for most smaller ci 'street' apps and although a nice head probably not what you need. IMHO, you will find better off the shelf performance in something like the RHS Vortec head, they'll support about 500HP.

As for the cost of aluminum vs iron, I find it hard to believe the most abundant metal on the planet is harder to mine, extract and/or process than iron ore. I suppose with it's prevalent use across the globe demand is high enough that this most abundant metal is scarce. NOT.
Aluminum is the most abundant metal to be found in the earth's crust (8.1%).


Oh, and FWIW (rag article)

Iron vs. Aluminum Heads

Can you guess what we learned? Zilcho. As in zero difference anywhere in the power or detonation characteristics of the iron versus aluminum heads. Even the optimum total ignition timing was the same at 36 degrees. Regardless of coolant temp, rate of acceleration, steady state, or through a sweep, the dyno curves for the two styles of heads were identical. If anything, we could squint and guess and mumble that maybe aluminum heads were better by 2-3 hp. But the one thing we could never say is that the iron heads retained more heat and made more power than the aluminum. Maybe it's different on some engines with a drastically different water-jacket design, but we'll stand up and say that the old bench-racing line just ain't true.

 

[bwomp969]

Way. Not too sure if those are the heads you want as you don't list your engine/combo/intended use. They are rather large for most smaller ci 'street' apps and although a nice head probably not what you need. IMHO, you will find better off the shelf performance in something like the RHS Vortec head, they'll support about 500HP.

As for the cost of aluminum vs iron, I find it hard to believe the most abundant metal on the planet is harder to mine, extract and/or process than iron ore. I suppose with it's prevalent use across the globe demand is high enough that this most abundant metal is scarce. NOT.
Aluminum is the most abundant metal to be found in the earth's crust (8.1%).


Oh, and FWIW (rag article)

Well I plan on putting these heads on a machine and rebuild 350 sbc that will be going into a 1983 mazda rx7, i plan on either NASA racing or SCCA racing with the setup
I have many many plans that my budget cant touch but im direly trying to learn about whats what and why certain parts are so expensive and others so cheap
Once again thankyou very much for the vey appreciated information

EDIT: Is there some fully assembled RHS vortec heads that I can possibly buy? I looked up RHS vortec heads and they are bare from RHS. Now thatd be all fine and awesome but I dont have the know how and the cash to build my own rhs vortec heads
any suggestions?
what about this top end kit? http://www.jegs.com/i/GM+Performance/809/12558060K/10002/-1#
any opinions? of course Id need bolts and such

 

[cobalt327]

The cost of aluminum (especially virgin) is due to the high energy requirements for refining it. The raw materials are "dirt" cheap.

 

[SSedan64]

Assembled RHS's
http://www.competitionproducts.com/products.asp?dept=693

 

[ap72]

If you're planning on road racing with 350CI a 190-200cc intake port would probably be a lot better for ya as it would tend to have a broader torque band than a larger CC runner on that small of displaceemnt of engine.

As far as assembled heads- buying assembled can save you a few bucks but if you buy bare you can select the rest fo yourvalvetrain to more appropriately match your engine- expecially important on springs but you can also select your own valves which can affect flow and/or stability. IMO in racing applications its worth buying bare and having all the componenets properly matched to your engine, its less important when you just want to quickly build a hot daily driver.

 

[Jsup]

I was wondering if someone could either point me in the correct direction to learn about what everything means with exhaust ports and etc that would help explain whats what about a SBC head?
or maybe someone could just tell me?

Im thinking about cast iron large port vortec heads but to be honest I really dont know why they cost so much compared to normal vortec heads, cast iron of course? and is there a major difference in aluminum vs cast iron?

Don't sweat exhaust ports. There are 1000 HP motors running 250 CFM on the exhaust side.

There's a whole lot on heads, nothing that can be summed up in three sentences or less.

Aluminum is all about heat. They get rid of the heat better than cast iron allowing for higher compression.

I posted here a long paper I spent weeks developing and researching. I'll see if I can find the link.

on't be fooled by flow numbers. Those who brag about flow typically don't understand what makes a head work.

There's elements like flame travel, fuel suspension, cross sectional areas, etc...

The whole purpose of a head is to suspend fuel and deliver it effectively to the cylinder. The best way I know of to do that is

1. Wet flow, used by all but 2 manufacturers, Nascar, and all other high end engineers

2. Spintron with high speed cameras. Allows engineers to see exactly what is going on while the motor is running in its operational conditions.

Runner design is more important than flow numbers and these techniques help define what that means.

I'll see if I can find my link.

 

[Jsup]

you guys are awesome thankyou
now can you inform me about what exactly the rest of the measurements are in a head?
for example:
# 225cc intake port
# 77cc exhaust port
# 65cc combustion chamber
# Improved airflow
# Flows 281 cfm @.600"
# Uses Fel-Pro #1470 exhaust gasket, may require minor trimming.

# 225cc intake port-volume size of the runner, the path air takes through the head it is a STATIC measurment. Be careful. Some well known manufacturers will list the BEST port flow using clay pipe as opposed to the AVERAGE port flow across the board. There's a lot of tricks to make this number seem more impressive than they are.
# 77cc exhaust port-same as intake, just air going out, not in
# 65cc combustion chamber-will effect your compression. Needs to be done in consideration of your pistons and goals
# Improved airflow-talking dry flow, which is a guideline, means less than port design.
# Flows 281 cfm @.600"- how much air will flow through the sized ports mentioned above
# Uses Fel-Pro #1470 exhaust gasket, may require minor trimming The size of the ports on the intake gasket. Need to match it to your intake.

Hope it helped.

 

[Deez]

A Spintron is not used for observing A/F charge or atomized fuel. The adding of Spintron to this post is ridiculous, it's fodder. The head is used to mount the valve train, cover the cylinder with a combustion chamber and deliver the A/F charge to the cylinder via the intake runners/port as well as mount the intake manifold (or other). You do not need to match ports to gaskets, especially if the gasket is larger than both manifold and head. Enlarging the manifold and head to a gasket is not the way to do it and may actually have detrimental results if the manifold and head are close to begin with. I am not posting to be a smart alek, but this information may lead people to do things that should not be done... IMHO Also, flow numbers do mean something, but not as a stand alone reference. Having a set of heads flowed will give you pertinent information which may be used for other aspects of the build. Flow numbers will give an approximation how much HP the head will support - e.g. a head that will not flow 250cfm is not going to make 600HP without power adders but a head that flows 330cfm will be more apt to make more power if the combo is right. Most head mfrs exhaust ports are closely matched to work with the intake during the design and development of the head. Some heads leave additional material for head porters, so they can shape the port to whatever works best for them, depending.

Is there some fully assembled RHS vortec heads that I can possibly buy? I looked up RHS vortec heads and they are bare from RHS. Now thatd be all fine and awesome but I dont have the know how and the cash to build my own rhs vortec heads

They are available and would likely be a very good head for your app. Those heads may support 500HP no problemo, even with their smallish ports. They may be lacking on the very low end compared to a std set of vortecs but leave them behind as a whole, all the way around.

 

[ap72]

Jsup has good points, he just goes a little overboard, though many people go overboard on other aspects so maybe its needed to keep a balance...

And 250cfm could support a 600hp engine if the rest of the engine was built to make it happen with those heads. Peak flow numbers while an important indicator are not the only indicator. All things need to be considered in their due balance and if it was so easy as summing it up in a few sentences on an internet forum then there would be only one perfect head design and we all would be running it.