which ones flow better after port/polishing?

For the Vortechs, I'm refering specifically to the Pro Action ones

 

Its Vortec not Vortech. But i would say the Fastburns because they have a 40cc bigger runner. 170cc for Vortec vs 210cc for fastburns. But its not all about flow, more important is flow velocity.

 

ok, so how do you know which is better?

 

The fastburns are overpriced and are not good for the street, because they have 210cc runners.

 

In *ultimate ported form* I'd lay bets on the cast iron vortecs.
Especially on a 350 cu in based motor.
equal valves sizes though.

Why?
1. its cast iron = more power than alumium.

2. You can achieve the *advertized (prototype) flow* of the fastburns
+/- 270cfm @ 28" with the smaller sub-200cc finished ported vortec head once fully ported with big valves. ( 170cc stock)

This much flow on a head with less port volume on a 350 based motor is going to have a better more powerfull torque curve and high horespower than a large 210+ cc ported fastburn
even if the fastburn end up with more flow.
The smaller port will be better.

On a larger 400+cu in motor as a base, it may be different
and better favour a ported larg(er) ported fastburn head.

Assuming equal *street able* compression ratio , valve size CID and practical operating RPM range.

Hard to beat the $price$ too.

 

I though aluminum made more horsepower than cast iron, because you could run higher compression and were lighter??

 

I thought that aluminum was better because it was lighter but cast is better because it can take more punishment. I thought cast heads could support higher compression.

 

1. lighter doesn't = more horsepower, the weight has no effect.
But "lighter" goes require less power to accelerate.
Top speed is almost not really affected by the weight.
Mechanical friction and air resistance is much more of a factor.

2. A cast iron head will out-power a alumium head of equal
design. It is more thermally efficient. * especially if you're limited to streetable compression ratios.*
A alumium head typically need about a 1/2 ratio more compression just to equal the power and thermal efficientcy of cast iron. Fortunatly it is also a little more tolerant of the higher compression ratio required. This has beed demonstrated on engines and in the winner's circle many times.
We won't even get into durability......

Here is another consideration:
If, you have a $limited budget$, keep in mind you can buy a great cast iron head for the same or less $$$'s than a good or
so-so alumium
head. You'll go faster and for less.

 

But if the cast iron head make more power, why would the aluminum heads be more expensive? Wouldn't people want the cast iron heads?

 

Because aluminum costs more!!

 

What people want and what material makes more power is two different things. One is based on physics and reality, the other on
an uninformed market choice.

Cast iron is cheaper than cast alumium.
Casting cast iron into heads is cheaper than casting alumium into heads.

Bang for the buck, durability and ultimate power = cast iron

Light weight and repairability = aluminum

 

Ok, so for a street engine, specifically built for max power on 87 octane, iron Vortec heads would be the best choice, got it.

Thanks (even though I lost track of the thread among the multitude of threads I started in a short time period)