A couple of you mentioned cross sectional area and I think that is a much better way to compare the port volume of these heads. I read an article in car craft recently about some new heads from Jegs for the Ford Windsor 302-351. The valves are angled for less valve shrouding and the way the head is designed the intake port is like 245cc. The article mentioned how this may sound huge on a small block, but that the way the port is designed accounts for the extra volume and it is far from a hogged out port. The cross sect. width was like 2.7 on the new Jegs heads and 2.55 or so on 170cc windsor heads.The way the valve is positioned has a lot to do with the power and velocity of the air. Air has to make sharper turns on a 23 deg. head compared an 18. I'm sure the same applies here, and I bet these heads make power lower in the rpm band then you guys are saying. I'm sure they are capable of 7K, but 6500 with the right cam and we're talking serious power.

 

The 18* valve slant gives the air, as it enters cylinder, past the chamber wall, an advantage, but it's not an advantage, as the air approaches the intake valve.

Actually, size contributes also. The port, at the flange, is I believe, 2.88 X 1.06.

 

You have to keep in mind that when you discuss port volumes it's not just the numbers that mean everything. The port is angled higher than a 23* head therefore the volume is more in port LENGTH than in CROSS-SECTION. Larger cross-section has more adverse side-effects on your drivability and power curve than length does.

Plus with the higher ports you get a better port trajectory towards the valve and better line of sight with the injectors. And ram tuning effects will be more effecient since a lot of the intake charge's energy will be spent hitting the valve and entering the cylinder rather than being wasted while colliding with the port walls. And as far as i know, with the higher, more symetrical port the air stream is more uniform with less turbulance so the incoming air retains much more of it's energy while traveling though the port. After learning all this over the years, these are the reasons why i want to get the higher angled heads over the 23* stuff. You might spend more money up front, but people need to realize that in the end you'll get more bang for your $$$.

On the intakes, the brodix 1800 and 1801s are readily available. KT used an 1801 and had it worked on by [some company, i forget right now] and it fit rather well in the engine compartment. He suggested the 1800 if you want to try to fit it under the stock hood as it is shorter than and has less plenum volume than the 1801.

 

Ya but to fully take advantage of them you need some big headers. Why buy the 18x if you are already going through with the expensive conversion/casting price? why not go with some better heads? You are going to use a hyd roller with these big heads? no.

*shrug* just my opinion

 

On it's won merits, I agree. But on an 18* head, (for the intake) does it really? The alteration of the valve angle by 5*, is tipped in the direction adverse to the port. This is why it becomes necessary to raise the port, at the flange, with a steeper angle to the valve, just to regain some of what was lost, with the 5* valve slant. When one views the 'ideal' port to valve relationship, as the valve axis in line, with the port axis, which AFAIC, is not achieveable, it becomes easier, to understand. The 18* valve angle, does improve the flow entering the cylinder though, which is very important.