Question for the head porting experts.

[Cuda416]

I have a question about port shape. Watching Vizard, he mentions the "ideal" port shape can be represented by a long horn/cone shape, I forget which. The problem is we have valves in the way which means we have ports that are "curved" which is not ideal. The question then, is the general goal, when shaping the port, to get it to a theoretical horn/cone by adjusting the CSA throughout the port to change in the same gradual way with respect to the change of CSA along the port path ( not talking about the shape of a CSA slice) of the port?

 

[ch1ll]

No, not only will you likely hit the water jacket, you need to increase flow and efficiency the port has to offer. Watch more of his videos, he explains alot. I have watched the porting videos several times each, even the chevy and ford videos. Each time I have picked up something new. His porting book is a good read.

 

[Cuda416]

No, not only will you likely hit the water jacket, you need to increase flow and efficiency the port has to offer. Watch more of his videos, he explains alot. I have watched the porting videos several times each, even the chevy and ford videos. Each time I have picked up something new. His porting book is a good read.

Oh I'm not talking about it in the literal sense. But there are times when filling port sections with epoxy helps which leads me to the question. I read somewhere years ago, like 30, that a "D" shaped exhaust port was an attempt to do somethign similar. Maintain the shape and make it "seem" like it was straight wrt flow rather than bent.

 

[ch1ll]

Only way to fill a exhaust port is weld it. Your not going to turn passenger car heads into race heads, and you wouldn’t want to. They would like performing badly on the street. That being said, even the worst mopar heads can be ported to flow 200 or more cfm which will support 400 hp or more. Your next biggest challenge is getting your intake manifold to flow as much as your heads. Its all about the combination.

 

[Cuda416]

Only way to fill a exhaust port is weld it. Your not going to turn passenger car heads into race heads, and you wouldn’t want to. They would like performing badly on the street. That being said, even the worst mopar heads can be ported to flow 200 or more cfm which will support 400 hp or more. Your next biggest challenge is getting your intake manifold to flow as much as your heads. Its all about the combination.

Ok, we're going to disagree to disagree.

First of all, I'm not talking about turning passenger car heads into race heads, I'm talking theory.
Second, there are people on this board who easily get small block heads to over 260 CFM so I'm not sure where the 200cfm number comes from especially since stock magnums are 210-220 out of the box.

Thanks for you're contribution.

 

[ch1ll]

Ok, we're going to disagree to disagree.

First of all, I'm not talking about turning passenger car heads into race heads, I'm talking theory.
Second, there are people on this board who easily get small block heads to over 260 CFM so I'm not sure where the 200cfm number comes from especially since stock magnums are 210-220 out of the box.

Thanks for you're contribution.

I said 200 or more out of the worst heads. I have seen top professional porters get 246 intake out of 302 castings which do not lend themselves to porting. It depends on your skill level and experience porting.

 

[Cuda416]

So back to the original question which had to do with port shape and general goals.

If someone (a head porter) can address that I'd really appreciate it.

 

[Hysteric]

I have seen top professional porters get 246 intake out of 302 castings which do not lend themselves to porting.

I've managed to get mine into the 240's with an 11/32 valve. If you minimize the obstruction at and around the the valve stem you can get good flow out of them.

 

[abdywgn]

something like a tunnel port, shaped like a traffic cone?

 

[Killer6]

So back to the original question which had to do with port shape and general goals.

If someone (a head porter) can address that I'd really appreciate it.

Look, You're asking very general questions. Air follows the same laws every time, but not every port applies those laws the same, bad ports don't respond to the same moves as good ones. So the general answer is, yes tapering a port is desireable as long as the big end isn't too big, & small end too small...but that needs to stop & transition at or before the bowl or pocket.
The higher & straighter a port is, the less CA & valve dia. it needs to flow the same air, and will do it at a higher velocity which = more tq & hp for a given flow. Just simply going by a "reducing CA as it goes" is a fallacy if a port sucks in shape, form, & bias.
All the work that gets done is to make sucky ports ( and that's a lot of them), suck less, so that the "ideals" can be applied as much as possible. A bad port likes bigger valves and CA, but that doesn't mean the intake runners need to be, since the port sucks it needs all the "pocket storage" it can get.
"Generally" that's about it.

 

[Cuda416]

Look, You're asking very general questions. Air follows the same laws every time, but not every port applies those laws the same, bad ports don't respond to the same moves as good ones. So the general answer is, yes tapering a port is desireable as long as the big end isn't too big, & small end too small...but that needs to stop & transition at or before the bowl or pocket.
The higher & straighter a port is, the less CA & valve dia. it needs to flow the same air, and will do it at a higher velocity which = more tq & hp for a given flow. Just simply going by a "reducing CA as it goes" is a fallacy if a port sucks in shape, form, & bias.
All the work that gets done is to make sucky ports ( and that's a lot of them), suck less, so that the "ideals" can be applied as much as possible. A bad port likes bigger valves and CA, but that doesn't mean the intake runners need to be, since the port sucks it needs all the "pocket storage" it can get.
"Generally" that's about it.

Yes it's a very general question as it's meant to be. I am trying to get a handle on the basic theory of things before getting into specifics. Your answer helps so thank you for that.

I understand the CSA from valve to gasket is going to change and the specific delta is important but different in all cases.

My question is maybe better stated in asking specifically should the delta/taper "cone" shaped or "trumpet" shaped if that makes sense

 

[92b]

Yes it's a very general question as it's meant to be. I am trying to get a handle on the basic theory of things before getting into specifics. Your answer helps so thank you for that.

I understand the CSA from valve to gasket is going to change and the specific delta is important but different in all cases.

My question is maybe better stated in asking specifically should the delta/taper "cone" shaped or "trumpet" shaped if that makes sense

I think the trumpet shape your referring to is for the first piece in the system on the end that sees the air first. The entrance. Like a velocity stack on fuel injection. The bell on the end is to provide a radiused inlet as opposed to a sharp edge inlet which creates turbulence. Air likes the radius better. This is why a radiused inlet or clay in the same radiused shape is put at the inlet end of the port on a head that is being flowed on a flowbench. If the intake manifold is attached then obviously the radiused inlet is not needed at the head port inlet.