aluminum D vs. round port heads
 

I see a lot of posts from guys running aluminum D-port heads. I get the reasoning behind this if a guy already has iron D ports and wants to use his existing headers with a nice upgrade to aluminum heads.

Here is my question - if you don't have D port headers already and they make a round port header for your chassis ... why not just go with aftermarket round port heads? Other than header availability, do aftermarket D port heads have any advantage at all over aftermarket round port heads?

I recently had to deal with this exact dilemma on a personal car. Had already bought round port E-heads for my Catalina. But the log jam was the damn exhaust manifolds. Especially with a street Pontiac, with the great manifolds they had, why deal with the continuous aggravation of tube headers on the street? The endless exhaust leaks at the flanges, rusting out every 3 years, maybe 6 years if coated, extra noise, heat, fitment issues, poor ground clearance and so forth. But the problem is, the round port exhaust manifolds are made of unobtanium. After waiting nearly 2 years I finally gave up, sold the heads and bought a set of D-port Edelbrock heads instead. They do not flow as well, especially over .300 lift, but at least ram air and long branch manifolds are available. D-port heads are more difficult to improve the exhaust port, and probably cost me 20-25 HP. But at least I can drive my car.

If I was going to run tube headers, I would certainly use round port heads.

Another part to this that seems to not be considered is if the lesser port volumes ( area ) of the D port heads work better for your particular cid and the way it’s Cam’ed and geared.

Unless the motor is set up for full race and it’s narrow rpm band then it’s the average Tq and HP numbers that matter most .

i have edelbrock d ports and edelbrock round ports. although i think d port header avail is better still you can get round port headers for alot of cars now. i kinda bastard child my edelbrock dports just because i never liked trying to install 64/7 gto headers on d port heads. for whatever reason, i can install round port headers awhole lot easier. its hard to believe that 330cfm can be got out of the dports but butler has a program for it same as round ports, although round ports can go further,

At the very least, I like the wider bolt spacing on the center ports on round ports.

And, how many pontiac factory round port engines run worse than the d port counterpart? Even the RA2 with it`s d port type intake port is one of pontiac`s best runners.

I know we are talking aftermarket heads, but...

I was starting from a bare block and never considered D ports. My rounds perform great in my street car and it runs like a raped ape…finally.

D ports allow you to run the stock stove choke

Are there any downsides to running round ports on the street? Assume headers and a street/strip engine of 400-462 CID. 290 CFM intake port and HR cam in the 231-245 range on pump gas.

What's the decision tree when going from 260CFM iron heads, to either KRE/Edelbrock D-ports or Edelbrock/SM round ports? At what HP or RPM or application, does the D-port exhaust become a limiting factor?

D-ports will never make power of a round port. My headers are coated and are 28 years old, never rusted. The flanges are separated never any header leaks. D-ports are ok, if you want to use stock manifolds for a nice street cruiser.

I prefer the round ports but there are a few things that might dictate a Dport in certain situations as already mentioned.

Headers are not a big deal to me so that's not even factored in the decision making. Round ports are certainly much easier in that regard anyway and I've run headers for decades on many cars, including daily drivers without a single issue using them.

The choice would really just depend on what I'm trying to do with the car.

Just seems like people doing new builds are always going with the D ports and I don't really understand why! I have 87 cc round port edelbrocks with the old chamber style in a 505 with old faithful and a performer RPM, I can't imagine anyone driving my car and thinking, "ya know, this thing just needs smaller intake ports so it has more low-end" ...

My guess is probably cost being the biggest player lol

And that whole "more low end" myth is funny, amazes me that still floats around the internet but whatayado.

I mean hey, if I had some really nice headers and was upgrading from iron d-ports to aluminum heads, I don't see spending the extra cost for new headers if you are talking about a 550 hp build, something you can drink and drive daily.

But if you don't have headers already and new round port heads cost about the same as new d port heads ....

the cost cant be it, the d ports are more money, i think a few hundred more than even the cnc round ports.

i only bought d ports because my kids car was already running with 6x4s and we was gonna upgrade what he had. but i will say the edelbrock dport is a nice looking head much nicer than my 72cc old style heads i originally bought

Factory iron D ports can be ported to go 290 intake cfm at less then 190 CCs , so why is it so hard to believe that aftermarket aluminum D ports can go 330 when they start off at atleast 188 CCs if not 200?

i thought 260 270 was kinda reaching the limits of an iron d port.

Like has been mentioned. Most Pontiac heads came in D-port. It's what we all were use too. Folks would always have had d-port manifolds or headers. Having said that, A lot of folks would have just upgraded to D-Port Aluminum heads if available. There's a reason Kaufman came out with a D-port aluminum Head. and now Edelbrock came out with a D-Port head. You can build a nice 600 h/P street engine with d-ports.

From what I've seen CNC Dports from Kauffman to go about 325 cfm are about $3200. CNC eddy round ports from Butler at the same 325 cfm are $3700.

So yeah there is a price difference but that's not where the extra costs stop. There are exhaust differences to consider and when people already have a dport car with d port manifolds they are reluctant to spend the extra money for the change. Now you're looking at RA manifolds or headers that have to be swapped and that doesn't always line up with your existing exhaust system either so there are some cost modifications there to consider.

Steve C asked me to post this as he is currently unable.

here ya go, compliments of Steve........

https://www.motortrend.com/how-to/in...head-edelbrock