Author Topic: What is the difference between Round Port and D Port?  (Read 414 times)

Maxthe222

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What is the difference between Round Port and D Port?
« on: October 21, 2019, 06:53:20 PM »
Ok, probably a dumb question this far into building a motor, I know, but now that the motor is coming together i'm being asked a lot of questions and being told what thing do I want where and which exhaust headers am I going to use etc...

So it's the '79 400 W72 XX block, is this a D-port or a round port? Which port do I want? Is one better than the other? Are they interchangeable?
Do I want headers or manifolds that are d-ports or round ports?

Thanxxx
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #1 on: October 21, 2019, 08:06:19 PM »
The 400 W72 engines came with 6x-4 heads. These are D-port heads. The 2 center exhaust ports of these heads are in the shape of 2 capital D's back-to-back. 

The 2 center exhaust ports of round port heads, are slightly separated, and their shape is almost a perfect circle. Here is a link to some pics of D-port vs round port heads.

https://www.google.com/search?sa=N&rlz=1CAHKDC_enUS777US777&sxsrf=ACYBGNRiiq4ovo1S_x4HXzvCR3A4Kdhm6w:1571710586587&q=pontiac+round+port+vs+d+port+heads&tbm=isch&source=univ&ved=2ahUKEwjR18-Z5q7lAhUpnq0KHVe0BnE4ChCwBHoECAkQAQ&biw=1366&bih=609#imgrc=iC3QDabP_EwDoM:

Factory round port heads are rare & now very expensive. You can buy new alum round port heads cheaper than a nice set of factory iron round ports.

Obviously, D-port headers & exhaust manifolds will not work on round port heads.

« Last Edit: October 21, 2019, 08:25:18 PM by oldskool »

Jack

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Re: What is the difference between Round Port and D Port?
« Reply #2 on: October 21, 2019, 10:24:58 PM »
Good question, but I don't think you got an answer as far as which is better. I did not think there was a differance between the 2 other than round is rare and therefore very expensive.




Regards, Jack

nas t eh

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Re: What is the difference between Round Port and D Port?
« Reply #3 on: October 22, 2019, 12:02:41 AM »
The list of Pontiac motors with round port heads is short,
1. 1968 400 RAII
2. 1969-70 400 RAIV
3. 1971-72 455 HO
4. 1973-74 455 SD
5. All the variants of the RAV

The round port heads of the first 4 on this list have larger (taller) intake and bigger better shaped exhaust ports with much higher flow characteristics. All also have the bigger 1.77” exhaust valves.

The V are different again with even bigger separate ports with the valves relocated in an IEIEIEIE arrangement instead of EIIEEIIE

If you are thinking of buying new aluminum heads even the D-ports flow very well out of the box and if bought set up from one of the big Pontiac shops can be CNC ported for only a little more to flow extremely well for street use. Round port aluminum heads have even more flow and more ported potential.
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yellow1098

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Re: What is the difference between Round Port and D Port?
« Reply #4 on: October 22, 2019, 12:13:22 AM »
So the simple answer would be the factory and aftermarket rounds heads flow better and make more power? Right?

Re: What is the difference between Round Port and D Port?
« Reply #4 on: October 22, 2019, 12:13:22 AM »

Maxthe222

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Re: What is the difference between Round Port and D Port?
« Reply #5 on: October 22, 2019, 12:54:49 AM »
I have the 6x4 heads and plan on keeping them, could never afford new aluminum heads. Can the 6x4 heads be opened up a bit more?
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

jonathonar89

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Re: What is the difference between Round Port and D Port?
« Reply #6 on: October 22, 2019, 06:16:44 AM »
I have the 6x4 heads and plan on keeping them, could never afford new aluminum heads. Can the 6x4 heads be opened up a bit more?

D-port heads do very well.  Yes, they can be ported and rival non-ported aluminum heads when properly prepared.

firebirdparts

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Re: What is the difference between Round Port and D Port?
« Reply #7 on: October 22, 2019, 06:59:41 AM »
The Pontiac round port heads (listed above) were designed for high rpm applications from scratch.  The round port itself is not the key to that, but they do all have that visible feature in common.
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b_hill_86

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Re: What is the difference between Round Port and D Port?
« Reply #8 on: October 22, 2019, 07:10:03 AM »
I have the 6x4 heads and plan on keeping them, could never afford new aluminum heads. Can the 6x4 heads be opened up a bit more?

Being in Australia vs US may play a factor along with the current condition of your 6x-4s bit for what it’s worth when I had my heads rebuilt, port matched, a few other small performance minded tweaks the cost ended up not much less than aluminum heads. By the time I was all in it was too late for me to back out and buy aluminum.
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oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #9 on: October 22, 2019, 08:15:05 AM »
"...The Pontiac round port heads (listed above) were designed for high rpm applications from scratch..."


I'll make a comment about this statement.

The RA2 & RA4 engines were designed for more power, above 5000 rpm, since they had the 041 cam.

BUT, I wouldn't call the '71-'72 455HO engines "high rpm", at all. They had the longer 4.21 stroke, but still had cast rods. Most say the safe limit for that combo is 5500 rpm. Not exactly high rpm.

455HO engines came with the 068 cam. In a 455, power probably begins to fall off, slightly before 5000 rpm. That don't mean they won't turn 5500, just that peak hp is well below 5500. Again, not exactly "high rpm". The 068 was not nearly enuff cam for a 455HO. Now, if you swap in forged rods & pistons, along with an 041 cam, you'd have a REAL nice engine. Too bad Pontiac didn't do that. They did a better job with the SD455. Had nice forged rods, & planned to use an 041 spec cam. Did lots of testing with that cam. But, at the last minute, they backed out & went with 744 cam specs instead. Really reduced power, over 5000 rpm. 

So, with 455 or more cubes, forged rods & pistons, and the right cam, you could make lots of power with 455HO & SD455 heads. But, they are just too expensive, especially the SD heads.

Low budget guys are limited to lower priced iron D-ports. 


nas t eh

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Re: What is the difference between Round Port and D Port?
« Reply #10 on: October 22, 2019, 10:48:06 AM »
I have the 6x4 heads and plan on keeping them, could never afford new aluminum heads. Can the 6x4 heads be opened up a bit more?

Being in Australia vs US may play a factor along with the current condition of your 6x-4s bit for what it’s worth when I had my heads rebuilt, port matched, a few other small performance minded tweaks the cost ended up not much less than aluminum heads. By the time I was all in it was too late for me to back out and buy aluminum.

This is becoming more true as the aluminum head price falls and labor to rebuild and port iron heads increases.
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oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #11 on: October 22, 2019, 11:24:18 AM »
"This is becoming more true as the aluminum head price falls..."

Other than the Speedmaster heads, which alum head prices have fallen ?

The price of Edelbrock & KRE alum Pontiac heads have increased in recent years, rather than decrease. Hasn't been that long ago when alum heads were right around $2k. Now the KRE's are closer to $2500, with bolts & shipping. And the Edelbrocks are closer to $3k than $2500.

http://www.krepower.com/Pontiac%20Aluminum%20D-port%20Cylinder%20Heads.htm

https://www.summitracing.com/parts/edl-61599?seid=srese1&gclid=Cj0KCQjw0brtBRDOARIsANMDykaRsHWGqMuFpZOCrOxCdCZFaKkplMqmgxNxuiXZdv72dgXpJIbSFsEaArjAEALw_wcB
« Last Edit: October 22, 2019, 11:35:03 AM by oldskool »

jonathonar89

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Re: What is the difference between Round Port and D Port?
« Reply #12 on: October 22, 2019, 12:10:30 PM »
"This is becoming more true as the aluminum head price falls..."

Other than the Speedmaster heads, which alum head prices have fallen ?

The price of Edelbrock & KRE alum Pontiac heads have increased in recent years, rather than decrease. Hasn't been that long ago when alum heads were right around $2k. Now the KRE's are closer to $2500, with bolts & shipping. And the Edelbrocks are closer to $3k than $2500.

http://www.krepower.com/Pontiac%20Aluminum%20D-port%20Cylinder%20Heads.htm

https://www.summitracing.com/parts/edl-61599?seid=srese1&gclid=Cj0KCQjw0brtBRDOARIsANMDykaRsHWGqMuFpZOCrOxCdCZFaKkplMqmgxNxuiXZdv72dgXpJIbSFsEaArjAEALw_wcB

X2

On top this, if you actually want good aluminum heads, you buy them bare and get them prepared properly.

This is why I just want to get my iron heads done.  Would rather have a professional work them over and do everything right.


yellow1098

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Re: What is the difference between Round Port and D Port?
« Reply #14 on: October 22, 2019, 11:44:20 PM »
I have definitely trying to decide between the KRE and some butler setup eddys for quite a while now...they round option Iv been looking at was closer to 3,500.....have been actually surprised tho are the only two options unless you wanna spend 5-6k

Re: What is the difference between Round Port and D Port?
« Reply #14 on: October 22, 2019, 11:44:20 PM »



Maxthe222

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Re: What is the difference between Round Port and D Port?
« Reply #15 on: October 23, 2019, 03:40:21 AM »
If I have the pontiac 6x4 heads well machined, how much will I be missing out on if I don't get those repro heads?
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

jonathonar89

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Re: What is the difference between Round Port and D Port?
« Reply #16 on: October 23, 2019, 08:42:47 AM »
"...This is why I just want to get my iron heads done.  Would rather have a professional work them over and do everything right."


You are only about 55 miles from Paul Knippen.

https://www.google.com/search?rlz=1CAHKDC_enUS777US777&sxsrf=ACYBGNRGYd2jNmZhIh_3Zq6a4O8-hlQ7Tw%3A1571774326829&ei=dl-vXaSUMtGAtgXnupvwDQ&q=barrington+il+to+sandwich+il&oq=barrington+il+to+sandwich+il&gs_l=psy-ab.12..33i22i29i30.21293.31449..33999...0.2..0.328.3189.0j13j4j1......0....1..gws-wiz.......0i71j0i67j0i22i30j0j33i299.qyN_rmOpgDA&ved=0ahUKEwikp6vT07DlAhVRgK0KHWfdBt4Q4dUDCAs

https://www.facebook.com/PaulKnippensMuscleMotors/

He actually does nice work from what I see online.  I’m probably going with Paul on redoing my 6X-4 heads.  I tried calling SD not too long ago but no answer.  I’ve always heard they’re busy.

pancho400cid

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Re: What is the difference between Round Port and D Port?
« Reply #17 on: October 23, 2019, 10:53:13 AM »
Interesting discussion.  A pic is worth a lot so I'll put this up as I had it (not my pic... got it off the web).....  Round port head on top.  D port head on bottom.


« Last Edit: October 23, 2019, 10:55:07 AM by pancho400cid »
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oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #18 on: October 23, 2019, 10:55:31 AM »
If I have the pontiac 6x4 heads well machined, how much will I be missing out on if I don't get those repro heads?

I'm not real sure about your question. But, SOME aluminum heads offer more POTENTIAL power gains.

Higher flowing heads will increase power mostly above 5000 rpm, where most street cars don't operate, most of the time. For street use, I'd prefer more power/torque in the low to mid rpm range, where street cars spend most of there time.
« Last Edit: October 23, 2019, 11:00:22 AM by oldskool »

nas t eh

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Re: What is the difference between Round Port and D Port?
« Reply #19 on: October 23, 2019, 11:49:04 AM »
"This is becoming more true as the aluminum head price falls..."

Other than the Speedmaster heads, which alum head prices have fallen ?

The price of Edelbrock & KRE alum Pontiac heads have increased in recent years, rather than decrease. Hasn't been that long ago when alum heads were right around $2k. Now the KRE's are closer to $2500, with bolts & shipping. And the Edelbrocks are closer to $3k than $2500.

http://www.krepower.com/Pontiac%20Aluminum%20D-port%20Cylinder%20Heads.htm

https://www.summitracing.com/parts/edl-61599?seid=srese1&gclid=Cj0KCQjw0brtBRDOARIsANMDykaRsHWGqMuFpZOCrOxCdCZFaKkplMqmgxNxuiXZdv72dgXpJIbSFsEaArjAEALw_wcB

X2

On top this, if you actually want good aluminum heads, you buy them bare and get them prepared properly.

This is why I just want to get my iron heads done.  Would rather have a professional work them over and do everything right.

Yes the Speedmaster heads or for $3000 you can get fully prepped and ported Edelbrocks from SD, I don't think he has raised his prices in quite a while.

http://www.sdperformance.com/viewProduct.php?productID=37

Maybe an iron D-port can be worked to this kind of performance but it will be similar money, so why would you do it?
« Last Edit: October 23, 2019, 12:13:05 PM by nas t eh »
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Maxthe222

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Re: What is the difference between Round Port and D Port?
« Reply #20 on: October 23, 2019, 03:09:15 PM »
Quote from: nas t eh
Maybe an iron D-port can be worked to this kind of performance but it will be similar money, so why would you do it?

And that does basically answer my question, to rephrase it better, how much better performance can be gianed through using aluminum new heads over properly doing the old ones.

Easy, originality. Also, the Australian dollar is terrible right now. I have the two 6x4 heads the motor came with here and now. Buying and freighting new aluminum heads cannot possibly be cheaper than just having the ones here done up nice. Although I'd love to rev the guts out of this thing till it blows, I don't know how often I'd have the car doing more than 5000rpm
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #21 on: October 23, 2019, 08:28:58 PM »
For under 5000 rpm operation, no porting is needed. for the 6X heads.

In the states, a good head job, with stainless valves, new guides, seals, 7/16 studs, and a nice 3-angle valve job, will usually cost $1000 or less. My neighbor recently had a set of #62 heads done. Cost him about $800.

And, this probably makes some guys mad. You don't even really need 2.11 intake valves to make decent power. Brad Koivisto runs low 11's in his Stock legal '74 GTO, with #46 heads. It has low CR, and small valves. Bill Rink runs mid 10's with his Super Stock '74 GTO, also running small valve #46 heads. Adam Strang runs mid 10's with his '68 Bird Stocker, running the small valve #18 heads.
« Last Edit: October 23, 2019, 08:40:52 PM by oldskool »

yellow1098

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Re: What is the difference between Round Port and D Port?
« Reply #22 on: October 23, 2019, 09:00:41 PM »
Anybody know any good ones for sale maybe used? Haha.... for my 461 bottom end?

Maxthe222

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Re: What is the difference between Round Port and D Port?
« Reply #23 on: October 24, 2019, 04:09:10 AM »
So if i'm rebuilding my stock heads, what do I need to put on them? All I have a complete original engine. I take it I can't use the original valves and springs etc?
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

oldskool

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Re: What is the difference between Round Port and D Port?
« Reply #24 on: October 24, 2019, 07:08:08 AM »
So if i'm rebuilding my stock heads, what do I need to put on them? All I have a complete original engine. I take it I can't use the original valves and springs etc?

You CAN use stock valves. Many do. BUT, if they are original, they are quite old & have gone thru lots of heat cycles. They are a 2-piece construction. The hardened tips are welded on. Lots of these valves have failed, which will take out a piston, at the very least.

Therefore, many opt for new one piece stainless valves. Ferrea 5000 series is the most popular SS valve. SI also has some decent valves. Stock length for 6X heads is just under 5". If you plan to run a high lift cam, you can go with longer valves. 

https://butlerperformance.com/i-24453180-ferrea-high-performance-stainless-steel-intake-valve-setfer-f5082-8.html?ref=category:1400522

https://www.ebay.com/itm/Ferrea-Intake-Valves-HDia-2-11-For-60-12-PONTIAC-400-428-455-11-32-4-98-F5082/273023602417?epid=1172509186&hash=item3f91798ef1:g:kNgAAOSw301aWgq9

Many prefer to go with 1.77 exhaust valves. But, they are not needed. And, using 1.77 valves in 1.66 seats will require that the seats be machined bigger. This will remove most of the factory hardened seat material. I'd just go with 1.66 valves.

https://butlerperformance.com/i-24453162-ferrea-high-performance-stainless-steel-exhaust-valve-setfer-f5080-8.html?ref=category:1400522

I think the part number for the SI brand short 1.66 exhaust valve is 6001SG. The short 2.11 valve is listed as an SD455 intake valve. You can order these directly from SI. Don't know the price. A well known Pontiac engine builder uses & recommends these valves.

http://sivalves.com/flipbook/2016-SI-Catalog.html#p=43

http://www.sivalves.com/

Original springs are also very old & most are very used. I'd go with new springs, suitable for the cam you'll be running.

Unless you're going with a roller cam, or a HFT cam with more than about .470 lift, some CC 988-16 springs will work.

https://www.ebay.com/p/192751619?iid=163894889355&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=163894889355&targetid=541454196652&device=c&mktype=pla&googleloc=9025470&poi=&campaignid=6470549460&mkgroupid=81274343007&rlsatarget=pla-541454196652&abcId=1139336&merchantid=101503623&gclid=Cj0KCQjwl8XtBRDAARIsAKfwtxDllrkHdHmITEfoOzjbBMuZF22AKKVn68Kt1RmBqDN0bCqCRuTyPsIaAoV3EALw_wcB

Here's some cheaper, slightly weaker springs from a Pontiac engine builder. He says these are good for cams as big as a "high lift 068", which would be include a Summit 2801. They're for stock length valves, with an installed height of aprox 1.6". Longer valves will require different springs.

https://www.ebay.com/itm/Pontiac-V8-stock-valve-springs-400-455-389-350-428-GTO-Firebird/283643140543?epid=672937061&hash=item420a72d9bf:g:LYAAAOSwmrlU0mJ9

You CAN use your bottleneck rocker arm studs. BUT, it's better to buy 7/16 BBC type studs. If you go with stock length valves, 1 3/4" factory BBC studs will work. If you have any friends who are long time BBC guys, they'll probably have a set of original BBC studs you can buy cheap. But, there are new ones that cost less than $40.

https://www.jegs.com/i/JEGS/555/20582/10002/-1

https://www.amazon.com/Elgin-2-560-Screw-Rocker-Bottom/dp/B01MZEDEFI

https://www.summitracing.com/parts/mil-84287

You'll need new valve guides. The machine shop will probably have a particular brand/type they prefer.

Most new SS one piece valves don't have a groove for the factory type rubber O-ring seals. So, the shop will need to machine for & install some good positive valve seals.

Just a note here: There are some Chevy shops that have very little to no experience rebuilding Pontiac heads. Best to find a shop that HAS had lots of Pontiac head experience. 

« Last Edit: October 24, 2019, 08:51:08 AM by oldskool »

Maxthe222

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Re: What is the difference between Round Port and D Port?
« Reply #25 on: October 25, 2019, 02:53:04 AM »
Oh boy, that's a lot to go thru.
All good info I can pass onto the machine shop, I know how experinced you are with getting 400's to go fast, so I can say it's "tested" and "referenced"
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula 400 4-Speed

Re: What is the difference between Round Port and D Port?
« Reply #25 on: October 25, 2019, 02:53:04 AM »
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