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Old 10-06-2010, 04:24 PM
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After market Pontiac D port heads?

Title say it all, does any one make after market Pontiac D port heads? Looking for something that has higher flow numbers than stock D port.

BT

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Old 10-06-2010, 04:31 PM
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Mr. Creech should be along in a little while to shine the light of truth on head selection.
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Old 10-06-2010, 05:40 PM
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I hope so...

I kinda enjoy reading his stuff.

Now if I could only get motivated to do something with that 400 bolted to the stand in my garage.
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Old 10-06-2010, 06:23 PM
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Practically all of the aftermarket heads made for Pontiac engines have D-port exhausts. The Edelbrock heads have D-port widely spaced (RA IV-type) exhaust ports.

The OM round port heads were made as a convenience by the factory for the racers using Pontiac engines, not necessarily for a flow advantage, because the close spacing of the traditional D-port heads caused header fitment problems w/ported heads. After the redesign and port changes, a flow increase was seen, even though that wasn't the sole intention.

EDIT- It's worth mentioning there are raised intake port aftermarket heads available, for those wanting to run large CFM ports.

There are those who call any RA IV-type flanged Pontiac head- even if the ports are "D" shaped, as "Round Port" heads. This is true as far as the type of header flange that has to be used, but the ports themselves are D shaped, in most all cases.

Pont. D-port heads had the flat part of the D at the insides of the center ports. Aftermarket heads tend to have the flat part of the D at the bottom of the port.


Last edited by cobalt327; 10-06-2010 at 06:49 PM.
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Old 10-06-2010, 06:59 PM
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Here's a view of the Edelbrock ports. As can be seen, the exhaust ports (that Edelbrock call "D-Port", have the RA IV flange, and the "D" is turned 90 so the flat is at the bottom of the port instead of the insides of the center ports:



I would have added it to the above post- except the too short time limit for editing bites again.
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Old 10-06-2010, 10:33 PM
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Here's the first, and best, aftermarket D port Pontiac head. http://www.krepower.com/KRE_d-port_heads.htm
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Old 10-06-2010, 11:02 PM
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A roundish port that has to make a turn upsets flow because the port is basically the same diameter all the way through the port. Because the short side radius is.....shorter......the gases do not flow through the port without turbulence. They move quicker around the long side radius and slower around the short turn radius.

A "D"-shaped port is made with the flat part of the D on the port floor, because that's where it needs to be in order to make the port think it is the same diameter all the way along its length. A "D" port tricks the head into thinking that the ports are all the same diameter and straight, thereby minimizing turbulence and aiding flow.

At least that's the way it was explained to me and it makes sense that it works that way.
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Old 10-06-2010, 11:23 PM
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Quote:
Originally Posted by techinspector1
A roundish port that has to make a turn upsets flow because the port is basically the same diameter all the way through the port. Because the short side radius is.....shorter......the gases do not flow through the port without turbulence. They move quicker around the long side radius and slower around the short turn radius.

A "D"-shaped port is made with the flat part of the D on the port floor, because that's where it needs to be in order to make the port think it is the same diameter all the way along its length. A "D" port tricks the head into thinking that the ports are all the same diameter and straight, thereby minimizing turbulence and aiding flow.

At least that's the way it was explained to me and it makes sense that it works that way.
That is correct TI. That's why all of the good aftermarket "round port" heads have a flat floor. Both, my Wenzler Super Chiefs and my Wenzler series II High Ports, that Kauffman did for me, have flat floors and if you ever see a Tiger head, it's the same.

Last edited by WDCreech; 10-06-2010 at 11:37 PM.
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