Edelbrock Aluminum Heads- D-Port vs. Round Port

There are many questions regarding the types of Edelbrock Aluminum Pontiac Heads. They can be quite confusing. Here at Butler Performance we try and give you the knowledge to distinguish the head types and assist you in selecting the correct head for your application.

The first question is the ability to distinguish between the two types of heads. Below is a picture of the Edelbrock Round Port and D-port heads side by side. One would notice that the round port actually looks like a sideways "D" that is pointing upwards. This is not a "D-Port" head but a round port instead. The d-port head looks like a set of "D"'s mirroring each other, in other words back to back.  The round port heads take a round header flange.


Another question is can I identify the Edelbrock head type just based on casting number?

The answer is normally no. Although you can distinguish the head class or type, you cannot identify if it is bare or complete, nor can you identify chamber sizes. For example, the casting number for a typical Pontiac Edelbrock Round Port style head is 6056. This is the base casting number only which is shared by all of these heads and depending which head is produced such as bare or complete and chamber size, it will get a different part number. For example, the 60579 is a complete Performer RPM (87cc) Round Port cylinder head based on the 6056 casting and the 60569 is the same head but bare head only, not a complete head.


The next question asked is flow numbers. Below is Edelbrock flow test results.

#61569 (D-PORT 87cc Chamber)Flow Numbers as tested by Edelbrock's SuperFlo SF-1020 flow bench @ 28" H2O
Valve Lift .100" .200" .300" .400" .500" .600" .700"
Intake 64 139 200 237 251 262 266
Exhaust 53 99 131 151 160 165 167

 

#60579 (Round Port 87cc Chamber)Flow Numbers as tested by Edelbrock's SuperFlo SF-1020 flow bench @ 28" H2O
Valve Lift .100" .200" .300" .400" .500" .600" .700"
Intake 72 138 198 239 264 275 -
Exhaust 56 106 141 163 172 185 -