[Stan Weiss]

Originally Posted by steve25

Here’s a handy chart for street / strip motors up to about 470 cid .
This is not for race only motors trying to live on the street.

Note that a stock 67 and up D port head is 154 to 155 CCs

Steve,
Do you know what head that is based on? Port volume can be an indicator of average CSA, but only when the ports have the same port center line length. So a High Port would have a longer port center line length that a standard location port.

Stan

[Jay S]

I recall an Engine masters episode and a Richard Holdener video where on a street engine (SBC and Fords) they kept the short block the same and installed different heads with bigger port volumes trying to get the port volume to kill the low end power. As I recall, the low end stayed the same, actually started higher with the bigger heads, about equal at peak tq, and but kept making more power with more and more port volume.

https://m.youtube.com/watch?v=PZSQ5K...dCB2b2x1bWU%3D

What makes a Pontiac different?

[Formulajones]

You guys and your tiny heads lol

[Steve C.]

Skip,
Go with the tiny Edelbrock Performer Pontiac D-Port Cylinder Head 87cc
204cc intake runner volume

"Many feel the 215cc intake port of our Performer RPM is too large for the street, but we've found that the long connecting rod and big crankshaft throw associated with the Pontiac V-8 tend to make them less sensitive to port volume. The RPM is a great head for street engines, and I pushed for a large intake port when developing the Performer D-port-one much like that used in our Performer RPM."

https://www.hotrod.com/how-to/hppp-1...cylinder-heads


.

[Steve C.]

Dyno testing Ported 6X Heads and Edelbrock D-port Heads

Engine Displacement: 467 ci
Bore/Stroke: 4.185 / 4.250-in
Comp Cams Xtreme Energy hydraulic roller
Duration At 0.050: 224/230-deg

6X - 550 ft.lbs. Tq at 3600 rpm / 492 hp at 5100 rpm

Edelbrock - 570.7 ft.lbs. Tq at 3500 rpm / 502 hp at 5000

Edit to add testing link: https://www.hotrod.com/articles/hppp...cylinder-heads

.

[performerrpm]

Originally Posted by Steve C.

Dyno testing Ported 6X Heads and Edelbrock D-port Heads

Engine Displacement: 467 ci
Bore/Stroke: 4.185 / 4.250-in
Comp Cams Xtreme Energy hydraulic roller
Duration At 0.050: 224/230-deg

6X - 550 ft.lbs. Tq at 3600 rpm / 492 hp at 5100 rpm

Edelbrock - 570.7 ft.lbs. Tq at 3500 rpm / 502 hp at 5000

.

thats the xr276 hr isnt it? lol i had that cam but thought it might be a touch small on my 467...thats pretty impressive with the 6x4s....im guessing no port work on d port edelbrocks?

[Steve C.]

Yes, tested the out-of-the-box Edelbrock castings. I presume it was the XE cam.

I added the link to the article in my post above.

A fwiw tidbit....
Many years ago my previous engine builder put together a 4.250 stroke for a friend using the Edelbrock round port 215cc runner volume heads.. No port work other than a cleanup.
Performer RPM intake with a vacuum secondary 750 Holley and headers. Cam was a small Crower HFT with 236 degrees intake duration.
On the dyno at the start of the pull it made 499.4 ft.lbs. torque at 3400 rpm.
At peak tq rpm it was 570.7 ft.lbs. and carried over 500 ft.lbs up to 5300 rpm.

[Stan Weiss]

Originally Posted by Stan Weiss

Steve,
Do you know what head that is based on? Port volume can be an indicator of average CSA, but only when the ports have the same port center line length. So a High Port would have a longer port center line length that a standard location port.

Stan

Does anyone know what the Pontiac "D" port intake port center line length is? The number I have is 5.0" which would be shorter than a SBC or BBC. For reference the number I have for a CV-1 intake port is 5.5".

Stan

[Jay S]

Originally Posted by Stan Weiss

Does anyone know what the Pontiac "D" port intake port center line length is? The number I have is 5.0" which would be shorter than a SBC or BBC. For reference the number I have for a CV-1 intake port is 5.5".

Stan

5” sounds close to correct on a standard d port. A SBC is about 5.3”, but also the intake manifold angle is different (10*) and makes it even more misleading. I think a BBC is about 6”. The modern LS has an even more shallow intake maniflold face angle and cathedral ports throw the port length comparison way off. It is not like comparing Apples and Oranges. It is closer to comparing Apples and Carrots. LOL

[Steve C.]

Posted here for conversation.....

Out of interest in 1998 Jim Hand did port modification to a Edelbrock 87 casting with the goal being to improve low-and mid-lift flow while maintaining adequate high lift flow.

Reduced port volume from the original 215-216 cc to 196cc
Reduced inlet port height from RAIV configuration to standard D port dimension
Changed inlet valve seat angle to 30 degrees
Reduced maximum bowl/throat size to 1.70" diameter

Measurement and verification was done using a Superflow 110 bench; final tests were performed on a Superflow 600 operated at 28" of water.
A control port was left as-received to use as a standard.

Testing was done throughout the entire lift curve thru 0.600" lift

Edelbrock port:

.100" lift 69 cfm
.200 139
.300 200
.400 245
.500 268
.600 272

Modified port:

.100 87
.200 164
.300 213
.400 250
.500 267
.600 273

If memory serves me right modifications were conducted to one port only and never ment for any production and/or track testing.

( Side note: The above modification was 27 years ago. A lot has changed within our Pontiac community since then.
Larger cubic inches, improvements in intake manifolds, "larger" camshafts becoming more of a norm, as are 500+ horspower combos dedicated to street use, etc, etc.
To many today their opinions have changed revolving the use of cylinder heads. )

.

[Steve C.]

I forgot to mention the Jim Hand modifications to the Edelbrock head was with the cooperation and approval of Edelbrock. It was done in order to improve low and mid rpm response and performance for street and street/strip engines, to provide improved power in the lower rpm ranges, and to eliminate the need to operate the engine at higher rpm in order to realize significant performance gains with the Edelbrock heads. Noting it was done to provide good performance on basically STOCK Pontiac engines.
Edelbrock furnished a new ready to run 87 cc head (actually two cylinders of a head – cut so as not to be used on a car). The modifications were for research only for both Jim and Edelbrock. As Bondo was used as the fill material.
There were some minor sources of possible error listed in his report to Edelbrock. But the comparison was considered valid.
The report was sent to Edelbrock along with the modified head. They found it interesting, but informed him that since their foundry was running at full capacity, there would be no second Pontiac head for better lower RPM street use.
Again, keep in mind this was 27 years ago.


.

[Jay S]

Originally Posted by Steve C.

Posted here for conversation.....

Out of interest in 1998 Jim Hand did port modification to a Edelbrock 87 casting with the goal being to improve low-and mid-lift flow while maintaining adequate high lift flow.

Reduced port volume from the original 215-216 cc to 196cc
Reduced inlet port height from RAIV configuration to standard D port dimension
Changed inlet valve seat angle to 30 degrees
Reduced maximum bowl/throat size to 1.70" diameter

Measurement and verification was done using a Superflow 110 bench; final tests were performed on a Superflow 600 operated at 28" of water.
A control port was left as-received to use as a standard.

Testing was done throughout the entire lift curve thru 0.600" lift

Edelbrock port:

.100" lift 69 cfm
.200 139
.300 200
.400 245
.500 268
.600 272

Modified port:

.100 87
.200 164
.300 213
.400 250
.500 267
.600 273

If memory serves me right modifications were conducted to one port only and never ment for any production and/or track testing.

( Side note: The above modification was 27 years ago. A lot has changed within our Pontiac community since then.
Larger cubic inches, improvements in intake manifolds, "larger" camshafts becoming more of a norm, as are 500+ horspower combos dedicated to street use, etc, etc.
To many today their opinions have changed revolving the use of cylinder heads. )

.

I think there is no question with the way his car was set up it would have went a little quicker with those port mods he did than a stock E head. The average flow was more after the mods. But he could have went a lot quicker if he would have been willing to change his engine more and put that effort to porting the heads to 320cfm, especially running an AOD. We would be talking about his 10 second car instead of it running in the 11s.

[PAUL K]

Originally Posted by Jay S

I think there is no question with the way his car was set up it would have went a little quicker with those port mods he did than a stock E head. The average flow was more after the mods. But he could have went a lot quicker if he would have been willing to change his engine more and put that effort to porting the heads to 320cfm, especially running an AOD. We would be talking about his 10 second car instead of it running in the 11s.

He tried a pair of aluminum d-ports and slowed down. He probably could've gotten in the tens if the car weighed less. He had an idea of how he wanted his car to perform and stuck with it. It's easy to fall into the little bit more gear, little bit more RPM, little bit more nitrous trap.

[Jay S]

Originally Posted by PAUL K

He tried a pair of aluminum d-ports and slowed down. He probably could've gotten in the tens if the car weighed less. He had an idea of how he wanted his car to perform and stuck with it. It's easy to fall into the little bit more gear, little bit more RPM, little bit more nitrous trap.

He was not a young man by the time he was trying that stuff either. I think if you sent Jim home in his younger days with a 535 AI2 block and some wide ports all I would have ever seen was his tail lights.