[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

[Half-Inch Stud]

That is good.

I found it better to convert to runner Width * Height. Reveals the pushrod bulge choke point real quick.

Derived from the choke--RPM equation.

[PAUL K]

Interesting thanks for sharing

[steve25]

Welcome folks.

[Skip Fix]

But those "big" 215 cc E head ports make them lazy on the bottom end

[steve25]

Yes your statement is true.

[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


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[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.

[77 TRASHCAN]

Originally Posted by Skip Fix

But those "big" 215 cc E head ports make them lazy on the bottom end

I remember Jim Hand saying that most of the more common "D" port heads had 153 cc intake runners...

I've heard it mentioned here a couple of times that it's nearly impossible to put too much cylinder head on a Pontiac.

I know these to be in their specific contexts.

My knowledge is a lot of what I've read here, and from other Pontiac enthusiasts. Just wonder where these 2 statements currently stand....

[Steve C.]

Jim Hand's comment from YEARS ago....

6X-4 heads ported exactly as shown in my book except bowl enlarged to 1.72” rather then 1.69 to pick up flow. Ports purposely kept small as possible for max torque throughout entire RPM range – average of 170 cc per port and definitely no “choke” at the RPM we run.

This was a 473 cubic inch engine. The car was built for street use and bracket racing, and stressed consistency for track.


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[steve25]

Unfortunately dyno’s can’t pull down to below 2400 rpm where drivability issues would show up on the street in high gear.

[Formulajones]

My thoughts that have served me well leans more towards the larger side. Pontiacs make such a boatload of torque anyway, on top of that so many here complain of traction and either don't want to or can't invest time and money in the suspension to make it work so there's that. You don't need 500 ft lbs at 2000 rpm or even 3000 rpm for that matter. Especially if your on rock hard street tires. If you can move it up the scale with head and cam choices a street car is better off, easier to control and more manageable.

That said, I like grunt and the more the merrier but I'll set the rest of the car up to use it. However I've had no issues making low end grunt at lower RPM with larger cylinder heads and there are tons of examples of that from all kinds of combinations.

[Skip Fix]

Originally Posted by steve25

Yes your statement is true.

What that a 215 cc port on a 455 will be lazy?

And what size are SBC 350 Vortec TRUCK heads in relation? 185cc! 327 461s-161-172! Smaller motors the Vortec truck heads larger the 461X at 172 larger than most D ports. My Vortec headed truck hauled my trailer and 3900 lb TA form Houston to Memphos and Atlanta ! Truck was 5575 when I rolled it on the scales at one track.

Wonder what size the 5.3 LS motor on my wife's Avalanche that hauled her horse trailer and 1200 lb horse!

[Steve C.]

This reminds me of a statement made by a well known Pontiac persoality in our community, during a discussion about the HUGE ports when the Edelbrock head first came out.
He was running 11.76 et with mild ported factory heads and a 234 degree HFT cam at the time.

His comment..

"I do need a set of E heads so I can run a 4000 stall converter, 4.10's, more cam and wind it 6500 to run what I do now!"



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[Formulajones]

Huge ports, hahaha