[GtoFM]

Rebuilding a '64 389 tripower with 716 heads. I realize these aren't the best flowing heads Pontiac produced. Is there any bench test info showing stock flow and improved flow after mild or full porting? I'm not looking to do anything radical, just curious. Most likely end up with a 067 or 068 cam. Wondering if any porting would be a good investment for a pump gas daily driver.

[steve25]

These heads rework nicely, but for a novist porter you would be better off since they likely need a valve job to do the porting work first so you don't take the chance of nicking up a Newly done valve job during the porting work even though you could tape up the valve seats.

These closed chamber 389/ 421 non super duty heads need more work on the Exh side then the Intake, and Exh wise they also need work on the center Exh ports at the flange on each ports outside verticle wall.

The proper valve job done on both ports will pick up a needed nice chunk of low lift flow in and of itself.

In stock form on the Intake side these heads flow a peak Intake cfm of 175@28", stepping up to a 2.02" valve and opening up the chamber to a shape more like the 670 heads I have yanked Intake 250 cfm@28" at .600" lift.

A novist porter with some guidance, the right porting tools and time should be able to hit 210, or maybe even 218 cfm even with the stock size Intake valve!

This is about all the Intake flow you should shoot for if the Exh side will need to dump into stock log type Exh Manifolds, to tell you the truth, Intake Manifold wise I have never flowtested a 64 Trip set up on my flow bench so I am not sure it can support a head that can flow 218 cfm!
If nothing else though the short runner lenght set up by the placement of the bigger sized end Carbs helps out top end HP a good amount .