[steve25]

This is only the second time I have had my hands on a pair of these heads.
The first time was before I had
My flow bench, but this set will not escape getting flow tested before and after my bowl porting work.

I also have the heavy as hell intake manifold that I want to flow test at least the 4 runners off the shallow side of the plenum.

Here are a few photos and a review of pertinent size info.

I will start with the intake port details, then the exh port and also make some comments on both.

INTAKE.

Intake bowl throat, very near exactly 1.70 x 1.59” as can be seen in one of the photos with the template sitting right on top of the valve guide.

This works out to 2.700” Sq in.

Intake seat
45 degree with a 2.075” OD.

Seat width .088”

1st bottom cut 60 degree, width .128”

2nd bottom cut 70 degree with a depth of .744” on the exh side of the bowl and .205” on the common wall side of the bowl.

What there is of a short turn arc is .996”, and there is not much overall short turn height, in fact the 6X castings have way more height then these heads.

Now I can see why these can not be ported into flow rates like the RA4 heads without building up the short turn.

Port window height at crown 1.925”.
This is quite tall and indeed breaks into the rocker stud hole.
Window width= 1.407” on the floor, 1.307” on the roof.

Note how squared off the floor is at the start of the windows.

This is a larger version of what the 6X heads have.

This ruffly works out to at best 2.67 Sq inches since I did not subtract for any corner radius.

Port height at flange = 2.265”.

Minimum Port width at center height of flange = 1.082”
Chamber depth on shallow side = .242”


EXHAUST


Valve bowl throat = 1.465”, 1.685” Sq inches.
This is only 67% of the massive area increase at the window as you will see in a photo.

Seat 45 degree.
Seat OD. 1.765”
Seat width .055”
Bottom cut 70 degree with a depth of .312”

This 70 degree bottom cut is a radical change from Pontiacs normal 90 degree cut in relation to the chamber floor.

The minimal amount of short turn arc these heads have looks like .992”.
With that said these exh ports have a good amount of overall short turn height for a deep chamber low compression head, that may exceed the good amount of what the 6X heads have going on.

Actually these SD heads may have more height then what the 6X heads have.

Window height = 1.565”

Window width = 1.505”.

Average width at flange = 1.735” or 2.364” Sq inches.
This amount of square inches and more importantly the amount at the window as compared to the bowl, if nothing else in my experience will make for a big velocity differential between the roof and floor of the exh runner, and that’s never good for reversion.

We will see when start flow testing later in the week.

I will also be making port molds .

There are two more photos I need to post separately after this.