[steve25]

For those folks running these heads that oiled thru the rocker studs there is hope for a boat load more power.

I had time over the last two days to port up a intake on a 9773845 casting .

I kept its 1.88” valve and 30 degree seat and let the chips fly .

I probably took as much time making 8 or 10 flow test as I did grinding on the intake port.

All total in terms of porting time and doing the chamber rework and valve job I guess I have 3 hours into this intake port.

Here’s the flow numbers, stock, Ported, flow gain produced.

In all fairness I did neck down the stem of the intake 1.88” valve to 5/16” like a modern valve would be.

.050”. ///// 33///// 45.5///// 12.5

.100”///// 70.2///// 71.7///// 1.5

.150”///// 104.8///// 111/// /6.2

.200”///// 133.2///// 133.9//// .7

.250”///// 150.3///// 156.8///// 6.5

.300”//// 155///// 175.8//// 20.8

.350”///// 158.7///// 194.6//// 35.9

.400”///// 159.7///// 206.2//// 46.5

.450”///// 159.7///// 210.7//// 51

.500”//// 159.7//// 213//// 53

.550”///// 159.7///// 214.3//// 54.8

Above .250” lift the port is flowing equal to or better then a stock 1967 and up D port head.

No, I have not CCed a this ported intake or a stock one but I will next week after I port up a exh port to report back on.

The port is still just kind of ruff cut also, the bit of shine seen is because a painted the port a medium gray to try and get rid of the bad glare I was getting with my phone camera.
Here’s some photos .

[mgarblik]

So what engine would that head have come on originally? I don't know the early casting numbers that well? In the very early days of NMCA, porting was not allowed in the "Pure Stock" class. I think they allowed a port match back like 1/2" and a valve job. Your % increase is impressive. It's interesting to note that stock head is effectively done flowing more air at only .300 lift. At least it doesn't back up like a few castings do. Also shows how putting a 45 degree seat on that head would take a bad situation and make it that much worse. Also explains why virtually all Pontiac cams had .400 lift. I had a heck of a time being competitive with 093 heads, no porting allowed. It was also very sensitive to fuel quality. I bet if I had your ported head, it would have made 50 more HP. Nice job on a weak factory head.

[PAUL K]

Nice!

[steve25]

Thanks for the Thumbs up!

This head was used on 3 or 4 different Hp rating 389 motors if I recall right, and at best with there stock flow numbers even making 300 hp would take a full on race motor.
The 093 casting ported up well can go over 245 on the intake side .

I think your battle that you had being competitive with the 093 or for anyone running these early pre 67 heads other then the 62 and 63 SD heads is how bad the exh side is!

These heads are what have gave Pontiac the bad rap of poor exh flow.
Many of even the 67 and up D port heads with the 1.77” valve no less the round port heads flow very close to a iron BBC exh with its much bigger 1.88” valve.

[tom s]

I think the 980s had one of the best if not the best D port exhaust.Tom

[694.1]

Pontiac's low lift flow is very evident. It also looks like you un-shrouded the crap out of the valves?
I can't wait to dig into my '57. Do you think the factory intake manifold would keep up?

[steve25]

I don’t think even the later factory 4bbl with the AFB on it would keep up with this level of flow, even if you could bolt it up.

The early tripower’s might, but I have never had one in my hands to check out no less flow test.

[tom s]

The early 61 alu SD single 4 NASCAR intake will bolt up to a 55-60 head.it has a water donut on it that would have to be plugged.Looks like a RA IV intake.Tom

[PAUL K]

Originally Posted by tom s

I think the 980s had one of the best if not the best D port exhaust.Tom

I'd agree.... The 980 has similar flow characteristics of a RAIV head when ported.

[Jack Gifford]

What bore size of the flowbench adaptor? Large chamfer for intake valve?

[steve25]

Jack it was flow tested on my 4.00" Bore adapter.

If your talking about the look of the chamber , yes I made up a valve seat stone to get the needed level of unshrouding that my flow testing was guiding me towards.

These early chambers curve back in on themselves on the spark plug side and there is nothing you can do about that without a big enough Bore size, so this is why using a limit of .550" lift and under is all you can port for, or maybe I should say getting the best average numbers up to .550" lift .
This is why I was flow testing at .050" steps.

I hear tell that Pete McCarthy ported a 980 casting up to 270 cfm for a fellow a while ago.

Does anyone know what the stock Intake bowl throat size is on that 980 casting?

This Intake port I have now in this 845 casting is at the max for a 1.88" valve / 30 degree seat, it's at 88% or 1.66".
So right now the throat is little bigger then a stock 67 and up D port head.

Anyway you can't go any bigger safely then this 1.66" unless you are ready to deal with hitting water.

Infact I am close on the roof now to breaking into the rocker stud oil feed passage

Anyway, I am on to making chips in the Exh port for a while today.

[tom s]

Nunzi has got a set of 980s to 300 I was told.Was not told the E side.That is the only set I have been told over 290.Tom

[steve25]

I don’t know about that 980 head doing 300 cfm if it was really tested at 28”, it might have been a higher test depression.

I mean a 2.02” valve will go 300 cfm, but the chamber shrouding on the plug side and the stock height of the short turn look very questionable to me, in fact I would think that a 55 degree seat would have to be used just to ease that plug side shrouding issue.

I wound love to have that 980 head in my hands just to measure up physically even if I could not prove it out on a flow bench .

[tom s]

High CFM heads as I remember were fitted with like a 2.09 intake.I have Dave Johnson’s (RIP) back up heads on my car and they are 260 heads.His number one heads I believe were 290 and I think a board member owns them.Tom

[Jack Gifford]

So- no chamfer at the top of the adapter bore by the intake? It seems like your unshrouding of the intake would benefit from such a chamfer.

[steve25]

Here are the flow results from porting up a exh port on this head.
These results are from a center exh port and there more twisted nature as compared to one of the end ports.

I did fill in the exh crossover with clay and shaped it to match the contour of the end ports.

I used a stock valve without a back cut which would have picked up 4 to 5 percent more flow up to about .250” lift.

Here’s the flow numbers.
Column are stock, ported and difference.

.050”///// 23.3///// 27////// 3.7

.100”/////. 50////// 51.7////// 1.7

.150”///// 74//////. 75.9////// 1.9

.200”///// 95/////. 101.7///// 6.3

.250”/////. 113.2/////. 125.6///// 12.4

.300”///// 125.2///// 143//// 17.8

.350”/////. 130.3/////. 159.4///// 29.1

.400”/////. 133.7/////. 166.2///// 32.5

.450”/////. 134.4//////. 170.2/////. 35.8

.500”/////. 134.4/////. 173.1/////. 38.7

.550”///// 134.4////. 175////. 40.6

What’s interesting to note is that even through the more sever 17 degree valve inclination angle of these early heads as compared to the 14 of the later heads has a negative effect on the flow, the bolt boss support on the roof of these center exh ports is not as flow degrading .

Just to note once again this is a stock valve with no stem reduction down to 5/16” and no back cut.

Also there was no gasket match done yet at the exh port flange.

.

[Jack Gifford]

Good improvement in exhaust flow!

[steve25]

Thanks Jack!
I did not have time to make another Exh flowtest with a tube on the end of the runner, but I will do so by weeks end.

Jack in regards to your previous question about the Intake valve notch being used / simulated for a flow test what I do is slide the head over on the Bore adapter so as to get the edge of the chamber right to the OD / edge of the Bore.

[steve25]

Jack here’s a close up of the chamber rework I did with a head gasket in place.

The OD of the silver marker line is where the stock head gaskets fire ring started.

[steve25]

Here’s a up date on intake port volumes and some other details between the stock and ported intake.

The stock intake port CC’ed in at 151 .
Quite small considering that these 17 degree heads have intake runners that are close to 1/2” longer then the 67 and up 14 degree D port heads.

The ported intake here that I have been posting about checked out at 168.7 CCs, so some 12% bigger.

The stock valve bowl throat was 1.410” in ID, this works out to 1.560 sq inches.

The ported valve bowl is now 1.66” which provides 2.16 sq inches, or a 17.5% increase.

Here are some other size comparisons between the stock dimensions in column 1 and the ported intake in column 2

Window height. 1.370”/////-1.500”

Window width. 1.475”/////-1.525”

Port width at push rod pinch. .920”/////-1.013”

Port height at flange 2.034”/////-2.043”

The short turn arc in the ported intake is mostly a .812” arc other then what the valve job forms.

With all of this work done I really did not grind on the floor at all other then to blend it in where the new short turn arc met up with the floor, and of course to widen it to work dimensionally with the bigger valve bowl throat.
I did a very small bit of clean up on the floor at the flange basically due to the added width I ground in there at the pinch .