Head Porting

[porschedude996]

I’m building a 3.0 with a couple of mods, euro pistons (9.4:1), 964 cam grind, but otherwise stock. Is there any good reason to clean up the ports? Smooth out the walls…

[john walker's workshop]

Textured intakes and smooth exhaust. Smaller port intakes get better low end/midrange poop, bigger gets more top end. Compression and cam choice helps both. Are you streeting or racing 99% of the time? What year are the heads?

[porschedude996]

Originally Posted by john walker's workshop

Textured intakes and smooth exhaust. Smaller port intakes get better low end/midrange poop, bigger gets more top end. Compression and cam choice helps both. Are you streeting or racing 99% of the time?

99% Street with some WOT back road fun. 1983 head date.

[stownsen914]

I'd like to know more about this "low end/midrange poop" we're speaking of

[john walker's workshop]

More port velocity basically.

[stownsen914]

Gotcha. I thought it might've been a typo actually and thought I was making a funny. Joke's on me lol.

[john walker's workshop]

I worked at a local Porsche dealer when the SCs came out. Pretty soon some new owners complained that the bottom end "poop" was disappointing, compared to their previous 2.7s. 78/79 big port 3.0 vs smaller port 2.7.

[PeteKz]

"poop" = grunt. There's a potty joke in there somewhere.

[AndrewCologne]

Originally Posted by porschedude996

99% Street with some WOT back road fun. 1983 head date.

99% Street? Then just switching to 964 cams won't give you real satisfaction as you really need to rev up to high rpms to feel the benefit. For primarily street usage better would be upgrade to 3.2SS, keep the stock SC cams set them to 1.4-1.7 instead of 0.9-1.1 (yes for even better torque at mid revs and use an electronic ignition advance system which gives you the spark where it ends in an optimal combustion.
If you benefit from Premium gas avalablity in your region, the you cab even choose pistons with a CR of up to 10.5:1. All last mentioned can be combined with 3.0 sized pistons as well.

[ryanrobert]

Originally Posted by porschedude996

I’m building a 3.0 with a couple of mods, euro pistons (9.4:1), 964 cam grind, but otherwise stock. Is there any good reason to clean up the ports? Smooth out the walls…

You have to clean up the ports , i assume

[porschedude996]

Originally Posted by ryanrobert

You have to clean up the ports , i assume

Stop following me.

[Castro911s]

That textured intakes is pain in the rear .

[Speedy Squirrel]

Speedy sez:

1. Poop is for litter boxes, not Porsches
2. Cam duration and overlap are also players for low end torque, more so than port size, imho
3. Put some gears and a good clutch in it. Makes port velocity less important. You will be less likely to be treated to a distant view of my taillights.

The proceeding comments were entertainment, like vixens from Qatar.

[Henry Schmidt]

Venti-port...the best of both worlds.
Years ago we had an over ported (43mm, 3.6 head, 104mm bore) and it was useless under 3000.
We got the idea of reducing the size of the port by inserting a sleeve.
I was reading about air flow, fan speeds and Bernoulli's principle.
It seemed to me if we inserted a venturi onto the port and lengthen the port by extending the sleeve that we might get greater flow with reduced port size, 38mm was where we landed.
Every head guy to a man said it wouldn't work. I'm stubborn so we tried it.
We sent the head out to a well know head specialist along with a factory 3.0 RSR head (43mm intake). The results were amazing. The venti-port head flowed better at 2-4.5K and about the same all the way to 7K. At 7K, as expected the flow dropped substantially. The engine we were building had cams that were pretty much all in at 6800 (DC60) so we tried them out.
Although we never dynoed the engine it did break a Mendeola transaxle first time out.
We later built a few of these venti-port engines for European rally 3.0 cars and the engine made 305 @ 7400 with 9.5:1 compression and 46 PMO carbs.

[Old H2S]

Mother Mopar did the same thing in the '60's, they made drop in manifold to head gaskets with screens molded in for big block drag engines. Run the screens on the street to the track and pull the gaskets and drop in regulars for the race. I found a set in a '69 Dart "street car" I bought that had the infamous 509 cams in it that were terrible for street driving but ok with the screens in. Later I would make them for Mustang boys that had over ported heads on the street which seemed to be common.

[crashmy911]

I,had a 78 sc motor I built w 8/5 to 1 compression and I used 964 cams. The motor really sucked. I drove car at the track too. It was good up top but nowhere else.

[porschedude996]

Henry, you are amazing. I enjoy your every post.

Originally Posted by Henry Schmidt

Venti-port...the best of both worlds.
Years ago we had an over ported (43mm, 3.6 head, 104mm bore) and it was useless under 3000.
We got the idea of reducing the size of the port by inserting a sleeve.
I was reading about air flow, fan speeds and Bernoulli's principle.
It seemed to me if we inserted a venturi onto the port and lengthen the port by extending the sleeve that we might get greater flow with reduced port size, 38mm was where we landed.
Every head guy to a man said it wouldn't work. I'm stubborn so we tried it.
We sent the head out to a well know head specialist along with a factory 3.0 RSR head (43mm intake). The results were amazing. The venti-port head flowed better at 2-4.5K and about the same all the way to 7K. At 7K, as expected the flow dropped substantially. The engine we were building had cams that were pretty much all in at 6800 (DC60) so we tried them out.
Although we never dynoed the engine it did break a Mendeola transaxle first time out.
We later built a few of these venti-port engines for European rally 3.0 cars and the engine made 305 @ 7400 with 9.5:1 compression and 46 PMO carbs.