2.4S head flow rates

[BK911]

I just put a 2.4S head on the flow bench and got:

61 cfm @ .1" lift
118 @ .2"
169 @ .3"
196 @ .4"
201 @ .5"
all at 28" Hg.

Somebody got to these heads with a die grinder and didn't do a really good job. Not hateful, but not good either. Does anybody have a virgin head they've flowed? Of know where this information is? I'd be curious to see the difference. I am going to smooth them out a little this weekend and reflow them. Hopefully I can improve them a little.

BK

[JohnC]

Well these are'nt 2.4S heads but it is a start.
http://www.turbo911.com/forum/forum/display_topic_threads.asp?ForumID=6&TopicID=105&PagePosition=1

It will be interesting to note the differences between the ported and non-ported heads.

My suspicion is that even Porsche heads can be improved somewhat (flow increased)as a result of the manufacturing (casting) techniques.... the use of draft.

[BK911]

Very interesting. Initially I thought my numbers might be Ok assuming the turbo had bigger ports. But as it turns out the turbo has 32mm intake ports and the 2.4S has 36mm. The turbo valve is bigger though, so maybe my heads aren't that butchered afterall. Fortunately I've had a volunteer from the audience to send me an unmolested 2.4S head to flow. More data to follow.

BK

[jluetjen]

BK;

For kicks; it would be interesting if you could get your hands on a T or E head for comparison also since that is the head that most of the early cars were made with. I guess an SC head would really fill out the database for the SCWDPers.

Anyone have one laying around? I'm fresh out!

- John

[jluetjen]

Oh -- and one more thing!

BK; could you publish the dimensions of your "ported" head, for example the height and the width for each 1/2 inch in from the manifold face as well as a description of the finish. I picture would be cool too, but I'm most likely asking too much.

This is an excellent thread! It's good to get away from the "Which parts do I bolt onto my 2.0T to get 450 HP for less then $150?" type of questions and do something new.

[pwd72s]

I find this interesting as well. Jerry Woods was a speaker at a Rainbonnet seminar in '93...he said he spent countless hours on a flow bench, found it hard to improve the flow of a 911S head...IT seems the Germans would make pretty good drag racers here, most of the "tricks" had already been done...by the factory.

[Early_S_Man]

And ... just to amplify what Paul said ... the 2.2 'S' head was deemed suitable to use in the 2.4 'S' and RS 2.7 engines, without ANY modifications whatsoever!!! Same part number for all three heads!

[BK911]

I'm not disagreeing that the heads are great from the factory. But I'm pretty sure I can get something out of my heads that were already worked on. There's a few ridges and some scatter that can be smoothed out some. That's why I'm interested in original S head flow numbers.

If anybody wants to send me a stock T/E and/or SC head I would be happy to flow it and send it back. No die grinder involved!

And if anybody wants to donate a stock head to charity I'd be happy to see if I can make any improvements.

BK

[jluetjen]

The other thing that would make these flow numbers meaningful would be some maps of the cams. Has anyone ever mapped out the lift for an early S cam? How about any of the other cams? This would allow combining the cam data with the flow data to have a sense of how much air is flowing per degree of crankshaft rotation.

BTW; For kicks I pulled out my copy of "How to Build, Modify and Power Tune Cylinder Heads" by Burgess and Gollan and took a look at some of the case studies that they included with the book. (Note that they tested the flow at 25 inches of water). I've picked a few which have a single cylinder capacity similar to a 911's.

Ford Essex 3.0 V6 (Very ugly!)
Lift..Std....Mod'd
.1....39.7...43.4
.2....76.6...89.7
.3....94.9...124.0
.4...101.1..143.6
.5...104.0..152.1

Ford SOHC Pinto (2.0 4-cylinder)
Lift..Std....Mod'd
.1....40.5...48
.2....75.9...96.4
.3...103.8..129.6
.4...119.1..149.9
.5...127.0..157.5

Fiat Twin-Cam 8-Valve 1.8-2.0 4-Cylinder (Note similar concept Hemi head as the 911)
Lift..Std....Mod'd
.1....41.2...44.7
.2....87.9...89.3
.3...119.2..126.3
.4...125.8..145.4
.5...131.6..160.1

Ford 351 Cleveland 2V head. 2.041 inch intake valve.
Lift..Std....Mod'd
.1....48.93...58.65
.2....99.54..120.84
.3...145.7..170.91
.4...163.1..187.7
.5...180.3..187.22

If you read their notes, you'll see that I think is the biggest difference between porting a Detroit product versus a 911 head.

The rectangular port is too small to achieve a good blend into the throat area (even with a hump on the port floor)with this valve size. As the valve flow is improved, the flow finds it increasing difficult to negotiate the short turn, evidenced by the flow dropping off with increasing lift. Thinness of port walls precludes any further material removal. The fact that flow does not increase significantly from the original maximum -- merely being reached at lower valve lift values with additional modifications -- indicates that the head is port restricted with this size valve

I think that those comments kind of point out the biggest benefits of the 911 heads: No push rods or water jackets, so the ports can have a circular cross section and still have a nice direct path into the valves. The hemi design also allows big valves and a relatively small turn by the port from the manifold face into the valve.

That being said, I could picture a modified engine (high rev's or larger capacity) outrunning even the stock S heads. I suspect that this was the case with the 2.7 RS. Porsche also decided to expand the ports to 38mm even as far back as the 906 so that the airflow could keep up with the engine's demands.