908/911 Air Screen Hats

[MoparBoy72]

908/911 Air Screen Hats

Here is my current random parts project. Some of you may remember the fog light seals I offered a few months ago. I have not forgotten about the requests for door seals either… This next item will be a mix of aesthetics and function. I have always loved the sound of my E without the air box on but I never felt right with open stacks. I guess these would be a stop gap. Now the stainless woven mesh will not filter to any vast extent, but it will keep major debris out. I was hooked by the covers on the 908’s that I saw at Road America this year and thought that a 6-cylinder version would be a nice piece. I am using my E as a template. These should fit all 72-73 MFI cars with plastic stacks (also you ’74 Euro Carrera guys too with 911/83’s).


I have a design fairly well ironed out. Currently, I have no provisions for the oil breather, etc (although I have a good idea for a fix). I like the rubber straps that the 908’s used to hold on their air hats. Any idea where those are from? Some kind of 356 hold down? Other wise I am looking at using four of the standard “hook clamps” to hold and seal the air hats. Time wise I am hoping to have some by the end of the year.


Currently I have two questions.

1) What is the highest operating temperature your 911 has been? Please state where the reading was from (factory oil gauge, infrared thermometer…etc.) and if you were in street or race conditions.

2) Is there any interest in these?

[Flieger]

I am very interested, as long as they do not end up costing as much as the real 908 pieces

My 911 never gets much above 190 on the original oel temperature gauge. I have a front mounted oil cooler to supplement the engine's. I normally see 180 consistently, never varying much over the course of a drive.

I live in sunny Southern California and have driven on some really hot days

I have 'T' plastic stacks so they do not fit the nice aircleaners for 'S' stacks. I want to get rid of the ugly plenum but do not want to modify my stacks too much. Can you make them fit with the ame style of clips that hold the plenum?

Great project!

[MoparBoy72]

I am very interested...Great project!

Thanks,

Those temps are in Fahrenheit, correct (if not i think your engine would have melted... )? I am going to do my best to use the existing clips that are on the stacks. As far as cost goes it is dependent on the number I make and secondly the materials (hence strange temp questions...).

[tfiv]

The rubber straps look similar to the SWB battery hold down.

[CurtEgerer]

Porsche did use these air screens in a factory street car!

The 914-8, of course.

The 3rd foto is a closeup of a 907 setup for reference.

Andrew - we'll be in Saugatuck, MI and South Bend area next weekend if you're up for a road trip.

[MoparBoy72]

Thanks for all of the input,


Varunan- Thanks for the DP info. I wanted to make these out of ABS and my main concern is operating temperature because at about 300 degrees (F) it has the consistency of rubber membrane. ABS can also get soft after 220 degrees F; I need to figure out if there is any reason that the engine compartment temperatures would exceed that.

Tom- Thanks for the info on the rubber strap

Curt – as usual those pictures are great. (If a GTO is a muscle car a 914-8 is a Supercar.) Only two 8’s ever made right? One was Ferry’s car and the other was for the US Porsche importer Max [blank].?

It looks as if the 907’s cut outs are drastically bigger than the 908’s (sans the mesh).

[MoparBoy72]

Fiberglass would handle a much higher temperature not only because of its polyester base but the glass fibers themselves add strength where the ABS plastic is not a composite and deforms. If you would like I can get some better temp. numbers on Monday.


There would be very little restriction on air flow with open Air Hats. The factory setup seems very restrictive at least from the aspect of open area for the air to enter. The only element that would provide the restriction to the Air Hats would be the screens themselves. I searched McMaster Carr last week and the options are wide open for woven stainless steel mesh (.1" open area to a few microns).


As far as tuning goes for the MFI; I personally would not be concerned as my E runs quite rich. In theroy, if the engine is getting more air it needs more fuel. I am not 100% on the metering of the MFI pump. I know that is uses the relative position of the throttle to meter the fuel using its interal "space" cam. It may be possible to find a shop to try to tune your MFI with an [wideband] O2 sensor but I personally have never heard of anyone that brave... I would guess that a properly tuned MFI system would be fine with this minor change; I have heard that mufflers are quite another story though.

[MoparBoy72]

I would assume that all of the cooling air that cools the heads and cylinders goes through the engine grille-->moved under the engine shroud by the cooling fan--->the air is then directed down through the heads and cylinders and exits under the engine.

As the engine warms up the heat does rise from the heads and can warm the throttle bodys too. With the plastic stack'd 911's there may be an advantage of keeping the intake air charge cool and not conducting the heat through the long intake runners.

You are absolutly right about the flow or the air entering the intake. The hats will cause some turbulance. You are also right that given a proper "frame" and rain shield one could just place an element over the stacks. But there is the problem. I as of yet have seen no design that caters to the plastic stack MFI cars. I guess "they" assume that if we were tracking these cars we would move to High Butterflys or Slide Valves.... .

[MoparBoy72]

You make a good point. I really like the nostalgia look that these may add. All of the Rennsport Cars really had a lot of trick bits that could really provide a good look with a certain amount of (Hp/weight) benefit although maybe not optimal for all out race use.

I may also experiment with these, like you said. I could just cut the frame and sandwich a filter element between the stacks and frame. Then also install ST/R grille rain shields like below.

[Jim Garfield]

I think that those straps might be the same ones used to hold the fuse box cover on a 356.

And for reference here is a close up the grille cover on that same TR: