906 fan housing measurment

[tadd]

Can anyone supply the OD, and a few pics, of a mag 906 fan housing. A pic that Chris_seven posted on the early S board shows a smaller OD around most of the circumference with a bump to a larger curverature fit the standard case.

I have an SC fan I'd like to put on the rotary table and cut down to 906 size. The SC gives a bigger alt (lots of lights in my future) and is aluminum. Oh ya, it's hard enough to find let alone the 906 unit .

t

[LM3929]

I have a previous post showing a 245mm fan housing with an insert filling it out dowm for a 226mm fan. the company that made the insert was Omni design, I think.

I have the housing and fan for sale if you are looking.

Lorne M.

[chris_seven]

Tadd,

I am not sure what you need to know.

If you are going to use the standard housing with the 226mm fan then it will fit a standard shroud without change.

The 906 shroud is clealry smaller in diameter than the standard shroud and it may not have enough axial clearance for the longer housing of the later fan.

I have a 906 shroud but I don't have a late fan to make the measurement.

[tadd]

Maybe I need to rephrase...

What I know:
1. 906 fans are 225 mm. So are 77/78 SC.
2. 906 fan housings are magnesium and are smaller in OD than the 77/78 SC which are aluminum.
3. 906 housings are hens teeth, 77/78 SC not too hard to find.
4. 77/78 SC plastic shrouds use the common larger OD used on the 250 and 245 units.
5. 906 fiberglass shrouds don fit 245 mm housings.
6. 906 fans run at a 1.3:1 ratio while the 77/78 SC fans run at 1.8:1 and move as much air as the 245 mm fan at 1.67:1.
7. SC alts put out more juice than the 906 alts.
8. Al tends to hold up better over time than Mg.
9. The OD difference is only around part of the 906 housing since the housing still has to interface with the case which was designed for the larger 250/245 mm housing OD.

So what I want to so is take a 77/78 SC housing on the rotary table and reduce the OD (part way around) to that of a 906 housing so I can use a 906 shroud. Thus I need to know how much material to remove. Ultimate question: what is the OD on a mag 906 housing?

Thanks a bunch for the replies!

t

[TRE Cup]

First off, i don't have the dimension you are looking for, but to further the discussion a little:
Your goal is to have a 906 fan shroud with 906 diam ring and small fan, so you have the correct early look- kind of a doh ! assumption since you posted your list, but just making sure. You are aware, i'm sure, of no oil cooler duct on the 906 shroud. They did not need them as there was a racing filter in place of the engine cooler. So if you elect to run the engine cooler, as they used this shroud on the 2 liter 911, i hope you have an external cooler of large enough capacity to compensate for this

Fwiw- we have molds for twill cloth shrouding / surrounding "tin" w and w/o overlay oil cooler duct in standard 911 diameter. Series 900 / damon might have a mold for the 906 size, Crawford for sure has them too

I thought of machining a SC ring , like you are thinking of doing, but i was not sure the material left would be up to the task of supporting the alternator long term. Seen enough mag rings cracked to influence me that way. Also i would not be getting the correct outer diameter details that are part of the 906 look ; no casting numbers, upturned front lip that matched the original part, and other details.

omni design is no longer making the ring, and they had their name engraved on the lip face anyway. Crawford composites makes an aluminum part. We got it from them, and the correctly sized alternator from Dave Aase (aussie built unit with 95 amp output in various casing sizes) . For authenticity we had the ring black anodized. As long as it is not subjected to a lot of sunlight, it will retain its "original magnesium" look. This is what we installed on the light ivory ST tribute featured in excellence.

p.s.- chris 7 is right on the length of the later alternator and the downward curvature of the shroud= not enough room. i forgot about that

Good luck with your project
Dave

[tadd]

TRE Cup:
You nailed it. I can't do it all now, but I'd like to have something resembling a 906E like when it's all said and done... But 2.8L in size with lots of modern goodies inside (Steve did his head magic) . Early 67 case, early ceter lube cams (3.8 rsr on 102LC cam grinder specials), ect. Ill have to live with TWM TBs for now cause I miss the car and want to drive again! I'd like to find slides and the single row MFI pump eventually when $$$ allow. Will be using an 009 for now. Will be using a 964(?) oil filter fitting in place of the pressure side engine cooler.

I'll never make concours perfect so looks close with upgrades is good enough for me.

I figure it will all go up in a build thread once everything is ready for assembly. I hate 6 year builds .

t

[tadd]

Heres the pic Chris_Seven posted on the early S registry... Notice the smaller diameter isn't a full 360. Also I can't tell if the smaller diameter goes all the way to the lip.

[Gunzel]

Tadd

I have a 906 fan housing . I live in the Philadelphia western burbs around Coatesville. Come up and see it and measure it if you would like.I also have a 906 slidevalve and pump.

Mike