case machining for 911 fan ring

[markvwguy]

I'm looking for machining information regarding taking the vent tower down to saddle 911 fan. My VW machinist of 50 years has never machined a case for a 260mm fan ring. He didn't say he wouldn't do it but needed indexing information. Anyone have a machining source in the Seattle area who has done this or who to send it to for machining.

Thanks,
Mark

[Lo Cash John]

I think it depends on what 911 fan shroud kit you’re installing. I know the kit sold by FAT Performance doesn’t require any machining however it’s to tall to fit in a bug engine compartment with the decklid in place.

What kit do you have?

[markvwguy]

Yes, I believe are correct as these fan shrouds are not standard, it would depend on the manufacturer. This would be more a machinist question I guess. What would be the tooling required to machine an almost 11" diameter radius into the case for the upright configuration.

Do you use a Bridgeport mill with a cutter large enough to cut the radius or it there a different way. The machine work I see seems to be a Mill with a large cutter.

[Lo Cash John]

I'm not a machinist and have no idea.

Do you already have a 911 fan kit?

[markvwguy]

I contacted Bernie Bergmann, he sells a cooling system for the 911 fan and shroud which will fit under the T1,Ghia,Bus engine compartments for T4 upright. Yes, the case has to be machined to remove the breather tower, and place the 911 fan ring onto. He sells a jig to index the case machining or send him the case he will machine.

[twodollardoug]

I imagine you would have to use his shroud then. To make sure the fan lines up with the shroud. Being the shrouds are semi custom, it would be difficult to mix and match to have everything line up.

[Lo Cash John]

Also the Bergmann kit is not TRUE Porsche parts. It is "Porsche Style". From what I understand, the alternator is a slightly modified water-cooled VW alternator and the ring/support and fan are his own design. I've never heard of anyone complaining about any parts failing but if you ever need a replacement alternator you need to know what to buy and what the necessary modifications are.

Also, we aware that ALL 911 style shrouds are know to over cool the 1-2 side of the engine and under cool the 3-4 side. Numerous folks have made and installed internal baffles to balance out air flow.

[markvwguy]

Do you think people see the temperature differences by having to use 2 different temperature plugs or someone actually has a head temp sensor on each cylinder? I've heard about the 1/2 cooling, have yet to see any temp numbers.

[twodollardoug]

I have an aircraft CHT gauge in my 914 that I use. I have my tangerine racing cooling system down to less than 10° from side to side.

[Lo Cash John]

A few folks have run tests over the years using multi-channel temp sensors. As I recall the largest measured difference from head to head was about 60* F. Some digging around here, Samba and Cal-Look Lounge found probably find some results.

[Lo Cash John]

I have an aircraft CHT gauge in my 914 that I use. I have my tangerine racing cooling system down to less than 10° from side to side.

Isn't that a horizontal fan kit?

[twodollardoug]

It is... But I think even temps can be achieved with the 911 shroud. Just depends on how anal you are and how many times you want to pull the shroud and make changes to the vanes. I think I pulled mine 2 or 3 times to get mine where it is.

[markvwguy]

I guess my question would be for folks who have a a temp sensor what temps are you seeing? And at what displacement XX by XX . I understand the +/- of the two and tweaking the flow.