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The motor I'm building for my 951 started life as a very early NA block, and hence, I can't install a 951 AOS due to the different stab sizes into the block.
The issue is the vent line that comes out of the turbo mount:
Obviously the oil drains primarily into the pan. Is this vent line therefore even necessary?
If so, has anyone modified an NA AOS to have a nipple for that line? I have a somewhat charred 951 AOS I can salvage the nipple from and perhaps epoxy it to the NA one, after cutting or melting a hole in it.
My other option, I suppose, is running a standalone catch can for that vent line. Hooking it right into the manifold would obviously be a huge mistake.
Do you plan on using stock turbo pistons in that block? You may want to check piston tolerance group sizes in relation to the bore of that block. You may have a 0 group block, and I have only seen group 1 and 2 stock turbo pistons. The 0 group bore is the same size as the group 1 pistons if I remember right.
I have a group 1 block, and group 1 turbo pistons. I also coincidentally have 3x group 0 and 1x extra group 1 pistons, all low mile 951 parts. somebody please buy them
The reason I'm using this block is because it's very low miles and the bores are mint. My 951 block is an unknown quantity and the bores are less than perfect, and this motor is done once I drop in the pistons/rods and install the head.
If so, has anyone modified an NA AOS to have a nipple for that line? I have a somewhat charred 951 AOS I can salvage the nipple from and perhaps epoxy it to the NA one, after cutting or melting a hole in it.
It's very possible. I was actually just talking about this same issue with a friend a few days ago because I inadvertently bought a 944 AOS for my new turbo motor. There are plastic weld products which are designed for heat and vibration which are permanent solutions. You can remove the top of the AOS which will allow you access to both sides of a drilled hole and allow you to clean it up and ensure there is a secure connection.
In the end, I elected to grab a turbo AOS because I had one come available at a reasonable price but the option to add a nipple is very possible.
Awesome thanks!
What are the implications of not running the vent line at all? My oil feed is coming from the oil pressure sender and the only thing standing between it and the turbo is a restricter.
It helps the oil drain out of the turbo because the turbo is mounted high relative to the sump, and the turbo oil drain is below the oil level.
Think about when the car has been sitting for a few days, all the oil in the turbo will have drained out because of gravity. The pressure side of the system is "sealed off" more or less so there'd otherwise be a vacuum due to the drain...so some air can come in to relieve the vacuum.
Same thing for when you start the car up again...air is in the drain line with no way out (because the drain is below oil level) so if pressurized oil were to start flowing into the line it would "get stuck" on top of the air column, building up oil in the journal, leaking past seals, etc. So the AOS vent lets that air get out...
I'd look for a sort of "bulkhead" thread-type fitting rather than trying to epoxy - don't know exactly the chemistry of the AOS plastic and how it might react to epoxy, and how the epoxy might react with oil.
Search for "uniseal" and buy one with the same ID as the vent line. Fit the uniseal and install a short, about 2in, pvc pipe with an OD the same as your vent line ID. Fit vent line to pipe and secure with a clamp.
I've used uniseals in other similar situations, they seal tight with only pressure and are resistant to most every chemical.
Edit: forgot to say, they conform well to curved surfaces.
Interesting. My main issue with inserted/bung fittings, like bulkheads, is the entry point of the nipple into the AOS body is nearly tangent. If a uniseal was used, looking at it from the point of view of the incoming vent line hose, it would be an ellipse.
With that said, maybe the answer here is to cut the vent hardline, and run silicone line to a nipple that I can insert at a more reasonable angle. That would allow a uniseal as laid out above and I can't see any downsides.
...With that said, maybe the answer here is to cut the vent hardline, and run silicone line to a nipple that I can insert at a more reasonable angle. That would allow a uniseal as laid out above and I can't see any downsides.
That sounds like a plan.
I'm not keen on the other options mentioned here. Epoxy will not last, it is not flexible and will crack, leak and break off with the slightest vibration. A threaded bulkhead fitting would work but you would have to find or make some curved rubber washers or the like to make a threaded fitting fit on a curved surface.
It depends on how the air flows out of the turbo drain.
The AOS depends on a "vortex" inside, which is why the block port is also tangential.
Sticking the fitting in the wrong place might upset the spinning air inside...
Also, silicone tends not to play nice with oil/oil vapor over time.
11-03-2016, 03:01 PM
AOS modification brainstorming
